October 1

Resolved

Can anyone, by any chance, supply a 'free to use' (ie Public Domain or Creative Commons commercial-permitted) picture of a Pthirus gorillae? For use on that article. I can't find one; thought possibly people here might know of other sources. Cheers,  Chzz  ►  00:29, 1 October 2010 (UTC)[reply]

Is this issue resolved? You seem to have found a picture Nil Einne (talk) 06:23, 1 October 2010 (UTC)[reply]

It is indeed; sorry for not marking it as such sooner. Someone else found a pic, which I was able to retouch a little. Nothing great, but it'll do the job. Thanks,  Chzz  ►  07:00, 1 October 2010 (UTC) (now marked as resolved)[reply]

I've discovered that you can transfer the image from a normal sheet of inkjet photo paper onto another surface... I was experimenting with letting the photo prints soak in cold, warm, and boiling water when it turned out that boiling water allows the top, slimy layer of the photo to loosen enough that it can be burnished onto a sheet of watercolor paper.

The thing is that after boiling these prints for a while I noticed a smell, not overpowering but noticeable. Obviously some of the chemicals that hold the image to the page were being released into the air as they dissolved and evaporated.

The decayed appearance of the images that result from this technique are very well suited to the ideas I'm working with (I'm an art student), and the materials are much cheaper than a Polaroid camera and the film for it would be (as in a Polaroid transfer). This technique on a larger scale would be ideal for an upcoming project, but I have no idea what chemicals I'm exposing myself to in the process. Although I've done some basic checking on Google, no info seems to be forthcoming. Does anyone here have have any knowledge of the chemicals involved? Are they harmful on skin contact or if inhaled? Should I invest in a respirator?

I've contributed to Wikipedia articles often, but I've only used the ref desk a few times. Forgive me if this post is too forum-ish. Also, please don't link me to Inkjet transfer- those techniques involve specially made transfer paper and produce a flat and uninteresting image surface. Thanks, Lithoderm 02:24, 1 October 2010 (UTC)[reply]

Forgot to mention - I'm using an Epson RX680 with Claria Hi-Definition Inks and standard glossy inkjet photo paper from Staples. Lithoderm 02:30, 1 October 2010 (UTC)[reply]

My suggestion would be to look for the MSDS of the inks you're using. If they aren't available online, try asking Epson. Nil Einne (talk) 04:27, 1 October 2010 (UTC)[reply]

Thanks, I wouldn't have thought of that. Lithoderm 08:24, 1 October 2010 (UTC)[reply]

It is possible, of course, that the chemicals causing the smell are being released from the paper, though I expect that you have checked this. Dbfirs 10:03, 1 October 2010 (UTC)[reply]

Lithoderm did mention the type of paper so it may mean they're thinking of that too. However I don't know how well that can be examined more, I don't think there would be an MSDS for the glossy paper. The best option may be to try boiling printed normal white paper. If you still get the smell then you know the smell isn't coming from the paper. (Whether you can use it for transfers is irrelevant.) Of course you could get nasty stuff that you aren't smelling. However I have doubts there would be anything that bad in glossy paper. Nil Einne (talk) 12:13, 1 October 2010 (UTC)[reply]

The MSDS for the ink is here. It says that "intentional inhalation overexposure to ink vapors may result in respiratory tract irritation"- I suppose this means that I'd have to be huffing it for it to do any damage. Dbfirs is right to mention the possibility of the paper being the culprit - I have looked for information on that already, but as Nil Einne notes there doesn't seem to be an individual MSDS available for it. A controlled experiment would be a very good idea though. I may just end up borrowing a respirator from someone, or using a portable burner and doing the boiling outdoors. Lithoderm 15:18, 1 October 2010 (UTC)[reply]

Sounds like you figured that out on your own! Cheers! —Preceding unsigned comment added by 165.212.189.187 (talk) 15:34, 1 October 2010 (UTC)[reply]

I am a librarian at a small school in Colorado and one of our students needs biographical information, contributions to scientific field, and a photo (if available) of Agnes Stroud Lee. We know she was Native American.75.173.217.192 (talk) 03:10, 1 October 2010 (UTC)[reply]

Well there's this booklet about her for starters. WikiDao ☯ (talk) 03:19, 1 October 2010 (UTC)[reply]

Her full name appears to be Agnes Naranjo Stroud-Lee. There is not a Wikipedia article about her, but typing her name into google brings up some promising results. For the record, it looks as though she may very well meet the guidelines at WP:BIO, which means there possibly should be an article at Wikipedia. There is at least one full book-length biography of her named Scientist from the Santa Clara Pueblo, Agnes Naranjo Stroud-Lee and Amazon appears to sell it. this page has a very short blurb about her. Near as I can tell, she was a biologist who worked for Argonne National Laboratory, studying the effects of radiation on the body. A google search turns up a few nuggets. --Jayron32 03:25, 1 October 2010 (UTC)[reply]

knowing that 1 ppb is 1 x 10 (to power of -9) how do I work out what 1200ppb is?Wyburn (talk) 04:59, 1 October 2010 (UTC)[reply]

Try 1200 x 10^-9 or 1.2 ppm. Dolphin (t) 05:19, 1 October 2010 (UTC)[reply]

Regarding "how", 1200 x 10^-9 = 1.2 x 10³ x 10^-9 = 1.2 x 10^3-9 = 1.2 x 10^-6 = 1.2 ppm.

See Scientific notation#Basic operations. -- 111.84.200.184 (talk) 14:02, 1 October 2010 (UTC)[reply]

Or 0.00000012% --Chemicalinterest (talk) 12:07, 1 October 2010 (UTC)[reply]

No, it's 0.00012%. Gandalf61 (talk) 13:44, 1 October 2010 (UTC)[reply]

For questions like this, Wolfram Alpha is quite good [1]. In this case the input '1200ppb' is converted to "1.2 grams per metric ton" which is easy to relate to if you have trouble with exponentials. EverGreg (talk) 13:35, 1 October 2010 (UTC)[reply]

Note that converting 1200ppb to "1.2 grams per metric ton" is only valid if the ppb is weight/weight (admittedly the most common), but not if it is volume/volume or weight/volume. -- 140.142.20.229 (talk) —Preceding undated comment added 17:27, 1 October 2010 (UTC).[reply]

If you have trouble with exponentials, slowing down and writing out intermediate steps can help. E.g.:

1x10¹ = 10
1x10⁰ = 1
1x10^-1 = 0.1
.
.
.
1x10^-8 = 0.000 000 01
1x10^-9 = 0.000 000 001

And now I find it helps to line up your 'columns', like when you used squared paper to write out problems in primary school, keeping your hundreds, tens and units straight!

So, if it were just 9 x 10^-9, you could write:

0.000 000 001
0.000 000 009

keeping your units lined up. So you'd know 9 x 10^-9 = 0.000 000 009

Whereas, if it were 90 x 10^-9, you'd write:

0.000 000 001
0.000 000 090

keeping your units lined up. And you know you can write that without the final 0, so 90 x 10^-9 = 0.000 000 09, or 9 x 10^-8

In the same way, 1200 x 10^-9 can be worked out:

0.000 000 001
0.000 001 200

same as 0.000 001 2

So, 1200 x 10^-9 = 0.000 001 2, so 1200 x 10^-9 = 1.2 x 10^-6 (a nice way to see it) or 12 x 10^-7. And, if you know that ppm is 1x10^-6, you can rewrite from ppb to ppm! As you do more of this sort of thing, you can start to skip steps.

I hope this helps with where you were confused. 109.155.37.180 (talk) 14:27, 1 October 2010 (UTC)[reply]

what would happen if, someone having gotten the numbers slightly wrong, the stars Epsilon Eridani and Luyten 726-8 actually collide in thousands of years time, rather than just passing very close to each other?

148.197.121.205 (talk) 14:37, 1 October 2010 (UTC)[reply]

This is interesting because Luyten 726-8 is a binary system. There are many models of interstellar activity in which a binary system reacts to a collision by having one object fall into the collision and the other flung off into space (or at least a wide orbit). Star collision is considered rare (see note in star), but there are some theories that a star collision can create a blue straggler (also noted in the star article). -- kainaw™ 14:52, 1 October 2010 (UTC)[reply]

Yes, it is possible, but when you think of the word "close" as referring to two peas a mile apart, you can see that the chance of a collision is slim at best. --The High Fin Sperm Whale 17:35, 1 October 2010 (UTC)[reply]

Even without a collision, if there is any life in the Epsilon Eridani system, it could be disturbed by the perturbation of comets by the binary star close encounter. If two stars do collide, there is the chance for a supernova. However, a star actually colliding with an approaching star rather than just swinging by in a fractional orbit would be exeedingly rare, as evidenced by the future approach of Gliese 710. ~AH1^(TCU) 20:13, 1 October 2010 (UTC)[reply]

If they collide it won't be because someone got the numbers slightly wrong. The stars are not under navigational control of us humans – their trajectories became inevitable at the time of the Big Bang and ever since then, and into the future, they merely conform to what we now know as the laws of physics. Dolphin (t) 04:29, 2 October 2010 (UTC)[reply]

You are misinterpreting. If they collided, it would imply that someone had gotten the numbers wrong. --Anonymous, 07:13 UTC, October 2, 2010.

If two, or perhaps three, stars did collide, would they merge to form a single much larger star? And would that be so unstable as to explode, causing terrible destruction across a broad expance of space? And would the matter and energy thrown off from this explsion get drawn into other stars, causing them to grow to a less stable size and explode themselves, setting off a chain reaction and ending all life as we know it? 148.197.121.205 (talk) 20:14, 2 October 2010 (UTC)[reply]

Three stars colliding at the same time is almost impossible. However, the collision would rip both stars apart a fling the material everywhere, however, it would coalesce into a large star (although some material would be lost). And it depends on the type of star colliding; two small red dwarfs would probably just make a larger red dwarf, however, two blue supergiants colliding would probably go supernova. For them to go supernova, it takes some very special conditions. Most stars will never go supernova, so if a small group of very large, young stars were together, it might cause a chain reaction of two or maybe three stars. And you have to remember, a supernova is comparable to a pea causing a hundred foot long explosion. This may seem large, but when the next star is a mile or more away, then you can see there is little chance of any affect on one to the other. --The High Fin Sperm Whale 05:53, 5 October 2010 (UTC)[reply]

Following on from the ice cube post above, is it practical to use Ice as a self-destructing untraceable murder weapon? Scenarios :-

1. Jamming an ice cube into someone's throat so they choke.
2. Using a large piece of ice to inflict blunt force trauma
3. Stabbing someone with an icicle

Would a forensic scientist (or equivalent) be able to detect the murder weapon used? It's harder to prove murder if you don't have a weapon so would this increase the chance of evading justice? Exxolon (talk) 19:14, 1 October 2010 (UTC)[reply]

(edit conflict)Depending on the length of contact, ice does cause damage to cells. An astute or particularly observant pathologist might see it, might look for it. I seem to recall something about murder via ice (an actual case) being discussed in one of Robert Ressler's books (true crime; he helped found the Behavioral Sciences Unit at the FBI) but I cannot for the life of me remember which one, and I no longer own the books. → ROUX ₪ 19:22, 1 October 2010 (UTC)[reply]

Not exactly what you're asking, but there's a Roald Dahl short story, Lamb to the Slaughter, about a wife who kills her husband with a frozen leg of lamb and then roasts it, feeding it to the detectives who come round to investigate. Mikenorton (talk) 19:21, 1 October 2010 (UTC)[reply]

Unless the icicle was particularly large and thick, I think it'd just snap. Method A seems a little impractical because you have to be able to get that close to the individual, and then enforce that they don't just bring it back up. The middle one is certainly possible if you can find a piece of ice heavy enough to hurt but light enough to lift, but I'm not sure from a forensic standpoint. I can't imagine any reliable DNA evidence could be found in a puddle of melted ice, or even if the ice stays at all (it may evaporate before the forensics guys get there). Regards, --—Cyclonenim | Chat  19:25, 1 October 2010 (UTC)[reply]

Well, for method A perhaps don't use an icecube, but you could cram a large amount of crushed ice down the intended victim's throat. Googlemeister (talk) 19:29, 1 October 2010 (UTC)[reply]

Tangent - why the hell has this question been tagged as "may be inappropiate"? I don't appreciate those kind of insinuations about me Ludwigs2, care to explain? Exxolon (talk) 19:31, 1 October 2010 (UTC)[reply]

• My guess is that it's tagged because it's a discussion of what would be a criminal act. Plus, answering the question arguably involves giving both medical and legal advice. --M@rēino 19:48, 1 October 2010 (UTC)[reply]
  • plus it could incite angry responses from people who are (rightfully) concerned that you are specifically asking about ways to murder someone. It wasn't about you, it was about your question (I assume you have sufficient perspective to recognize that the question could be interpreted in some very bad ways). --Ludwigs2 19:52, 1 October 2010 (UTC)[reply]

specifically asking about ways to murder someone... with an ice cube!--Aspro (talk) 19:57, 1 October 2010 (UTC)[reply]

I have removed that tag. There is nothing wrong with the question. The reference desk seems to be getting more useless with each passsing day. He's only asking and we have no reason to believe he wants to kill anyone.--92.251.134.225 (talk) 20:23, 1 October 2010 (UTC)[reply]

Aw-shucks! I could just see it now:

An' I humbly submit to you... you, the ladies and gentlemen of the jury; is it not incontrovertible?! That-the -only-reason-that-the-accused -----standing-before-you-now------had-a-fridge, was that he intended... he planed... he pre---meditated, that the ice cubes that this this fridge would produce, would choke the very breath...the very breath out of a poor unfortunate... a poor unfortunate, who had never heard,.. nor come across,.. nor expected,.. that there existed,. such an evil expository, which consisted of all the things that should be shared freely and without restriction. That seemingly bottomless expository, which is known to it followers –they who hid behind a anonymous nom de plume's as yes!.. I speak of WIKEE... PEEDEEAH .--Aspro (talk) 20:50, 1 October 2010 (UTC) [reply]

2) Using a large piece of ice to inflict blunt force trauma

Reminds me of Lamb to the Slaughter. A tv series called Tales of the unexpected re-did it with Susan George (looking like butter would not melt in her mouth). They never did find the murder weapon --even though it was very delicious.--Aspro (talk) 19:57, 1 October 2010 (UTC)[reply]

In scenario 1, there would be a certain amount of water aspirated into the lungs as the victim struggled to breathe, and a significant quantity of water left in the body unless you figured out a way to dry the throat. There would also likely be signs of internal bruising from jamming in the ice and the bruising process would be halted at or near death so it could flag up as a proximate cause of death. They might not get you for using ice, but they could easily just claim you drowned the victim. Franamax (talk) 20:45, 1 October 2010 (UTC)[reply]

What about spiked ice cubes?Smallman12q (talk) 21:58, 1 October 2010 (UTC)[reply]

There's the old melting-ice-bullet trick, but it seems that one has been dealt with on "MythBusters". WikiDao ☯ (talk) 22:11, 1 October 2010 (UTC)[reply]

There's a common misconception about (the American) legal system that is perpetuated by Hollywood and television: absence of murder-weapon makes conviction impossible. This is not true at all: it is quite possible to convict somebody of murder, even if no weapon is found. Depending on circumstances, jurisdiction, and other evidence available, it's not even valid to say "it's more difficult to reach a conviction if the murder weapon isn't found." The legal system is complex, and though the trope of getting away with a crime because of a missing piece of evidence probably makes for good drama, it is an inaccurate rendition of the way an actual trial is conducted. For an introduction to this concept, see our article on evidence (law). In many cases, presence or absence of a murder weapon is circumstantial evidence and is very often irrelevant to both the ability of the prosecutor to bring specific charges or of the court to yield convictions for specific charges. On the other hand, in California, proof of the presence of a firearm at the scene means that additional charges can be brought - (in supplement to other charges, including homicide), merely because a weapon was present during the commission of a crime - even if the firearm had nothing to do with any crime taking place. Law is much more complicated than movies would have it seem. Nimur (talk) 21:15, 2 October 2010 (UTC)[reply]

I may not be an expert on law, but I would find it shocking if additional evidence such as a murder weapon would not make prosecution easier (assuming the prosecution was correct to begin with). Googlemeister (talk) 15:20, 4 October 2010 (UTC)[reply]

why do protons clump in the nucleus is they are all positively charged? Surely they would repel each other. I don't think this is taught at high school level...--92.251.134.225 (talk) 20:31, 1 October 2010 (UTC)[reply]

See Strong interaction (aka strong nuclear force). AndrewWTaylor (talk)

It's a super good question. The strong nuclear force basically makes nucleons (like protons) attract to each other. It's very powerful over short distances but weak once you start getting any distance in there at all. Understanding that the nucleus is always this balance of forces — strong nuclear vs. electromagnetic repulsion — makes things like nuclear fission make more sense, or the reason why you need neutrons. Neutrons don't have any effect on the electromagnetic forces, but do add strong force. So nuclei that would have too much positive electromagnetic repulsion become more stable when you add neutrons. Have too big of a nucleus (like uranium), and it starts to get unstable. Wobble that unstable nucleus a bit, and suddenly it is two very positively charged nuclei just outside the range of the strong nuclear force, which repel violently. (Most of the energy released by a fission reaction is in from this repulsion and is kinetic.) Nuclear fusion, by contrast, is hard to make work because you have to get two positively charged nuclei (repelling each other like mad) just close enough so that the strong nuclear force can kick in. --Mr.98 (talk) 20:44, 1 October 2010 (UTC)[reply]

Also see Nuclear force, but unfortunately these articles are not pitched at the elementary level. In fact, it is taught at high school level, in particular in elementary chemistry. Teenagers are taught that the isotopic mass of carbon-12 is arbitrarily assigned the number 12.000000. This is not surprising because a carbon-12 atom has 12 particles in its nucleus. But then they must learn that the isotopic mass of every other isotope is not equal to the number of particles in its nucleus. For example, the isotopic mass of oxygen-16 is not 16.000000 as one might expect — it is 15.9949146! The small amount of mass (0.0050854) that was lost when each oxygen-16 atom was assembled is related to the energy tied up in the strong interaction. The relationship between the lost mass and the energy tied up in keeping these repellant particles together is the familiar equation E = mc². Dolphin (t) 04:41, 2 October 2010 (UTC)[reply]

The wackyness of this is real. How do protons end up clustered together against tremendous repulsion? The answer is that everything we see and touch, except hydrogen, is the product of a supernova. It's said that we're star dust. The only way these nuclei exist is that they were forged together under the incredible pressures of a dying star. Wnt (talk) 00:30, 4 October 2010 (UTC)[reply]

"Weed is illegal because when it was made illegal, alcohol prohibition had just ended and the government couldn't just liquidate that whole agency that was working for prohibition, this was backed by the paper companies as hemp was set to replace paper. "

I read this somewhere. Is it true? ScienceApe (talk) 22:24, 1 October 2010 (UTC)[reply]

We have an article that discusses the history of the legality of cannabis. See also the 1937 Marihuana Tax Act article. WikiDao ☯ (talk) 22:51, 1 October 2010 (UTC)[reply]

Marijuana is illegal because it is an intoxicating substance. Period. Theres about a million conspiracy theories that some unrelated industry was trying to put the kibosh on hemp production, or some sort. The reality is, hemp isn't all that special of a fiber, and the cannibis plant is pretty much mostly useful as a source of wacky-tobacky. Those silly arguements are basically a redirection, let's convince people that legalizing hemp isn't about the drug, it's about a wonderfiber that will revolutionize the industry. If only the wood-pulp lobby would let it go through! It's like claiming that heroin is illegal because poppy-seed muffin bakers wanted to control their stock of poppy-seeds. Now, that doesn't say that I am arguing against legalization. Just that if you are going to argue, at least argue from a place of truth. --Jayron32 23:40, 1 October 2010 (UTC)[reply]

Uh... if you're going to make statements about arguing from a place of truth, it would behoove you to avoid such blanket statements that are directly contradicted by well-sourced statements here. Part of the reason is intoxication, part of the reason is hemp production. → ROUX ₪ 23:48, 1 October 2010 (UTC)[reply]

I'm not too familiar with the evil-paper-company theory, but the article seems well-sourced about some of it:

• NAFTA & neocolonialism: comparative criminal, human & social justice.
• Understanding marijuana: a new look at the scientific evidence
• Under the influence: the disinformation guide to drugs

Though clearly if it weren't so wacky it wouldn't be illegal, whatever other factors might also be driving that illegality. ;) WikiDao ☯ (talk) 23:54, 1 October 2010 (UTC)[reply]

One reason for keeping such drugs illegal is so that law'n'order oriented politicians have something to campaign on. Appeal to the masses by condemning those others. HiLo48 (talk) 23:58, 1 October 2010 (UTC)[reply]

As I've heard it, the primary reason MJ is still illegal is that three major industries - tobacco producers, alcohol producers, and insurance companies - put a lot of money into lobbying against it. the first two are worried about competition, the last about changes in insurance payouts. The tobacco industry is mixed on it: they've had long-term plans to begin producing and marketing MJ if it ever becomes fully legal (and could adapt a lot of their current growth, harvesting, storage, and packaging systems), but I think they are worried that MJ is too easy to grow and prepare, and that they won't be able to compete effectively with small-scale cottage industries. --Ludwigs2 04:37, 2 October 2010 (UTC)[reply]

You quotation included the government couldn't just liquidate that whole agency .... This is a classic pointer to the existence of a conspiracy theory. Dolphin (t) 04:48, 2 October 2010 (UTC)[reply]

I've grown convinced that the major factor must be that the gangs lobby the government to keep it illegal, just as they lobby certain officials to keep it effectively legal for them to sell. There are many billions of dollars at stake in the illegal market which will go away if the drug is legalized. Some of the edge effects that point this out:

• bans on "look alike substances" (to prevent people from selling fake pot and poisoning the open market)
• "trading up for the big fish" (to allow corrupt officials to choose which producers to prosecute, and especially to preserve the demand while tightening the supply)
• Mexico's recent hurry to legalize (to make sure the price differential across the border doesn't go away entirely if California passes proposition 19)
• deliberate neglect of any kind of drug treatment by the government (and in Mexico, open attacks on it by gangs).

I honestly think that if you took all the gang corruption out of drug laws, there'd literally be nothing left — they'd be legal almost immediately. If that seems counterintuitive, consider that nobody bans henbane and nobody sells it. It's like how patents and copyrights are supposed to encourage the dissemination of inventions by prohibiting it. Wnt (talk) 06:57, 2 October 2010 (UTC)[reply]

Why would anyone waste their time banning something that no one is selling? (Or in general, why waste time and money outlawing things that no one does?) APL (talk) 19:19, 2 October 2010 (UTC)[reply]

Indeed. And why would a street dealer waste his time selling what no one is banning? But history tells us that China's 1729 ban on opium was passed when it was an obscure drug, which was taken up only as a substitute after they banned tobacco in 1644. In a bit over a century the drug dealers were the conquerors. America will be no different. Wnt (talk) 00:21, 4 October 2010 (UTC)[reply]

I understand that its illegal because it induces psychosis. 92.28.254.154 (talk) 20:19, 2 October 2010 (UTC)[reply]

• Rather than enter this circular debate: here is a link to: After the War on Drugs: Blueprint for Regulation. Title says it all really.--Aspro (talk) 21:30, 2 October 2010 (UTC)[reply]

According to the United States Department of Justice, "Illegal drugs are illegal because they are harmful." Understandably, this website has a known bias (it is operated by the Drug Enforcement Agency), but it presents a very clear, easy-to-read explanation from an authoritative source that exactly answers the original question. People are free to speculate as much as they like about subterfuge and unseen motives behind government drug policy, but the real reasons behind drug legislation is actually pretty straightforward. The question of whether it is worthwhile or productive to enforce these policies is a different issue altogether. Nimur (talk) 18:04, 4 October 2010 (UTC)[reply]

I was just thinking that if this were possible, it might be easier to get hydrogen to undergo Nuclear Fusion. Is there any way to do it? ScienceApe (talk) 22:27, 1 October 2010 (UTC)[reply]

How do you propose to do so? By adjusting quantum physics? --The High Fin Sperm Whale 22:55, 1 October 2010 (UTC)[reply]

I was asking if it was possible. ScienceApe (talk) 23:04, 1 October 2010 (UTC)[reply]

At first glance, it doesn't seem outrageous. After all, you can focus the force carrier of electromagnetic radiation (i.e. with a lens), so if perchance there was some way to focus gluons in a similar manner. But alas, gluons travel only about a femtometer at the most, which is about the size of the atomic nucleus. There's simply no way to work with such a particle. --Jayron32 23:35, 1 October 2010 (UTC)[reply]

Well, there are nuclear isomers, which can have different properties. But if I look up "nuclear isomers of hydrogen" I get something unrelated (whether the nuclear and electron spins are aligned). I bet it's too simple to have any, but can someone knowledgeable confirm? Wnt (talk) 00:27, 4 October 2010 (UTC)[reply]

Here's hoping you all believe this is a genuine question! I've been housesitting and was kindly left money for some takeaways. Last night I ordered a pizza, ate some of it and put the rest in the fridge. On reheating a slice later in the microwave I opened the door to find a beetle (I think a Rove beetle) scurrying around :-( How did this critter survive when the pizza was piping hot? Could it simply have found a cool spot in the oven for 2.5 minutes? And does anybody know a good counsellor for my newly developed 'pizzaphobia' lol Spoonfulsofsheep (talk) 23:10, 1 October 2010 (UTC)[reply]

Had a similar experience a couple of years ago with small ants. Heated something in the microwave and found live ants in the oven when I open it. The Microwave article tells us that the actual wavelength of microwaves is typically in the range 1-10 cm, so if you're smaller than that, maybe the waves can't get you. HiLo48 (talk) 23:24, 1 October 2010 (UTC)[reply]

That's kind of a silly thing to say. You can microwave peas, for example, quite readily. → ROUX ₪ 23:44, 1 October 2010 (UTC)[reply]

Yep. OK. Next theory? HiLo48 (talk) 23:55, 1 October 2010 (UTC)[reply]

Thanks, I can see the sense in what you said. If the wavelength is large enough and the microwaves are focused at the central area of the oven (where the food would be) there could be 'safe' areas. No idea if you're right of course, and I'm not sticking my fingertip in an operating microwave to test your theory! Spoonfulsofsheep (talk) 00:13, 2 October 2010 (UTC)[reply]

From my recollections, HiLo48's original answer is basically correct. Due to the wavelengths of microwaves, there's something of a pattern of hot and cold areas in a microwave oven - and a small creature like an ant or a beetle can readily feel itself getting hot and move a few millimetres out of the hot spot - their comparatively large surface-area-to-volume ratio also allows them to shed unwanted heat very rapidly. A similarly small object like a pea will nonetheless be heated by a combination of (a) conduction and convection from its neighbors, (b) the spinning tray moving it into and out of hot-spots, and (c) its inability to move of its own accord. ~ mazca ^talk 00:58, 2 October 2010 (UTC)[reply]

Google Answers had a crack at explaining it here. HiLo48 is correct. So, to get rid of your bugs, what you need is for there to be a whole lot of them in there at the same time so you can microwave them as a group instead of hoping the waves will happen to hit the tiny individual. Matt Deres (talk) 01:16, 2 October 2010 (UTC)[reply]

Steve Baker liked to mention this sort of experiment [2] you can do with chocolate chips and by taking out the ring so the glass plate doesn't move which amongst other things shows the presence of 'hot' and 'cold' spots. Edit: I see the Google Answers actually suggests the same thing albeit with marshmallows Nil Einne (talk) 02:52, 2 October 2010 (UTC)[reply]

Might try putting one frozen pea in the microwave to see what happens. Clearly some research needed (and highly possible) here. HiLo48 (talk) 03:52, 2 October 2010 (UTC)[reply]

WP:OR per request I placed a ball of cheese 5 mm in diameter near the edge of a 32 cm diameter rotating plate in a 1650 W microwave oven. The cheese remained unaltered through about 270 degrees of plate-rotation, or about 11 seconds. Then it suddenly melted and sizzled at a mostly constant rate through 30 seconds. I repeated the experiment with an identical ball of cheese placed in the same start-position in the microwave, but this time the plate rotated in the opposite direction. After 90 degrees of rotation the second ball passed through the location where the first ball had melted, and then again continued up to about 270 degrees and 11 seconds before melting and sizzling as had the first. Conclusion: 5 mm seems sufficient for absorbing enough microwave radiation to cook food. WikiDao ☯ (talk) 06:16, 2 October 2010 (UTC)[reply]

I don't really understand why you let the plate rotate which seems to unnecessarily complicate any analysis Nil Einne (talk) 08:22, 2 October 2010 (UTC)[reply]

The plate rotates to more evenly heat food placed on it, because there are "cold spots" in a microwave oven. Presumably an insect could survive for a while if it remained in one of these poorly illuminated regions, but they tend to move around. I thought the experiment (with a "pea") was proposed to see if a bug-sized object might escape heating by virtue of its being too "tiny" for microwaves (1 mm to 1 m wavelength) to interact with it, but maybe I didn't understand it correctly. WikiDao ☯ (talk) 08:45, 2 October 2010 (UTC)[reply]

And reversing the rotation showed that it was not suddenly entering a "hot spot" that caused the cheese to cook, but average radiation intensity over time. So, any bugs surviving the amount of time it takes to heat a slice of pizza must have been hiding in a dark zone throughout that time -- unless it has to do with their water content. WikiDao ☯ (talk) 08:59, 2 October 2010 (UTC)[reply]

Well as the Google Answers said and is somewhat obvious, since bugs move around, they would likely move out of any hot spots, and if the plate is moving putting them in to hot spots they weren't in before they would likely move out of it quickly. Of course as Psychim as pointed out below, they may move off the plate anyway and it may not be just because they are trying to avoid the 'hot' spot they are feeling. And yes, you have it right about the plate, that's precisely why you stop it rotating when attempting to show the existanse of 'cold' spots and 'hot' spots but I think that wasn't what you were trying to show. (Actually I still don't understand what you were testing.) I would have thought it obvious that it takes a while for cheese to cook, but perhaps I'm not understanding something. Well I didn't really understand what the point of the pea experiment was for either. Nil Einne (talk) 10:18, 2 October 2010 (UTC)[reply]

I do think the existence of hot/cold regions is obvious. I thought it was about something like "absorption cross-section of a bug-sized object"! ;) WikiDao ☯ (talk) 11:14, 2 October 2010 (UTC)[reply]

Ah okay, I understand now. I'm not sure whether the ball of cheese is the best test subject though even if it's something easy to gauge. You could try some recently dead insects and see how long it takes them to cook. They will die before they cook of course. A perhaps better experiment would be if you have some sort of very quick temperature and resonably accurate for a small area temperature gauge. Quickly cut open the insect after it's been in the microwave and test the internal temperature. If it's more then say 50C I would say the insect would be dead if it were alive. Since microwave resonant heating works somewhat below the surface perhaps measuring the surface would work too. May be some sort of infrared thermometer? Do they work over such small areas? Nil Einne (talk) 16:59, 2 October 2010 (UTC)[reply]

Well an infrared thermometer is passively measuring infrared radiation emitted from the body. What would the difference be between the energy absorbed by the same 5 mm diameter object irradiated by microwaves with wavelength either 1 mm or 10 mm -- or even 100 mm? Any? WikiDao ☯ (talk) 19:28, 2 October 2010 (UTC)[reply]

Perhaps it is the water content (see Dielectric heating) of bugs that is "protecting" them from microwave heating relative to typical food material? WikiDao ☯ (talk) 06:29, 2 October 2010 (UTC)[reply]

Isn't it more likely that the food absorbs the microwaves and protects the insect? All the insects I've ever put in a microwave on their own have died quickly. Wnt (talk) 07:25, 2 October 2010 (UTC)[reply]

Well the more food there is in the microwave, the more microwaves are absorbed, so the lower the concentration in the "cold spots". Dbfirs 08:26, 3 October 2010 (UTC)[reply]

I'll go with the cold spot theory. The major cold spots in a microwave oven are along the edges and (especially) in corners, just the sort of place an insect would run too to try to escape. Physchim62 (talk) 09:24, 2 October 2010 (UTC)[reply]

And doesn't fall over? At the museum of natural history I once saw cylinders that show what rock would behave like at various depths and the more (man-made) heat and pressure endured the more they had to be glued afterwards to keep them together (for display) but after that it got "mooshed" with a crack and then "mooshed" with no cracks at all. So would pressure alone be strong enough and evenly distributed enough that it this would happen. (By tower I mean something skinnier than a mountain or plateau) What would happen to Earth's crust, by the way, since it is also rocks? If it's not strong or buoyant enough (due to the lack of a real mountain range's crustal "root"), would this be possible on a hypothetical infinitely strong surface? —Preceding unsigned comment added by 12.196.0.50 (talk) 23:38, 1 October 2010 (UTC)[reply]

Just imagine what would happen if you tried to build a tower out of Jello. It would goosh out laterally, right? This doesn't happen to the crust because it is so broad that it can't spread out. Looie496 (talk) 01:13, 2 October 2010 (UTC)[reply]

Rocks do behave like jello, but very very slowly. Solid rock will bend and flow, just on time scales on the order of millions of years. See Fold (geology). --Jayron32 01:48, 2 October 2010 (UTC)[reply]

No, I meant what would happen to the crust under a tower so tall it might flow plastically? Would it simply bend inwards like pushing down on a raft in a pool, would the preceeding happen and then tensile failure breaks it forming a microplate with the tower in the middle, or would the whole lot just fall into the mantle? Wouldn't this cause earthquakes?—Preceding unsigned comment added by 12.196.0.50 (talk • contribs)

I'm not sure such a tower could be built. Some natural structures which could approximate it may be something like Devils Tower National Monument, but I am unsure about what the rocks are like directly below the tower. Assuming you were just dealing with a very large, concentrated mass on the crust, it would depend on what kind of rock the crust under the tower is made of (sandstone is likely to react differently than basalt, for example), how heavy the tower is, on what time frames you are dealing with, etc. etc. Geology is far too complex, and there are far too many variables to just say "A big tower is on some rocks, and I want to know how it deforms them". --Jayron32 03:04, 2 October 2010 (UTC)[reply]

... and the time scale is very long! Here in the UK, the rocks are still rebounding from the effect of the ice sheets in the last ice age. Dbfirs 08:29, 2 October 2010 (UTC)[reply]

(ec) A series of very long term experiments have been carried out on granite beams in an effort to detect and quantify plastic deformation, see [3], the results indicate that granite has a viscosity of about 10 ²² poise. At that rate of deformation you would have to wait a long time (thousands of years) to see clear evidence of plastic deformation. Also your very large point load on the lithosphere would eventually (if large enough) cause an isostatic response as is seen in glacial loading. Finally, you would not be able to prevent a stone building failing by brittle fracture under its own weight if it was tall enough, even if the stone was literally 'flawless'. Mikenorton (talk) 08:44, 2 October 2010 (UTC)[reply]

Tower of Babel? ~AH1^(TCU) 15:37, 2 October 2010 (UTC)[reply]

Ha ha

You seem to be telling me cool rocks can't flow within a lifetime - ever, and that they would always break. If there's no way for it to break downwards then it would EXPLODE! Cool. —Preceding unsigned comment added by 12.196.0.50 (talk) 23:00, 2 October 2010 (UTC)[reply]

Hello all:

I was reading about the weak equivalence principle when it said that a spring force accelerometer would register no force when attached to an object that is in free fall, hence free fall and inertial motion are equivalent and that gravity really isn't a force, but just a space time distortion.

My question is that, suppose the following two scenarios:

We know that by the weak equivalence principle the bottom scenario of the two masses attracting each other through gravity, the accelerometer for mass A would register 0 N.

However, for the top scenario, if the iron weight moves sufficiently to magnet for the magnet's magnetic "action at distance" force to pull iron weight until it sticks to the magnet. How many Newtons of force would the accelerometer register for the iron weight during the process of the magnet pulling the iron weight to itself?

If the accelerometer registers 0 N then wouldn't that also show that the electromagnetic force isn't really a force but is equivalent to inertial motion (which we know to be false)? If the accelerometer registers a greater than 0 N force then would gravity be the only "force" out of the four fundamental forces of nature for which the accelerometer would register 0 N for "action at distance"?

Thanks.

L33th4x0r (talk) 23:43, 1 October 2010 (UTC)[reply]

Not sure I understand. It seems obvious that the accelerometer will register a force in this scenario. Looie496 (talk) 01:09, 2 October 2010 (UTC)[reply]

You might get weird results if the accelerometer's mechanisms were made of iron, of course. APL (talk) 01:29, 2 October 2010 (UTC)[reply]

The weak equivalence principle only applies to point particles in a gravitational field. Real objects which exist in three dimensions experience tidal forces, and so given infinitely accurate accelerometer, you would, for example, be able to deduce your orientation in free fall. See Equivalence_principle#The_weak_equivalence_principle. Also, once you introduce other forces besides gravity, all bets are off... --Jayron32 01:45, 2 October 2010 (UTC)[reply]

Yes! Gravity is the only force for wich the equivalence principle applies. 174.58.107.143 (talk) 05:31, 2 October 2010 (UTC)[reply]

The difference is that in the magnetic case the registered force depends on what the body is made of:You get a force if it is made of iron, you get no force if it is made of plastic, say. The gravitational case is different in that the result is completely independent of that. This is why the geometric interpretation works for gravity but not for electromagnetism. --Wrongfilter (talk) 07:57, 2 October 2010 (UTC)[reply]

thanks. L33th4x0r (talk) 15:48, 2 October 2010 (UTC)[reply]

The gravitational force between two masses is (clasically) inversely proportional to their distance apart. There will therefore be a difference between the attraction on the mass and on the more distant accelerometer towards the left mass. This difference will result in a small force on the spring. (and of course there is a force between the mass of the accelerometer and the right mass also) 71.31.152.112 (talk) 16:53, 3 October 2010 (UTC)[reply]

October 2

Plasma rocket to be tested in 2012 on space station would move space station76.28.54.105 (talk) 00:53, 2 October 2010 (UTC)[reply]

Is that a question or just a comment? Looie496 (talk) 01:07, 2 October 2010 (UTC)[reply]

Presumably you're referring to VASIMR. anonymous6494 01:39, 2 October 2010 (UTC)[reply]

YES it would move the station, the international space station could cruise around with VASIMR-like rockets, and that would be cool because they could explore the moon from orbit and then come back to an Earth orbit, thanks for pointing that out. The article referenced says it could be used for lunar cargo transport, or as a "space tug" and orbital transfer vehicle, the rockets I mean, but there is no reason I can think of why they can't use what is already there, the space station, for that for now. GabrielVelasquez (talk) 20:47, 2 October 2010 (UTC)[reply]

NO. The space station will not be leaving earth orbit with these or any other engines. It is too big and not built for lunar voyaging. It currently has something like 130 kW worth of solar panels but would need 8 mW (and somewhere to store 70 tons of argon propellant) Rmhermen (talk) 22:09, 2 October 2010 (UTC)[reply]

HOW MUCH COPPER IS THERE IN A HDMI CABLE? ALSO HOW MUCH GOLD? —Preceding unsigned comment added by Mole800 (talk • contribs) 00:56, 2 October 2010 (UTC)[reply]

Just a bit of friendly advice: Try to sign your posts, and DON'T USE CAPITALS, because people WILL THINK YOU ARE SHOUTING.--Editor510 ^{drop us a line, mate} 09:31, 2 October 2010 (UTC)[reply]

That depends on the length of the cable. However, I think that most cable have ab 2 mm plastic coating and the rest copper. --The High Fin Sperm Whale 01:39, 2 October 2010 (UTC)[reply]

(edit conflict) It depends on the brand of cable, its length, etc. etc. Its impossible to make a general statement about the composition without knowing exactly which cable. Also, please do not type in all caps. In all internet forums, all caps is read as SHOUTING and is impolite. --Jayron32 01:41, 2 October 2010 (UTC)[reply]

Just weigh your cable, and probably about 90% of the weight is copper. The amount of gold is just a few micrograms to plate the contacts for the (partially) justifiable reason that bad contacts can cause a deterioration in the signal. Dbfirs 08:22, 2 October 2010 (UTC)[reply]

I'm not sure that that's true — for smaller-gauge wire, the layer of insulation around it is going to make up a proportionally-larger fraction of the total weight. (I agree completely with you about the utterly negligible amount of gold in the product.) I've seen HDMI cables marketed that are manufactured using anywhere from 22 gauge (quite heavy) to 28 gauge (lightweight) conductors. Nineteen 28 gauge wires will contain only about fourteen grams of copper per meter; rendered in 22 gauge cable you're looking at more then four times that mass. TenOfAllTrades(talk) 14:56, 2 October 2010 (UTC)[reply]

You make a valid point, and my estimate was only an approximation, but thicker cable tends to have a better insulation, and plastic is very light compared with copper, so I still claim that weighing the cable is the best way to estimate the weight of copper. Obviously 22 gauge will weigh about four times as much as 28 gauge, but that doesn't seriously upset the percentage, and have you ever seen nineteen strands of 22 gauge wire? Dbfirs 15:49, 2 October 2010 (UTC)[reply]

What are the best indoor air cleaners to remove pollution from motor vehicle exhaust? Many thanks! --3kdocnmjduif (talk) 01:49, 2 October 2010 (UTC)[reply]

HEPA filters will remove particulate. Catalytic converters minimize the release of nitrogen oxides, carbon monoxide, and unburnt gasoline. --Jayron32 01:55, 2 October 2010 (UTC)[reply]

It is the Clean Air Delivery Rate you need to use to compare devices with. Good units use a HEPTA filter, a carbon filter, and an ionizer. Just one on its own is no good for traffic pollution. Catalytic converters are not practical for indoor use.--Aspro (talk) 09:00, 2 October 2010 (UTC)[reply]

Here is an example of one that is suitable for a room up to 15m². [4] I bought a similar one for someone who stuffer from hay fever and pollution in general and he was amazed by how much better he could breath. I find its like walking into a room that is on a mountain top but then, after a time you gt use to it and its just every body else's house that smells like a dusty back yard of a fast-food-take-away situated under some flyover. --Aspro (talk) 09:39, 2 October 2010 (UTC)[reply]

I've heard some bad stuff about air ionizers - that people should avoid them... thoughts? I'm thinking of maybe installing a central air filter (in the ventilation system) - is that a good idea? --3kdocnmjduif (talk) 12:52, 2 October 2010 (UTC)[reply]

Don't forget to read indoor air quality and vehicle exhaust. ~AH1^(TCU) 15:35, 2 October 2010 (UTC)[reply]

whats Softwood plywood —Preceding unsigned comment added by Kj650 (talk • contribs) 04:22, 2 October 2010 (UTC)[reply]

Do the articles Softwood and Plywood answer your question? --Jayron32 04:24, 2 October 2010 (UTC)[reply]

no —Preceding unsigned comment added by Kj650 (talk • contribs) 06:59, 2 October 2010 (UTC)[reply]

Softwood plywood is usually made either of Douglas fir or spruce, pine and fir (collectively known as spruce-pine-fir or SPF), and is typically used for construction and industrial purposes. Richard Avery (talk) 07:22, 2 October 2010 (UTC)[reply]

It is also cheap and so is usefully for formwork were it will be discarded afterwords or for use were it wont be seen -in other words, it lacks long term durability and it usually has a poor outward finish.--Aspro (talk) 09:13, 2 October 2010 (UTC)[reply]

what is the calorific value of human breast milk? —Preceding unsigned comment added by 218.248.64.167 (talk) 07:15, 2 October 2010 (UTC)[reply]

They say it's 70 calories per 100 ml. This article on what to eat when breastfeeding also has interesting numbers. Our article on breast milk gives no numbers, sadly. Happy? Cheers, Ouro (blah blah) 08:04, 2 October 2010 (UTC)[reply]

This is NOT a medical question, it's not serious, I was just wondering, why does my head click if I turn it too fast? It feels like two sections of my skull sliding over each other. Is it my spine? Just puzzled, that's all.--Editor510 ^{drop us a line, mate} 09:29, 2 October 2010 (UTC)[reply]

We have an article on Neck creaking; it could be that. WikiDao ☯ (talk) 09:34, 2 October 2010 (UTC)[reply]

No, I can actually feel it, it's not a sound, and it shoots right through the back of my head, near the cranium.--Editor510 ^{drop us a line, mate} 10:36, 2 October 2010 (UTC)[reply]

The link within that article to Cracking joints is what you want. If it's not, then see a doctor. Vimescarrot (talk) 10:38, 2 October 2010 (UTC)[reply]

It's nothing serious, I think it's just to do with nerves.--Editor510 ^{drop us a line, mate} 07:18, 3 October 2010 (UTC)[reply]

I recently read up on globus pharyngis as it sounds remotely similar to your condition, but this is not an attempt to diagnose, and if you actually have that condition then you should consult a doctor. ~AH1^(TCU) 15:34, 2 October 2010 (UTC)[reply]

No, I think it's just something to do with the spine and skull, perhaps due to stiffness. Definitely nothing deadly or dangerous. Thank you anyway.--Editor510 ^{drop us a line, mate} 07:41, 3 October 2010 (UTC)[reply]

Resolved

i have a speaker with writings

                   50F/500
                     16 ohm

i understand that 16 ohm is the resistance of the speaker. but what is this "50F/500" .

one more thing -- if i want to produce a high frequency sound through a speaker, had it to meet some conditions. is so please specify what Thanx--Myownid420 (talk) 09:43, 2 October 2010 (UTC)[reply]

You may want to take a read of Loudspeaker. In particular, it is almost definitely the case that 16 ohm is the Electrical impedance not simply the 'resistance' of the speaker. Nil Einne (talk) 10:05, 2 October 2010 (UTC)[reply]

You don't specify how high a frequency you wish to produce, but you might like to read about tweeters. Dbfirs 15:42, 2 October 2010 (UTC)[reply]

What is it called when two flavors together seem to enhance eachother or cancel eachother out, and how does this happen? In other words, we can break down the sense of taste into a variety of different receptors, but a flavor is more than just a combination of sweet, salty, sour, bitter, and umami, right? 96.255.178.76 (talk) 16:03, 2 October 2010 (UTC)[reply]

well, it's not simply a matter of taste. for instance, I know that an old chef's trick is to use salt and garlic together, because the salt overwhelms the taste buds in the mouth and so enhances the aroma of the garlic. scent is a more subtle sense, capable of distinguishing far more nuances than the simple five tastes, and so you can't discount the interaction between them. --Ludwigs2 17:11, 2 October 2010 (UTC)[reply]

We don't really perceive those basic tastes separately, though. Kind of if you take a red light and add green light to it you get yellow light. Yellow doesn't look red at all.

(We've only got 'three basic colors, but that doesn't stop us from seeing roughly a zillion colors.) APL (talk) 20:30, 2 October 2010 (UTC)[reply]

Not quite the same. Taste is synergistic, and chemically so. MSG + garlic + cilantro ==> a very synergistic mix. Sweet inhibits bitter. John Riemann Soong (talk) 08:35, 3 October 2010 (UTC)[reply]

can we create electrical energy by applying electromagnetic induction in planes?? —Preceding unsigned comment added by 117.194.64.85 (talk) 16:14, 2 October 2010 (UTC)[reply]

I added a title to this question to separate it from the previous section. Vimescarrot (talk) 16:59, 2 October 2010 (UTC)[reply]

Assuming you mean airplanes rather than geometric planes, we can certainly transform energy, like from air flow to electrical power by a little aux power generator driven by airflow or by rotation of the engine to electricity from a generator. Perhaps some form of waste energy could be changed into electricity by electromagnetic induction. A transformer in an airplane also changes one voltage and current level to another. I do not think that any energy will be "created" from nothing just by some electromagnetic doodad being placed on an airplane. For instance, if a coil of wire on an airplane cut through the Earth's magnetic field, a voltage and current could be produced in the coil, but there would be a mechanical force slowing down the plane a bit as a result. Edison (talk) 19:19, 2 October 2010 (UTC)[reply]

Are there any deadly poisonous mushrooms in British Columbia, especially in the Lower Mainland? And this is not a medical question, and I am not about to eat a mushroom. --The High Fin Sperm Whale 18:10, 2 October 2010 (UTC)[reply]

You are likely to find both amanita muscaria and amanita pantherina, according to this - no doubt there are others. Mikenorton (talk) 19:12, 2 October 2010 (UTC)[reply]

Thanks, I have seen Fly agarics, but is there anything that one bite of it can be deadly? --The High Fin Sperm Whale 19:18, 2 October 2010 (UTC)[reply]

I don't know about one bite but the death cap, amanita phalloides, has caused at least one fatality in BC [5] and that only needs half a mushroom. Mikenorton (talk) 19:40, 2 October 2010 (UTC)[reply]

One bite of that could kill you (or make you wish you were dead). Easy to stupidly do accidentally, and easy to add to a murder mystery plot. --jpgordon^{::==( o )} 20:27, 2 October 2010 (UTC)[reply]

Before, I thought I shouldn't eat mushrooms I find. Now, I know not to eat mushrooms I find. Thanks guys! --The High Fin Sperm Whale 20:58, 2 October 2010 (UTC)[reply]

Destroying angels probably occur in the Lower Mainland. Pfly (talk) 22:34, 2 October 2010 (UTC)[reply]

How many "waters of crystalization" are there in crystaline sucrose71.2.132.222 (talk) 19:30, 2 October 2010 (UTC)[reply]

I don't think that there is any water of crystallization. In case you didn't know, water of crystallization is water molecules that are attached to the crystal structure of the molecule. Have a nice one, --Chemicalinterest (talk) 20:36, 2 October 2010 (UTC)[reply]

What's the name of that place in the US where they keep lots and lots of different types of diseases? There are three or four levels, with increasing levels of security, depending on how dangerous they are. — Fly by Night (talk) 20:11, 2 October 2010 (UTC)[reply]

Centers for Disease Control and Prevention? Mikenorton (talk) 20:16, 2 October 2010 (UTC)[reply]

Biosafety level is all about the various levels and a listing of the few places that have the highest-level facilities. Careful to distinguish "level" (amount) of safety from "level" (floor) of a building (question seems to mix the two...unclear if there is really a single repository of all major pathogens). DMacks (talk) 20:21, 2 October 2010 (UTC)[reply]

There are multiple ones around the U.S. The most obvious ones are the CDC in Atlanta and USAMRIID in Maryland. Shadowjams (talk) 20:37, 2 October 2010 (UTC)[reply]

Wikipedia list of Level 3 and 4 facilities. Shadowjams (talk) 20:41, 2 October 2010 (UTC)[reply]

[[Maybe Plum Island? Rmhermen (talk) 21:01, 2 October 2010 (UTC)[reply]

from what I hear, Plum Island has been deactivated as a disease research location. --Ludwigs2 03:37, 3 October 2010 (UTC) [reply]

I remeber seeing somewhere that cats and dogs don't see TV the same as we do, which is shame because they could learn so much and we could even help them evolve that way, but isn't there some way TVs could be adapted for dogs and cats, even something like a D&C-3D technology. Not to sound like a prophet but I bet plenty of people would subscribe to that channel for their pets. The African Grey can learn nearly a thousand word vocabulary, and I'm sure a 3D verson of some kids learning show would go a long way to educate them. Yes I just said educate a bird, not a bachelors degree or anything like that but, elementary school graduate maybe. GabrielVelasquez (talk) 20:51, 2 October 2010 (UTC)[reply]
Okay not quite a thousand, this article says "950." GabrielVelasquez (talk) 21:02, 2 October 2010 (UTC)[reply]
"They have the capacity to have a vocabulary of over 2000 words." - GabrielVelasquez (talk) 21:05, 2 October 2010 (UTC)[reply]
...isn't there some way TVs could be adapted for dogs and cats? GabrielVelasquez (talk) 23:02, 2 October 2010 (UTC)[reply]

See animal language. The level of abstraction displayed by even a kindergardener's language usage is probably utterly unobtainable by any other animal. I remember reading somewhere the insightful comment that the difference between having a specific signal for "watch out: there's a snake" and being able to talk about snakes ("thank goodness there's no snake here", or "remember that snake?", or "do you suppose snakes are as dangerous as tigers?") is huge. Human language and learning are both all about abstraction. The African Grey parrot is really smart as animals go, but language is not just about accumulating a bunch of definitions. Paul (Stansifer) 04:39, 3 October 2010 (UTC)[reply]

I wonder who is Albert Einstein's notable student? —Preceding unsigned comment added by 174.20.65.111 (talk) 20:59, 2 October 2010 (UTC)[reply]

Give up! Who is he?--Aspro (talk) 21:37, 2 October 2010 (UTC)[reply]

I don't know? That's why i'm asking. ANYONE knows? Albert Einstein doesn't have any student?174.20.65.111 (talk) 21:48, 2 October 2010 (UTC)[reply]

Perhaps Leó Szilárd - I'm not sure that Einstein had many students in the normal understanding of the term. Mikenorton (talk) 21:55, 2 October 2010 (UTC)[reply]

My understanding is that somatic cells accumulate many mutations over our lifetime, contributing to ageing. If this is the case, then shouldn't germ cells also accumulate the same mutations? They're not more protected from chemical and electromagnetic mutagens than any other cells, surely? Are there special restorative process active in these cells that aren't active in somatic cells? If the germ cells accumulated mutations at the same rate as somatic cells, successive generations would be expected to leave begin increasingly aged offspring. I don't get it. --178.98.65.241 (talk) 21:34, 2 October 2010 (UTC)[reply]

I'm not sure so I'll speculate, and anyone else can feel free to shoot down the idea. Whilst meitotic cells aren't any more protected against damage than mitotic cells, wouldn't the fitter, less damaged cells be more likely to reach the ovum than damaged ones? In any case, sperm are constantly made in the testes, so it's not like these cells have to cope with prolonged exposure to radiation or chemicals. Also, 'aged' cells are damaged physically but often the DNA may remain mostly in it's original form. As long as the genes for mechanisms of DNA repair remain unaffected and crucial genes of function aren't damaged, why would aging accumulate in successive generations? Regards, --—Cyclonenim | Chat  21:40, 2 October 2010 (UTC)[reply]

Aging is a little more complicated than somatic cells acquiring mutations. That is probably part of it, but there are also a number of other biological components, including telomere shortening and senescence of somatic stem cells. The fact is that new mutations happen in EVERY germ cell -- we all have a thousands of new mutations (see mutation rate). Of course, most of those mutations have absolutely no repercussions, but every so often a mutation happens in a critical gene and causes a disorder. That being said, see paternal age effect for discussion of fertility, pregnancy/birth complications, and some medical conditions associated with advanced paternal age. --- Medical geneticist (talk) 22:46, 2 October 2010 (UTC)[reply]

We don't seem to have an article on germ-cell segregation, which happens in the embryo and means that the cells that go on to produce your offspring will reproduce themselves far less regularly than the cells that keep your body alive. Physchim62 (talk) 23:21, 2 October 2010 (UTC)[reply]

I agree with Medical geneticist, and would add another consideration: the accumulation of mutations in the germ line is called "evolution". Sure, some will be deleterious, and if sufficiently so may affect reproduction (and thus will be lost by the population). Others will contribute to population diversification, which provides distinct individuals that will have various levels of fitness under various selective forces. -- Scray (talk) 03:49, 3 October 2010 (UTC)[reply]

See [6] for a discussion of age and mutation rate. Bear in mind that sperm has its own private, very strong process of natural selection on the way to the egg, which probably weeds out a good variety of harmful mutations (and probably misses quite a few as well). The way to weed out the mutations that get through, ultimately, is by death and the natural selection of new offspring; which suggests that if humanity succeeds in extending its lifespan, eventually nature will push back indeed by mutating the offspring beyond the capacity of natural selection to remove. Of course, natural selection has already been taking some time off of late, which should create the same type of pressure anyway. But if you learn all the SNPs in the human genome, and can recognize any new mutation, and can fix it, all that becomes moot. Wnt (talk) 00:14, 4 October 2010 (UTC)[reply]

After reading the article Black hole, I'm still a little mystified. Are there any actual confirmed black holes, or are they all candidates? If the latter is true, then I'm guessing List of black hole candidates and List of black holes need to be merged... --- cymru lass ^{(hit me up)}⁄_{(background check)} 21:44, 2 October 2010 (UTC)[reply]

There are confirmed candidates, i.e. matching the criteria we assume to relate to a black hole (see here. I'm not a physicist, so I can't explain why this evidence doesn't prove they exist 100%, but apparently it doesn't. I'll let someone else cover that. With respect to merging, probably still a good idea. Regards, --—Cyclonenim | Chat  22:24, 2 October 2010 (UTC)[reply]

Okie doke. Thanks!

"...why the evidence doesn't prove why they exist 100%..." Science requires that when additional (valid) data contradicts a theory (rather a theory's predictions) that the theory be abandoned or modified (or reinterpreted). In Science, unlike religion, there can be no 100% proof, by definition (at least until all possible experiments have been done).

There are several reasons why we can not confirm the existence of black holes. We can not directly observe them (they give off no radiation). (a claim was made in September 2010 that Hawking Radiation has been observed - but HR is black body radiation and is characteristic of any mass at a specific temperature and not exclusive to bhs). They are invariably obscured by a halo of surrounding (orbiting) material and material in between us and the central object. At astronomical distances their observed effects are principally due to gravity, again not unique to bhs. Finally, there are significant inadequacies in applying general relativity to quantum physics and the collapse of matter/space into a bh is inherently quantum in nature. While they are the most likely explanation for our observations, until we have developed a better theoretical framework that can explain the progression from normal matter to bh singularities (for instance states of matter consisting of degenerate neutrons or quarks are posited to exist but are not well understood - see Strange matter in wikipedia) we should not be mataphysically certain that what we are "observing" is fully collapsed space-time. (although many scientists are sure it does exist and we are observing it, more conservative scientists will only admit that what we observed is consistent with what (little) we understand about bhs and quantum relativity)71.31.152.112 (talk) 18:08, 3 October 2010 (UTC)[reply]

I edited your comment, 71.31.152.112 to make it visible. Putting a space in front of a comment turns it into a boxed comment. --Chemicalinterest (talk) 18:24, 3 October 2010 (UTC)[reply]

Hello, I recently went on a mushroom hunting expedition and found several mushrooms that I don't know the names of. Can someone please help me identify them? Thanks, --The High Fin Sperm Whale 22:20, 2 October 2010 (UTC)[reply]

• 
  1. Possibly Macrolepiota procera
• 
  1. Same from side
• 
  1. Same from top
• 
  2.
• 
  3.

Number 2 is Geastraceae, also known as an earthstar mushroom. Looie496 (talk) 23:08, 2 October 2010 (UTC)[reply]

Geastrum saccatum perhaps? --The High Fin Sperm Whale 23:45, 2 October 2010 (UTC)[reply]

And I think that the first three are Lepiota rachodes. --The High Fin Sperm Whale 00:48, 3 October 2010 (UTC)[reply]

We just had a featured article on an earthstar, so now I recognize #2 as something from Geastraceae. But I won't pretend to know which. Wnt (talk) 17:10, 5 October 2010 (UTC)[reply]

Just reading Baden-Powell's report on the Siege of Mafeking, and in it he refers to devices called phonophores. They are in his Communications section, under the sub-heading of Signalling. The sentence reads in full "Phonophores were also made and used on the armoured train, attached to ordinary telephone lines". Now, Chambers 20th Century Dictionary, 1983 edition, page 962, says of phonophore "a sound-conducting apparatus, of various kinds: a device for telephoning and telegraphing simultaneously by the same wire". Which is all very well, but does anyone know anything more about them (how they work etc), or even better about the ones B-P had made? DuncanHill (talk) 22:56, 2 October 2010 (UTC)[reply]

Assuming this is the communication device on railway trains, it looks like one of those very old telephones - a wooden box with a ceramic funnel for talking into and listening. I have seen them on tours of old trains, but they weren't called "phonophores". They were called "phones". Perhaps phonophore is the proper name for them. They were needed for immediate communication between the caboose and the engine. -- kainaw™ 23:18, 2 October 2010 (UTC)[reply]

(ec) Also known as a 'condenser telephone' apparently, which was invented by Edison, and so perhaps this is just a portable telephone apparatus attached to a telegraph line to allow voice communication, see [7]? Mikenorton (talk) 23:21, 2 October 2010 (UTC)[reply]

Thanks, the portable apparatus sounds likely in the context. DuncanHill (talk) 23:39, 2 October 2010 (UTC)[reply]

The first edition of the Oxford English Dictionary gives this definition for "phonopore": "Name of an apparatus by means of which electrical impulses produced by induction, as in a telephone, may be used to transmit messages along a telegraph wire, without interfering with the current by which ordinary messages are transmitted."

I don't know how they made them, but the physical principle is quite simple: telegraph messages were sent in Morse code, that is at a rate of no more than a few hertz; speech signals, which have a higher frequency, can be sent along the same line without interference, and the electronic circuitry to sort out one message from the other is very simple, high-school level in most countries. Physchim62 (talk) 00:14, 3 October 2010 (UTC)[reply]

Do you have an exact reference to Baden-Powell's discussion of phonophore? Why did he need to signal between two nearby telegraph systems lacking a direct connection? [8] indicates a "phonohore" was similar to Thomas Edison's "grasshopper" earlier telegraph of the 1880's which used a high frequency inductively (or capacitively) coupled signal to connect a transmitting circuit to a receiving circuit without a direct metallic connection, in other words, wireless telegraphy. The regular telegraph was pure DC. The phonophore in the reference, invented by Mr. C. Langdon-Davies of London, was a tuned high frequency (though perhaps audible and lower than radio frequency) AC telegraph transmission. It could transmit speech [9] like the pre-radio system of Nathan Stubblefield, but such a usage would have to remove the tuned transmit and receive frequencies and use simple baseband audio. Short range and inefficient compared to radio. Edison (talk) 00:28, 4 October 2010 (UTC)[reply]

I found [10]]. Why were the opponents of Powell too lazy to cut the telegraph wires at multiple points, so that his wireless inductive/capacitive connection to them would have been rendered useless? Why was he too lazy to stop and connect a telegraph key to the telegraph line? How could he travel about in an "armored train" when ten minutes work would have made the tracks unusable?Why didn't the opponents just pull a couple of spikes and disconnect the rails? Was everyone in that war daft? A great mystery. Edison (talk) 00:39, 4 October 2010 (UTC)[reply]

It wasn't a siege in the sense of a castle surrounded on all sides by the enemy. The force available to the Boers wasn't sufficient to completely invest the town, and B-P had mobile forces both in the town and to the north able to sally forth and engage with any Boers who had left their prepared positions. I don't think he was "too lazy to stop and connect a telegraph key" (lazy is one word you'll never hear directed at B-P), if a phonophore gave him a ready voice link to the soldiers on the armoured train he'd have leapt at the idea. DuncanHill (talk) 09:21, 4 October 2010 (UTC)[reply]

The sentence I quoted is from the Report of the Siege of Mafeking, by Major-General Baden-Powell, October 1899 - May 1900, submitted to Lord Roberts (Commanding-in-Chief), and reprinted in The Siege Collection, Uncovered Editions, The Stationery Office, London, 2001, ISBN 0117024643. It appears on page 241 of this edition. DuncanHill (talk) 09:31, 4 October 2010 (UTC)[reply]

Re Edison's question about the vulnerablity of Armoured trains; they were much used in the Second Boer War[11], where the only way to cover the huge distances involved was on horseback or by rail. Apparently it is not easy for a man on a horse to destroy a rail track. They were invented in the American Civil War and last used in World War II[12][13]. We Brits had a very small armoured train that ran on the Romney, Hythe and Dymchurch Railway in 1940[14]. Alansplodge (talk) 18:52, 4 October 2010 (UTC)[reply]

A simple Google search gives "Phonophore (jō'nó-fōr), is a device of Langdon Davies of London, England, for transmitting electric signals through circuits which are not closed. Messages have been sent over wires open at both ends, in circumstances which would render ordinary telegraphing impossible. The same wire has been used at once for ordinary telegraphing and for the transmission of phonophore signals. When, the resistance having been greatly increased, the ordinary signals ceased, those of the phonophore continued as distinct as before. The transmitter is fitted with a vibrating reed at one end and the receiver with a stretched steel band at the other, which can be tuned to the same note." http://chestofbooks.com/reference/The-New-Student-s-Reference-Work-Vol3/pp0371.html

If one length of telegraph wire were cut, at each end of a section, no signal could have propagated beyond the cut section. It was not magic. It was just an audio signal coupled to a telegraph circuit. A party of men on horseback carrying very basic tools like prybars could have pulled the spikes and lifted a section of rail in 10 minutes, as evidenced from the American Civil War or 150 years of railroad history, or from my personal experience working on a railroad. If they had any explosives, it would have been far quicker to prevent the travel of the "armored train." The whole history makes no sense. Did the Boers and the British lack the ability to climb telegraph poles? Did the Boers lack the physical strength to pull a few spikes or to chop down telegraph poles and cut wires? Did their commanders lack knowledge of how railroads and telegraphy worked? Edison (talk) 02:06, 5 October 2010 (UTC)[reply]

You see the enemy riding out towards your telegraph or railway line and so you send someone out to intercept or harass them. Someone pulls out a spike? You hammer it back in. Neither side at Mafeking had great numbers of men, the lines were permeable, both had spies amongst the native population, and the country provided little cover. Do read the report if you get the chance, it's fascinating stuff. DuncanHill (talk) 00:34, 7 October 2010 (UTC)[reply]

A little more searching found http://www.angloboerwar.com/other-information/16-other-information/1859-railways which gives a picture of an armoured train and says "Armoured trains were officially recognised as moving telegraph offices, and equipped with field sounders, vibrators, phonophores and telephones; and whenever trains stopped away from a regular office, which they did nearly every night, they were never out of communication with the neighbouring stations and blockhouses. When several trains patrolled one section, it was found advisable especially at night, that they should all halt at fixed intervals and connect up with the telegraph wires to receive instructions and news."

This Google search finds seven enteries for Langdon Davies' phonophone: http://www.google.co.uk/search?hl=en&safe=off&biw=1016&bih=572&q=phonophores+%22langdon+davies%22&aq=f&aqi=&aql=&oq=&gs_rfai= Where do I send my bill? 92.29.114.118 (talk) 20:50, 4 October 2010 (UTC)[reply]

Many thanks, unfortunately we are not allowed to let anyone know where Wikipedia is based, so you won't be able to send a bill. DuncanHill (talk) 23:46, 4 October 2010 (UTC)[reply]

October 3

Does the center of mass of the Earth change its position with respect to the plane of the equator and its axis. —Preceding unsigned comment added by 113.199.208.88 (talk) 08:51, 3 October 2010 (UTC)[reply]

Yes. According to this site, "The Earth's centre of gravity constantly changes position within a three-centimetre cube in response to mass redistributions on the surface of the globe, caused by shifting masses within the ocean and by soil moisture, snow cover and groundwater."

I would also have expected some movement due to convection currents in the liquid portions of the mantle and core (see Structure of the Earth) moving around material of slightly different densities, but I haven't found a specific reference for that (yet). 87.81.230.195 (talk) 12:36, 3 October 2010 (UTC)[reply]

And what is this amazing centre of gravity constraining three-centimetre cube is made out of? Nickel-iron alloy, presumably. -- 111.84.196.147 (talk) 13:17, 3 October 2010 (UTC)[reply]

As I'm sure you know, the '3cm cube' is just a visualization trick. in fact, the actual center of gravity of the Earth is probably only definable in terms of a 3-dimensional confidence interval, which probably has a shape (at any given confidence level) like a flattened sphere or fat disk (on the assumption that most of the variation is in the equatorial plane, and less is in the axial plane) --Ludwigs2 19:56, 3 October 2010 (UTC)[reply]

We have an article on polar motion which seems to be what you're looking for. There is also an effect called nutation, which is due to the moon. Physchim62 (talk) 00:40, 4 October 2010 (UTC)[reply]

What about the tides from the moon? Do they cause any changes to radial velocity relative to the Sun, within the Earth-moon gravitational centre system? ~AH1^(TCU) 14:34, 3 October 2010 (UTC)[reply]

The answer to the original question is no. Both the equator and the axis of rotation pass through the center of mass by definition. If the center of mass moves (in relation to something else, like the surface of a large part of the Earth), then the equator and/or the axis of rotation move with it. --Anonymous, 06:35 UTC, October 4, 2010.

The post just above by anonymous would apply if the Earth was a prefect sphere. However, in reality (as one is taught in school geography lessons) it is a slightly pear shaped oblate spheroid giving ellipsoid that is triaxial . Thus the 'geometric' and 'centre of mass' is not necessarily going to coincide. Satellite ranging has already shown that for Mars, the centre of mass and the geometric centres do not coincided exactly either. The World Geodetic System 84 gets round this problem by ascertaining the centre of gravity (mass) and generating a perfect theoretical gravimetric ellipsoid as a datum from which all other spheres can be compared.--Aspro (talk) 08:47, 4 October 2010 (UTC)[reply]

No, I was talking about the real world, not a perfect sphere, and the center of mass, not any sort of geometric center. --Anonymous, 16:02 UTC, October 4, 2010.

The OP has said nothing about ignoring the cartographers equator and axis and geometric shape, and so as it stands it is a reasonable question. If he was taking about your interpretation of equator and axis there would be no point in asking it. He is asking about the 'real' world which is the point of his question. Your second post also contradicts your first. To my mind some people do ask pointless questions here but you appear to be prejudging either his motives or his intelligence, either which is in my view despicable.--Aspro (talk) 18:44, 4 October 2010 (UTC)[reply]

The question specificially defined what it was asking about -- the equator and axis in relation to the center of gravity. I answered in those terms after other people answered in other ways. I don't see how it can be construed as inappropriately judgemental to answer the question that was asked, but I'll just say that I was not intending to malign anyone. --Anonymous, 03:17 UTC, October 5, 2010.

I have a map of the galaxy as seen from what I will, for want of a better term, call above. However, this uses a system of coordinates based on angles from a line passing from the earth to the centre of the galaxy, rather different to that used to determine where stars are from earth. How, then, would I go about plotting the location of a particular star on this map using the coordinates given for its location within the sky?

148.197.121.205 (talk) 12:10, 3 October 2010 (UTC)[reply]

Does celestial coordinate system help? --81.153.109.200 (talk) 12:16, 3 October 2010 (UTC)[reply]

(EC) The article Celestial coordinate system has links to more detailed descriptions of these two systems - the Galactic and the Equatorial systems - (as well as other), and a section explaining how to convert between the Equatorial and Horizontal systems, but not explicitly the conversion you need. However you may be able to use the correct terminologies in these articles to help search for the appropriate conversion, which I'm sure is out there.

[Addendum] Doh! See the first external link in the Galactic coordinate system article! 87.81.230.195 (talk) 12:21, 3 October 2010 (UTC)[reply]

Does bio engineering have good, strong prospects in the future? I know bio engineering is a broad field, but I have applied for undergraduates at the moment so a rough explanation would suffice. And also microbiology. Thanks.--119.155.118.204 (talk) 15:29, 3 October 2010 (UTC)[reply]

The article biological engineering explains the wide and robust areas of research. Is there a specific topic you wanted information about? -- kainaw™ 16:02, 3 October 2010 (UTC)[reply]

The prospects for both fields are excellent -- bioengineering in particular is bound to grow vastly in the next couple of decades. The prospects for an individual going into a field also depend on the amount of competition, though, and I don't know anything about that. Looie496 (talk) 16:22, 3 October 2010 (UTC)[reply]

Also take a look at biochemical engineering and biogeochemistry. ~AH1^(TCU) 18:17, 3 October 2010 (UTC)[reply]

And biomedical engineering. Regards, --—Cyclonenim | Chat  21:06, 3 October 2010 (UTC)[reply]

In the article on the Chinese Chang'e 1 lunar probe, there's a picture of the rocket carrying the probe blasting off. The rocket seems to have only one engine and no fins. How does the rocket adjust its direction of travel? —Preceding unsigned comment added by 96.227.60.253 (talk) 16:24, 3 October 2010 (UTC)[reply]

See gimbal#Rocket engines -- Finlay McWalter ☻ Talk 16:40, 3 October 2010 (UTC)[reply]

This page has some nice diagrams and animations illustrating the principle. I guess because they are NASA we could import them to Wikipedia? --Mr.98 (talk) 16:43, 3 October 2010 (UTC)[reply]

Once launched, spacecraft use a reaction control system to manoeuvre. For some operations, like moving from a Lunar orbit into a return-to-Earth trajectory, spacecraft orient themselves with the RCS (which tends to be a pretty low-powered affair) and then engage a larger rocket engine for the big-deltaV burn. -- Finlay McWalter ☻ Talk 16:45, 3 October 2010 (UTC)[reply]

I should mention that, while gimballing is very popular, it's not the only option. Gimballing requires either rotating the whole engine (which is pretty impractical for a serious rocket) or rotating the engine bell (which requires an articulation, which can be tricky to get right given the pressures and temperatures involved). Other options include vernier rockets to turn the rocket (they're a bit like the RCS, above) or putting robust vanes into the exhaust stream (that's how a V-2 rocket steered]]). Lastly you might consider movable fins (or fins with movable flaps) but they become ineffective in the higher reaches of the atmosphere, so they're mostly found on low-level devices like short-range missiles. http://exploration.grc.nasa.gov/education/rocket/rktcontrl.html has more. -- Finlay McWalter ☻ Talk 16:54, 3 October 2010 (UTC)[reply]

Skimming the lengthy users' manual for the Long March 3A rocket that launched Chang'e 1, it seems the first stage is steered by gimballing (and the wording suggests they do gimble the whole engine, despite my claim that this is impractical☻), and that the second stage is controlled by verniers. The first stage has little fins, but these appear to be fixed and so only for basic stabilisation. -- Finlay McWalter ☻ Talk 17:04, 3 October 2010 (UTC)[reply]

Fins would in any case I presume be only effective while the trocket was travelling through the atmosphere, which is a very small proportion of its journey. --rossb (talk) 17:55, 3 October 2010 (UTC)[reply]

Rockets spend a sufficient time at a low enough altitude that some designers have felt it beneficial to include aerofins; in some cases steerable ones. Saturn V had aerofins (although the article says that future flights might have removed them, as they "turned out to provide little benefit when compared to their weight". The LM3a has them, and the users' manual for the Soyuz-U says "Attitude control is carried out through two movable vernier thrusters and one aerofin [that's for each of the 4 boosters]. Three-axis flight control is made possible through these eight engines (two per booster) and four aerofins (one per booster)". N1 didn't and Ariane doesn't (as far as I can tell). Indeed it doesn't seem worth the bother, but who am I to argue with Von Braun and Korolyev :) -- Finlay McWalter ☻ Talk 18:38, 3 October 2010 (UTC)[reply]

I'm going to jump in with a follow-up question of my own: how do they control the rocket attitude just at launch? It seems to me that even a tiny imbalance in the thrust while it's sitting still or barely moving would tip the whole thing over. This seems much different than guiding the rocket in flight. Franamax (talk) 19:14, 3 October 2010 (UTC)[reply]

The engines gimbal even while it's still on the stand. If you watch a video of an Apollo or Shuttle launch, you see the main engine bells move around after they light, as the engines take over responsibility for keeping the vehicle righted from the stand. For a second or so the rocket hovers over the blast pit before it lifts. It's probably easier than in flight, because there's no dynamic pressure imbalance trying to pitch the rocket. This kind of dynamic hover behaviour is more evident in rockets like Delta Clipper and Pixel. -- Finlay McWalter ☻ Talk 20:32, 3 October 2010 (UTC)[reply]

They had computers that could handle that — reliably — in the 1960s? --Trovatore (talk) 20:54, 3 October 2010 (UTC)[reply]

Seems like a pretty basic feedback-based system: "gyroscopes in nose are reading tilts of (x,y) (or even better, are reading change in that direction), start moving rear thruster more in the direction of (x,y)". As long as rocket is tilted in that direction, the thruster will keep pushing more and more in that same direction until there's just enough torque around the center-of-gravity to start correcting the tilt. It works fine as long as you're dealing with "small" changes. If you tilt too far over and/or don't have limits on the rates of change, gets scarily easy to over-compensate and swing out of control...just like driving on ice. All sorts of inertial guidance systems even for following a complex route are at heart just a difference amplifier that reports "target-value minus current-value" and the result piped to whatever mechanism steers "away from off-course". I've seen the airplane analog ("adjust flaps/rudder to make the plane do exactly what the pilot says to do", which means need feedback-control to make "actual plane" match "pilot action" to negate wind effects) in intro-engineering courses. DMacks (talk) 21:28, 3 October 2010 (UTC)[reply]

Never mind 1960s, a V2 rocket had to do that in the 1940s, so clearly no computer. It's a damped feedback system running off a gyroscope (over damp it and it's underreactive and a breeze blows it into the stand; under damp it and it over-reacts and does a little somersault into a school). What's impressive is not that they could do this in the 1960s with transistors, but that they could do it in the 1940s with, well, I don't know. Baling wire and little pulleys, perhaps :) -- Finlay McWalter ☻ Talk 21:11, 3 October 2010 (UTC)[reply]

There is a film for the V1 rocket on youtube (watch?v=HQccOvNG_ZY) which gives the pneumatic steering mechanism for the V1. There is a gyroscope which is driven by pressured air in a tank. The whole "guiding system" is pneumatic. So you would need no computer or even electricity for the guidance. --Stone (talk) 06:51, 4 October 2010 (UTC)[reply]

That's why they call it rocket science! Actually, this is control theory, (arguably the most important subset of rocket science). For every time-step "t", what set of input signals are necessary (valve settings; mechanical actuators; and so on), are required to guarantee stability, both mechanically and thermodynamically, for the rocket? The difficulty is that certain outputs (like rocket attitude and real-time thermodynamics of the combustion chamber) are impossible to know exactly until the instant of ignition; so a sophisticated bit of engineering goes in to providing a feedback loop from sensors back to the control algorithm. Control theory was designed long before engineers had knowledge of computers; very sophisticated systems can be built using simple electronic amplifiers and even mechanical governors. Now that everything is digitized, we can control at higher frequencies and to higher degrees of precision; in the case of rocketry, though (especially the attitude-control of large rockets), many parameters are physically large - so the relevant frequencies are very low (maybe tens of hertz). For this low-frequency control, gigahertz-speed computers aren't needed. On the other hand, the thermodynamics inside the combustion chamber can occur very fast, so it is useful to monitor it at very high speeds. However, control of these parameters is limited - valves that are controllable at hundreds of hertz do not exist, so this limits the utility of a fast computer. Safety and "emergency shutdown" has improved since the 1950s, though, as unstable combustion can now be detected mere nanoseconds after the chemistry starts going haywire, and a computer can make a decision (for example) to shut down or detonate the rocket before an uncontrolled flight becomes catastrophic. Nimur (talk) 18:44, 4 October 2010 (UTC)[reply]

The Merlin rocket engines of SpaceX's Falcon 9 (next launch expected in November), while gimballed, also pivot their turbo-pump gas generator exhaust for roll control. -- ToE^T 00:24, 4 October 2010 (UTC)[reply]

You may also wish to read Pendulum rocket fallacy. Ariel. (talk) 01:09, 4 October 2010 (UTC)[reply]

Resolved

 – Asked and answered. That the questioner doesn't want to read the answer is not a refdesk concern. DMacks (talk) 19:23, 3 October 2010 (UTC)[reply]

What are the alternatives? --178.98.78.190 (talk) 17:03, 3 October 2010 (UTC)[reply]

Uh. doesn't the article clearly say in the lead? Nil Einne (talk) 17:45, 3 October 2010 (UTC)[reply]

I don't read the articles; they're full of inaccuracies. But thanks. :) --178.98.78.190 (talk) 18:26, 3 October 2010 (UTC)[reply]

Nil Einne I just checked, the article lead doesn't say it sucks as* at all! Should we add that in? ;) Franamax (talk) 19:18, 3 October 2010 (UTC)[reply]

Wikipedia is not censored, so we should expand the wild-card to its actual value, which I expect is 'asphalt', or possibly 'asymptotes'. --Ludwigs2 19:59, 3 October 2010 (UTC) [reply]

More likely to be Asperger's syndrome... Physchim62 (talk) 20:17, 3 October 2010 (UTC)[reply]

If you can find a reliable source perhaps. On a related note, when asking for alternatives it's generally better to explain in more detail what your problems are, since it may enable people to give better answers. To give a simple example, even if we know Ubuntu 'sucks as', it doesn't help us know which of the hundreds or whatever Linux distros may suck less for you. Nil Einne (talk) 06:04, 4 October 2010 (UTC)[reply]

I am looking for reliable sources giving or commenting on estimates of the percentage of global atmospheric oxygen produced by Algae. I mean Algae, as they are defined in the article's lede: excluding the prokaryotic blue or blue-green "Algae". Thank you in advance, any help is appreciated (including references that say it is impossible to give a meaningful estimate).---Sluzzelin talk 17:05, 3 October 2010 (UTC)[reply]

This article states about 60%, might be a starting point for further searches. PЄTЄRS J VЄСRUМВА ►TALK 17:59, 3 October 2010 (UTC)[reply]

On a side note, the global measured population of plankton, which includes eukaryotes including plant algae has declined by 40% within the last six decades. ~AH1^(TCU) 18:14, 3 October 2010 (UTC)[reply]

Thanks to both of you. ---Sluzzelin talk 08:19, 5 October 2010 (UTC)[reply]

Will stopping or declining of masturbation effect in increasing one's level of testosterone and, subsequently, more male-like behaviour? —Preceding unsigned comment added by 83.31.134.230 (talk) 19:27, 3 October 2010 (UTC)[reply]

Perhaps it will do the opposite. --178.98.78.190 (talk) 20:24, 3 October 2010 (UTC)[reply]

No it will not. I think it would probably do the opposite. It will, however, increase the amount of ejaculate next time you ejaculate, as it's stored up.--92.251.236.197 (talk) 20:28, 3 October 2010 (UTC)[reply]

Lack of orgasm might cause increased testosterone level and increased sexual drive. Edison (talk) 00:13, 4 October 2010 (UTC)[reply]

As our article on testosterone points out, variations in levels are due to a much wide range of causes than frequency of orgasm. Physchim62 (talk) 00:43, 4 October 2010 (UTC)[reply]

As an aside, there is some evidence that regular ejaculation reduces your chances of getting some types of prostate cancer. See Prostate_cancer#Ejaculation_frequency. There is no requirements as to the cause of this ejaculation, so whether it is done alone or in conjunction with another consenting adult, the benefits are the same. This effect has not been explained mechanistically, but it may have something to do with regulating testosterone levels in the body. --Jayron32 16:17, 4 October 2010 (UTC)[reply]

October 4

In my chemistry textbook the SI (or metric) is referred to as the 'logical system of measurement'. But how logical is it, really? Far more than the wretched English system (or so I've been told since kindergarten), but not as logical as they could be. The different unprefixed units do not coincide: a gram is intuitively "small" whilst a litre and a metre are intuitively "middle-sized" or even "somewhat large". So my question is: when the French scientists were inventing the SI, why didn't they make 1 m³ = 1 l, which would also be 1 kg of some common substance (most likely water)? Wouldn't this be more logical? Thanks. 24.92.78.167 (talk) 00:44, 4 October 2010 (UTC)[reply]

A partial answer is that they were chosen to be at least within an order of magnitude to the traditional units being used in Europe at the time. For example a Liter is pretty close to both a french pint and a french litron. I'm sure this made it a lot easier for people to adopt the new units. (The french pint is almost double the American pint, in case you were wondering.)

This system was originally designed to simplify trade, not specifically science, so it was built around the needs of whatever merchants needed the most. APL (talk) 01:15, 4 October 2010 (UTC)[reply]

I agree with APL's answer, with the exception that the litre is not an SI unit, though it is commonly used with other SI units. -- Scray (talk) 03:48, 4 October 2010 (UTC)[reply]

Ah, you're right. Stupid of me. ... ... Still, it is a metric system unit. So I still feel justified in using it in a discussion about the origins of SI units. APL (talk) 04:34, 4 October 2010 (UTC)[reply]

What is logical to one person is not logical to another. Consequently I think it would be impossible to contrive a system of units that would be universally considered logical. For example, if one cubic metre was equivalent to one litre, and one litre was about the size of the present litre, the metre would be only one tenth of its present size — one new metre would be equal to the present decimetre. This might be logical to scientists working on a small scale in laboratories, but it is unlikely to be logical to sailors and travellers who would find a day's journey measured in numbers ten times greater than the present numbers. A man can walk ten or twenty kilometres during the course of a day's work. He is unlikely to find it logical if he found himself walking one or two hundred kilometres in a day's work. Dolphin (t) 05:43, 4 October 2010 (UTC)[reply]

Only because he is accustomed to 100 km being a very large distance... Googlemeister (talk) 13:42, 4 October 2010 (UTC)[reply]

It's worth remembering the gram is not the SI base unit of mass. The kilogram is. This is generally accepted as an unfortunate artifact of history. For some history see [15] (surprisingly I couldn't see much coverage of this in our articles). Nil Einne (talk) 05:55, 4 October 2010 (UTC)[reply]

I think the explanation for why such a small size was chosen for the gram must be that the prefixes for scaling originally ran only from milli- (1/1,000) to kilo (1,000). If the kilogram had been named the gram, there would have been no names available for any units smaller than what we actually call a gram -- and presumably these were needed even then in fields like chemistry and medicine. --Anonymous, 06:44 UTC, October 4, 2010.

Our Grave (unit) article does discuss this, but perhaps some of it should be folded back into the kilogram article. CS Miller (talk) 11:27, 4 October 2010 (UTC)[reply]

Thanks. I thought I remembered reading something before but didn't find anything in the obvious places so decided I remembered wrong. I skimmed too vast so missed the mention of grave in kilogram. Nil Einne (talk) 13:57, 4 October 2010 (UTC)[reply]

I think "logical" here just refers to the ease of conversion between measures. If you want something "more logical", you can have a look at Planck units, but I doubt those are convenient for everyday use... Jørgen (talk) 07:19, 4 October 2010 (UTC)[reply]

Offtopic, but do people really walk 10 or 20 km during a day's work? --Chemicalinterest (talk) 11:22, 4 October 2010 (UTC)[reply]

I wrote A man can walk ten or twenty kilometres during the course of a day's work. Your question is off-topic. Dolphin (t) 11:25, 4 October 2010 (UTC)[reply]

10-20 is easy for some professions. I used to do that much in one shift. I used to know one woman who, if she didn't do something like 50 miles in a week, would make it up on the weekends. She rarely had to do any "extra" walking on the weekends to get to that figure. Additionally, some mail carriers probably do at least that. Dismas|^(talk) 11:50, 4 October 2010 (UTC)[reply]

The SI and the metric system in general is logical only insofar as all base units can be converted to any other by multiplying or dividing by a multiple of ten. Math becomes trivial when all you have to do it move a decimal point. As with any system, it needs to balance its usability from a mathematical perspective, and from a practical perspective. A measurement system isn't very useful if every measurement in it requires really huge or really tiny numbers. There are some base metric units which suffer from this problem, the pascal is an impractically small unit of pressure, which is why we use bar or kilopascal. Grams are impractical when weighing anything large (like, say, you) , so we use kilograms in SI. See also cgs system for details on a related system of measurement for small items. See also Planck units for a system which is mathematically practical, in the sense that ALL of the five major universal constants are defined as "1", but which is not very usable on a daily life since it requires the units themselves to be impractically tiny.--Jayron32 16:13, 4 October 2010 (UTC)[reply]

If you are measuring in a way that requires lots of halving and doubling it would be more logical to have a base more easily halved and doubled into whole numbers than base-10. Inches (12) and yards (32) are easily to halve into simple fractions than base-10 SI units. At least, I've always found that to be the case. Somehow it seems easier to quickly grasp what 1/16th is over 0.0625. And five 16ths is obviously 5/16, while 5 * 0.0625 is... um, er... hmm. Pfly (talk) 11:25, 5 October 2010 (UTC)[reply]

Why is it that if an adult gets the saliva of an HIV infected person in his/her mouth by kissing, he/she will most likely not get infected. But if a child drinks breast milk of a mother with HIV, he/she will probably get infected. Doesn't the virus get destroyed in the stomach? —Preceding unsigned comment added by 76.169.33.234 (talk) 02:15, 4 October 2010 (UTC)[reply]

There are several factors involved. It is possible for a child to be infected from breast milk, but most maternal infection occurs during childbirth. In any case, the probability of a child being infected by an HIV-positive mother is only about 25%, even with natural childbirth, and cesarian section lowers that figure dramatically. Breast milk may or may not contain more virus than saliva, I don't know, but the length of exposure during breast feeding is far longer than for most kissing. The virus does get destroyed by the stomach – infection in these cases is thought to be through small wounds in the mouth. Physchim62 (talk) 02:43, 4 October 2010 (UTC)[reply]

(to the OP)I think you're overstating the risk from breastfeeding: 6 weeks of breastfeeding for children of HIV-positive mothers in Zimbabwe carries about 5-10% risk of infection (PMID 20121424). It is true that breastfeeding is much riskier than kissing, so it's worth discussing, as follows.

Saliva contains very low levels of HIV, when it's present at all: in one study (PMID 12907539) on HIV levels in a variety of fluids taken from people with HIV, only about 5% of parotid saliva specimens contained detectable HIV RNA, and even when detected the mean viral load was only about 200 copies/mL fluid (estimated from figure 1). When one considers the volume of saliva exchanged, we're talking about a very small amount of virus. If we (over-)estimate 10 mL of saliva exchange, that's about 2000 copies of HIV in the 5% of the time that it can be detected (i.e. on average, there would be close to zero per exposure). There are quite a few papers documenting antiviral properties of saliva (e.g. PMID 7615818, PMID 2078420, reviewed in PMID 10401522). Whatever the reason, kissing is considered not to be risky for HIV transmission if blood is not transmitted.

Breast milk contains much more HIV, with levels over a 6-week period in one recent study (PMID 20121424) averaging 1.8 log₁₀ (63 copies/mL). A baby ingests about 100 mL of breast milk in a feeding, which would mean that more than 5000 copies of HIV are ingested per meal. As that report summarizes, there are many things that are not explained about the transmission of HIV by breast milk, including the paradox that exclusive breastfeeding seems to carry a lower risk of HIV trasmission than mixed feeding (breast and bottle feeding). It's easy to make guesses as to why this might be true, but the answer is not known. -- Scray (talk) 03:43, 4 October 2010 (UTC)[reply]

So would the small chance of infection from breast milk happen because a cut in the mouth? —Preceding unsigned comment added by 76.169.33.234 (talk) 09:05, 4 October 2010 (UTC)[reply]

I was always under the impression that HIV cases in children were mostly caused by crossing of the virus to the baby via the placenta? I'm not sure why breast milk would be any more significant than any other fluid in carrying HIV; assuming no cut, why doesn't the virus just break down in the stomach? Regards, --—Cyclonenim | Chat  10:42, 4 October 2010 (UTC)[reply]

If the virus could cross the placenta, infection rates of children would be 100% (or as near as makes no difference), and you wouldn't see an advantage for cesarian sections. Physchim62 (talk) 10:46, 4 October 2010 (UTC)[reply]

Fair enough, as I said it was just an impression I was under. Clearly I was mistaken. I'm sure it does cross in certain cases though, right? Regards, --—Cyclonenim | Chat  12:52, 4 October 2010 (UTC)[reply]

Yes, HIV is listed in the "other infections" category of the TORCH complex of perinatal infections than sometimes cross the placenta, so it's not 100% sure. However, my impression was that the main route of infection was through abrasion during natural childbirth: you don't need a bleeding cut for the viraus to gain access to the bloodstream. Physchim62 (talk) 13:53, 4 October 2010 (UTC)[reply]

Bear in mind that the baby's digestive system is designed to allow intact proteins (antibodies) into the body as a method of passive immunity. To quote from one source, 'At birth gastric pH ranges from 6 - 8 due to residual amniotic fluid in the stomach. (Amniotic fluid is regularly swallowed during intrauterine life.) Gastric pH then falls to a pH of 1.5 to 3 within 24 to 48 hours after birth but during the first week of life returns to neutrality. Gastric pH then decreases gradually to adult values after approximately 2 years of age (range 3-7 yrs). This higher pH which normally occurs during this time is referred to as a "relative achlorhydria".'[16] According to PMID 10099107 the virus does enter via the gastrointestinal tract, though the exact cell type was unknown as of 1999. Due to a lack of inspiration on search terms I haven't tracked down the pH needed to kill HIV, aside from one curious advocate of using lemon as a contraceptive and antimicrobial, who claims lemon pH (which adults but not babies will have in the stomach) kills HIV in two minutes.[17] Wnt (talk) 16:22, 4 October 2010 (UTC)[reply]

What is the probability that small, well-hidden nuclear weapons have already been strategically pre-positioned in urban centers around the world by one or more nuclear-weapons-capable nations? WikiDao ☯ (talk) 03:26, 4 October 2010 (UTC)[reply]

Who can say? What possible evidence could there be? Were such a device ever found, would anybody announce it? But I think it's safe to assume "basically zero". — Lomn 03:47, 4 October 2010 (UTC)[reply]

I'm not asking for a prediction, but for an estimation. On what basis would you expect that probability to be so low? WikiDao ☯ (talk) 03:54, 4 October 2010 (UTC)[reply]

Because the longer you leave them sitting around, the higher the chance that somebody will find one, and if somebody finds one, there will be hell to pay. They aren't very easy to hide: unless you encase them in massive amounts of lead, the radioactive materials will show up bright and clear on a radiation detector. Looie496 (talk) 04:21, 4 October 2010 (UTC)[reply]

Sources for likely OGA response? Sources for ease of securely hiding a device that's been well-engineered for its purpose by nations with a nuclear-weapons-capable level of technological sophistication? WikiDao ☯ (talk) 04:38, 4 October 2010 (UTC)[reply]

I don't have good sources either, but I'll venture to speculate anyway. One thing is that nuclear weapons have a limited shelf life. Thermonuclear ones containing tritium need to have that stuff replenished from time to time. Just plain plutonium, I think, loses some of its power in storage over the years as well. But above that there would be the positioning of the device. As pointed out earlier, it would have to be pretty well hidden. And nuclear weapons are most effective against non-hardened targets, such as cities, when detonated at a considerable altitude above the target. Blowing up a smallish fission bomb in the basement of a Manhattan skyscraper would certainly bring down that building and do a lot of damage, but it wouldn't be quite as spectacular as a good blast at 2,000 feet. I think. But as I said, I can't point to sources, this is all just based on stuff I think I know about nuclear weapons. I'm sure there are a lot of unknown unknowns out there, at least unknown to us civvies.--Rallette (talk) 05:09, 4 October 2010 (UTC)[reply]

Any bomb that needs tritium needs to have it replaced pretty often. But you could design a bomb that didn't need tritium. Plutonium aging raises the uncertainty of the total yield, but probably not to unacceptable levels. (And you could use HEU, which is not as problematic as plutonium.) As for the effects, it depends on what you are trying to accomplish. If the goal is just "kill enough people to make a point," you can do that pretty easily. A bomb with 100 tons of TNT yield somewhere on Wall Street could probably kill 10,000 people and require billions in cleanup (at least, that's what Ted Taylor was famous for saying). That's not as bad as it would be if it was a megaton nuke put at a desirable altitude, no, but it's pretty bad. --Mr.98 (talk) 12:17, 4 October 2010 (UTC)[reply]

This looks to me like the Argument from ignorance. Firstly, there is an implied proposition — there might be nuclear weapons placed in urban centers by hostile nations, and they are so well-hidden that no-one living in those urban centers knows they are there. Secondly, when several Users say they think the likelihood is extremely low they are asked to provide the basis on which they expect that likelihood to be low!

WikiDao has implied the proposition that there might be nuclear weapons in urban centers, so well-hidden that no-one knows they are there. The principles of logic require that WikiDao must provide some substance to support his proposition. If WikiDao is unable to provide some substance his proposition must be seen to be very weak. Scientific skepticism becomes highly relevant. If other Users are unable, or choose not, to provide something to substantiate their opposition to WikiDao's proposition, that is not evidence in support of the proposition.

Despite WikiDao's challenge to us skeptics to provide substantiating information, it is WikiDao who must provide some reason as to why we should even begin contemplating his proposition. Dolphin (t) 05:27, 4 October 2010 (UTC)[reply]

Dolphin, I am simply wondering if a) it is possible to produce a nuclear weapon capable of being well-placed in a large city and capable of strategic levels of disruption to that city, and 2) whether it would make any sense for anyone to do so if they could. On the basis of information available to you, can you assess the joint probability of those two cases? And from that estimate, if non-zero, and the number of nations for which it would be both possible and advantageous to do such a thing, how likely is it to have been done already? Do I really need to justify my question any further for it to merit a response here at the WP Science Desk...? WikiDao ☯ (talk) 05:52, 4 October 2010 (UTC)[reply]

Your original question was based on the expression weapons have already been strategically pre-positioned ... and asked for a probability. For reasons I have explained, I consider your request to be illogical. I concede that it is reasonable to ask whether this event could occur in the future, but your original question did not talk about possibilities for the future, it talked about something that has already happened, and you asked for the probability. I'm pleased to see you have transformed your question so that you are now asking about the feasibility of an event occuring in the future. Dolphin (t) 06:16, 4 October 2010 (UTC)[reply]

In frequentist terms this question does not make sense, but in terms of Bayesian probability, it does. Not that that makes it clear how you'd give a defensible answer. --Trovatore (talk) 06:34, 4 October 2010 (UTC)[reply]

A reasonable answer would be in terms of how strategically useful such a device would be given how technologically likely it would be (given publicly-available information) for an easily-hidden, affordable, and strategically "effective" device to be developed. I am assuming such an assessment can be roughly made for the present time, without undue regard for the unknown aspects of that possibility pertaining to either past or future technology. It really does not seem to be such a difficult question to answer as responses so far have seemed to try to make it appear to be for some reason. WikiDao ☯ (talk) 07:44, 4 October 2010 (UTC)[reply]

For aging ("limited shelf-life") issues, see JSR-97-320, January 1998. Assume details of that kind to be well-understood by nations capable of developing and placing such devices in the first place (assuming nations with such technological sophistication exist, of course; I propose this to be a self-evident truth). My point is that it is technologically feasible for such a thing to be done – even if, like all useful nuclear-weapons technology, it also tends to be expensive. Is the skepticism here due to an expectation that such a pre-placement of nuclear devices would not be strategically worth the expense of developing, placing, and maintaining them...? Or that it is simply not possible somehow on technological grounds to do so? WikiDao ☯ (talk) 05:39, 4 October 2010 (UTC)[reply]

Self-evident, how so? That report, while 12 years old, pretty much concludes that "we" (the U.S.) don't really understand how plutonium ages, although aging of about twenty years did not seem to affect the performance of nuclear weapons.

I'm just very skeptical about the strategic value of such a program, as you put it, and not least because of the potential for technical problems, nuclear or otherwise. As the same report notes, the non-nuclear parts of a bomb are at least as complicated as the nuclear ones. Even mothballing a simple truck is actually difficult, especially if you want it to start up at the turn of the key. Plastics age, seals leak, materials react with each other in surprising ways. It is questionable whether you could ever be quite confident that a nuclear weapon will remain workable (and safe!) for a long time without checking.

Even then, a bomb hidden in a fixed location would be muffled by the structure that conceals it, and could only ever be used against that target. You could use a huge bomb, but that would make it that much more difficult to get in place and conceal (plus it wouldn't be "small" anymore). Or for some flexibility, you might consider some kind of remote-controlled delivery system, which would add another layer of unreliability.

All of this meaning agents would be needed on the spot to install and then maintain it. Human agents with specialized knowledge, operating for a long time in more or less hostile territory, are a scarce resource with potentially better uses, as well as a source of risk, being only human (the successes of Al Qaeda notwithstanding).

And last but not least, if you have confidence in your long distance delivery capabilities, then the motivation will be difficult to come up with. To level a city, I'd go for missiles and planes. And for counterforce purposes, well, zero warning time would be great to have, but cannot be achieved in this way. In sum: if you're Russia or China, you don't need it, and if you're North Korea, you probably can't do it. All of which is not to say such a program is impossible; the V-2 had little military value but the Führer apparently just thought it was cool. Now smuggling a couple of suitcase bombs into an enemy country, to be used by agents in time of conflict as the need arises, that might be a workable idea.

But what do I know? These are mainly just objections I've come up with when considering the same idea myself some idle afternoon.--Rallette (talk) 07:31, 4 October 2010 (UTC)[reply]

(Whoops, I misread your "self-evident" statement. Sorry about that.--Rallette (talk) 07:46, 4 October 2010 (UTC))[reply]

Those are some good initial thoughts on this, Rallette. ;) Regards, WikiDao ☯ (talk) 07:48, 4 October 2010 (UTC)[reply]

For the record, my answer (pending further discussion;) is: near 100%. WikiDao ☯ (talk) 07:52, 4 October 2010 (UTC)[reply]

Effective further discussion that would dissuade me from that view would include explanations as to how: 1) such a thing is either technologically and/or financially implausible and 2) it would not be strategically advantageous for any country that can get past 1) to actually do it. WikiDao ☯ (talk) 08:05, 4 October 2010 (UTC)[reply]

How the hell did you reach a conclusion of nearly 100% from the above discussion? The probability of nuclear weapons being concealed in cities is not zero, but it's no where near 100% either. Suitcase bombs were designed so that an agent could go and place them at a location and set a timer on them, but this is very different to just putting a bomb somewhere and leaving it for an unspecified period of time. To address your questions, no it's not financially impossible, and no it's not technically impossible. That doesn't provide any evidence for your theory, though. Why put a weapon in a concealed place where it is going to do significantly less damage and be less reliable than conventional 'drop out the sky' or submarine based nuclear weapons? Almost all strategy in the Cold War was based on the U.S. and Russia simultaneously firing nuclear weapons from missiles, not detonating ones in concealed places. That is simply very impractical from a reliability standpoint. I don't know how you think it's a near 100% probability taking this into account. Regards, --—Cyclonenim | Chat  10:38, 4 October 2010 (UTC)[reply]

This reminds me of a question I asked a while ago, Talk:Neutrino#Detecting nuclear weapons via electron antineutrinos. I can't really think of a good way to prevent hidden nukes, unless there's some way for a satellite in orbit to detect such weapons... Wnt (talk) 08:08, 4 October 2010 (UTC)[reply]

Thanks WikiDao, it's nice to know I don't waste my time in vain:) As for the strategic advantage, I had some further thoughts walking to work.

Imagine the darkest days of the Cold War, say 1981. Everybody knows that the U.S. and the U.S.S.R. are both prepared to blow the other country right off the face of the earth on five minutes' notice. Both actually believe the other side wants to do it and would jump at the chance. (Reagan evidently was deeply shocked to learn that the Soviets thought he was ready and willing to push the button.) Both also maintain that it's all for self-defence, on their own part. Now this position is morally vital, and the moral dimension is essential to strategy. Even if you're purposely incinerating civilians in Hamburg or Düsseldorf, you tell yourself it's because of the port or some tank bearing factory, military targets. Or at least you tell your people and the world that it is so. You are the good guy.

Now imagine you get caught doing something like this, planting atom bombs in cities. The risk of getting caught is always there. Even though the world has more or less learned to live with the threat of hair-trigger armageddon, it would be outrageous. And it would definitely demolish the pretence of "self-defence". The risk would be incalculable. You can spy on the other side, target their cities — but this is just not on. Absolutely unacceptable conduct for a good guy, let alone someone pretending to be the moral leader of the world.

But how about some smaller player? Now if you read (or listen — highly recommended) to what Brian Reynolds Myers has to say abut North Korea and their world view, thay might be a candidate for such a scheme. As Myers puts it, North Korean ideology is based on a notion of their own racial purity and childlike innocence, and this corresponds to their tendency to use deadly force erratically, like children: bombing passenger airplanes, sinking South Korean vessels. Stupid attacks that gain them nothing. And their missiles are anything but reliable, too. But they may not be able to pull it off.

Anyway, the way I'm taking this discussion, it will soon be kicked out of the Science desk. Maybe someone somewhere has actual hard data on which to speculate.--Rallette (talk) 10:45, 4 October 2010 (UTC)[reply]

• You think this will soon be kicked out of the Science desk?! What an extreme response. Whyever for? WikiDao ☯ (talk) 19:08, 4 October 2010 (UTC)[reply]

Rallette possibly had in mind that at the head of this Project Page it states The reference desk does not answer requests for opinions or predictions about future events. Dolphin (t) 22:13, 4 October 2010 (UTC)[reply]

Well perhaps Ralette, did, D, and I am glad you feel confident enough about your understanding of the exact meaning of RD guidelines to offer your speculation about that possibility here. I am not too sure why you would think Ralette was thinking of that though, since I am not asking for anything like baseless personal opinion or some kind of mystical "prediction" here. I am asking for a rough value for the probability of the existence of a state of things which by no means has an a priori value of zero. If you are not familiar enough with the material to offer a well-reasoned and reasonably-well-referenced answer, then you are not being encouraged to offer it anyway by anyone here. Thanks. WikiDao ☯ (talk) 22:37, 4 October 2010 (UTC)[reply]

From an historical standpoint, the question of whether Russia would smuggle in nuclear weapons to the USA as a means of effective deterrence was studied very intently in the early 1950s. The idea was that they might not be able to get a bomber over here (the Soviets had poor long-range bombing capabilities for a long time, and no operational ICBMs until 1958), they could probably smuggle a bomb (in pieces). Here's a nice article on the subject from the 1980s.

Now the overall arguments against such a scheme are:

1. Nuclear weapons are not "wooden" and don't have infinite shelf-life. This is and isn't true. You could design a pretty nasty bomb that would with a large margin of error give a significantly nasty explosion from now until the end of the century if that was your goal. Most nukes are not designed along those parameters, but that doesn't mean you couldn't do it. Over time the yield estimation gets hard to make conclusively, but figure that even a fizzle is going to give you an explosion worth 100 tons of TNT, which would be enough to deter people if it was buried somewhere in DC or New York or another dense city. (An excellent source on the subject of how dangerous low-yield nukes would be, and how relatively simple they could be, is John McPhee, The Curve of Binding Energy. It's a little out of date, now, but is still a fascinating — and scarily relevant — read.)

2. But the strategic value depends entirely on the other side knowing you've done it. A secret deterrent is a non-existent one — it doesn't deter. Of course, the whole point of a Doomsday Machine is lost, if you *keep* it a *secret*! Why didn't you tell the world, EH? But telling people, "I've hidden a nuke in one of your cities" is not a confidence builder. (Think about how flipped out the US was when the Soviets tried to put nukes 90 miles offshore.) So on the face of it this looks like a bad plan. If you put the nukes there secretly, you don't deter. If you put them there openly, everybody flips out and probably does worse for you.

3. And of course there is risk of detection, etc., but I don't think that is as high as people are making out. If you're a nation state you could hide a nuke. They are not that large or that detectable. Proper shielding from external detection would be easy — put it in a lead-lined safe, or a X-ray room. Label something boring and uninteresting: "pinball machine parts." Hire a guard for the floor and lots of alarms. No sweat. Chances of detection basically nil. You don't have to store it in the same place you'd plan to detonate it.

So as you can see I would rate the possibility of being able to technically do it very high, and the political value of doing so to be quite low. Unfortunately that is a very dangerous calculus, because we've found that again and again, assuming the other state is working from the same "rational" political model is usually wrong. Perhaps the other state in question values vengeance as high as real deterrence? What if their assumption is that they would keep the hidden nuke secret until a crisis worth revealing it? What if the guy in charge of the plan was senile or otherwise mentally unwell? There are lots of ways in which the USSR might have assumed this was a good idea. One can imagine all sorts of Tom Clancy scenarios as well, if one wants to (the Russians smuggle a nuclear weapon into some random, not-the-top US city, detonate it, claim, "we didn't do that, why would we do that?", says a Chechen did it with a stolen bomb, instability and chaos ensues as Russia uses this as an excuse to nuke Chechnya, while in the meantime Jack Ryan saves the world and gets the girl). And if it is technically possible (which it undoubtedly is), then it can't be removed from the table, at all. (Insert "China" for "Russia" if you want. Or "Israel" if you want to get all Tom Clancy. Or "France" if you want to get saucy.)

I seem to recall a very odd snippet of an article reproduced in a book which implied that JFK told someone in the 1960s that the Soviets had a nuke in New York. I think it was picked up by Newsweek as an "adorable anecdote" in the mid-1990s, and then reprinted somewhere else. Unfortunately I'm not able to remember where the "somewhere else" was. Maybe it'll come to me later today and I can source it for real. My general thought was that the article was either confused or false. But it is an interesting data point.

Anyway, the possibility of this having been done in the past is super real and considered a legitimate threat by the fine young think-tankers of the world. I'm not sure anyone outside of the intelligence sphere has any idea of how likely this is or was. I'm not sure we can quantify it the way that you'd like. I think "probably not, but possibly" is about as good as it gets, which, like everything else in the nuclear age, is maddeningly uncertain. --Mr.98 (talk) 12:13, 4 October 2010 (UTC)[reply]

I'd discard #2: a nuke isn't a Doomsday Machine, but a weapon. If the U.S. loses all patience with North Korea and begins an attack, then one could be set off, and the threat could be made that others exist which will be set off unless etcetera etcetera. Wnt (talk) 17:30, 4 October 2010 (UTC)[reply]

I'm confused about your scenario. Are you saying that DPRK would hide a nuke in US and then set it off if the US attacked? That would be outside the logic of deterrence — the US would just nuke North Korea, nobody wins. The goal of the strategic (deterrent) nuke is to not get nuked. In that sense, hiding a nuke in an embassy wouldn't help. Now, as I fully acknowledge, that requires you to actually believe in deterrence. I don't think that's necessarily a valid assumption, though. (The US certainly didn't believe in it wholeheartedly during the Cold War, in the sense that they didn't think that their capability to almost surely obliterate the USSR would actually prevent the USSR from trying to nuke them first.) --Mr.98 (talk) 00:25, 5 October 2010 (UTC)[reply]

A problem with asking this sort of question is that, supposing that this or a similar thing had been done, anyone who actually knew about it would probably be under strong compulsions (e.g. an Official Secrets Act or an equivalent) not to reveal it, even under the far-from-impenetrable cover of a user name on Wikipedia. 87.82.229.195 (talk) 13:24, 4 October 2010 (UTC)[reply]

If a state were to want to do this, why would they choose a nuclear weapon? Nuclear weapons are complicated, expensive, fairly large... A state who could smuggle and hide a nuclear weapon could easily smuggle and hide demolition charges for key buildings, or chemical weapons, or biological weapons, all of which are much cheaper and have a more predicatble "shelf-life". Physchim62 (talk) 13:37, 4 October 2010 (UTC)[reply]

"Were the Russians Hiding a Nuke in D.C.?" --Sean 14:37, 4 October 2010 (UTC)[reply]

Ah-ha! That's what I was remembering. It was TIME and not Newsweek; 2001 and not the mid-1990s. Well, that's memory for you. Still an amazingly bizarre little article. "Ho ho, I remember Kennedy telling me that the Russians had nuclear weapons in DC! What a funny anecdote of the Cold War... no need to dwell on that or look into it... keep moving, nothing to see..." --Mr.98 (talk) 15:49, 4 October 2010 (UTC)[reply]

I'm way off from the top response here, but addressing it belatedly: why do I expect that the answer is basically 0? Occam's Razor. There could be invisible purple cephalopods hidden by the Soviets under the Lincoln Memorial. However, there is no evidence to support such nor is there a compelling reason why it would be done if it could. Now, granted, nuclear weapons are real (or are at least a better hoax than invisible purple cephalopods), but the same concept holds. There is no evidence (at all). There is no compelling use case. As noted above, plenty of other delivery systems exist and are superior. So, in the absence of anything at all supporting the concept, the answer is no. They're not real. They could be real, but they're not. — Lomn 14:47, 4 October 2010 (UTC)[reply]

Thanks Lomn. I'm glad to see you've gone from a probability of "zero" to a probability of "could be". I am asking about a probability that can be derived from publicly-known technological capacity and a geopolitical assessment of national self-interest for that strategy for nations capable of it. Purple cephalopods have very limited strategic value, hence the probability for that is near zero as you surmise. You still have not explained how it would not be technologically possible or strategically advantageous to do nukes, though. And again: I am not asking you to go find a hidden nuke yourself here. I am asking you to derive a probability based on sources you can cite to back that derivation up. Could you cite a source for your opinion that even attempting such a derivation is a "screwball" idea...? Because I am not asking for your uninformed "opinion" -- and, in fact, I think it is wrong. WikiDao ☯ (talk) 16:55, 4 October 2010 (UTC)[reply]

Excellent source above, Sean: :"Were the Russians Hiding a Nuke in D.C.?" Did you read that Lomn? That's a relevant source supporting the non-screwballness of my question. Now that that's been taken care of: again, can you explain with references your opinion that the probability today is "very low" Lomn? Thanks, interested to hear... WikiDao ☯ (talk) 17:04, 4 October 2010 (UTC)[reply]

Example for Lomn: see my answer to this RD question for a rough idea of the sort of referenced calculation I am asking you to perform in response to my question here. If you cannot perform such a calculation here then there is, of course, no need for you to say so. Hope that helps. WikiDao ☯ (talk) 17:16, 4 October 2010 (UTC)[reply]

Show me hard referenced applicable numbers akin to the example above and I'll be happy to do that math for you. Until then, please don't pretend that this question is in any way related to something where referenced calculations apply. — Lomn 19:18, 4 October 2010 (UTC)[reply]

My point is that it is not impossible to arrive at a rough but reasonable estimate for the probability that I am asking about given more-or-less well-referenced information about the factors involved in that assessment. (Which again right now are basically: 1) technological feasibility and 2) strategic advantage as part of overall nuclear weapons strategy for the five (see below for where that number comes from) countries with the technological sophistication to make that feasible).

You are at least agreeing now that that probability is non-zero given the information presently available to you, is that correct? WikiDao ☯ (talk) 20:50, 4 October 2010 (UTC)[reply]

Occam's Razor is unfortunately just a heuristic, and requires you to know more information than we have here to mean anything more than "I don't know." There are plenty of reasons for there actually to be a nuke hidden in the US — plenty of historical reasons, technical reasons, etc., and the lack of evidence doesn't mean one should rule out the possibility. Occam's Razor works great for philosophy but not for real-world events. There are plenty of "why" reasons which I and others have pointed out. The Soviets had nukes in 1949 but no delivery system that could reach the US until 1958. That's ten years where they had no credible deterrent while the US was basing nukes in Europe. In the 1980s, the US had a huge advantage in its ability to launch a sneak attack against the USSR because of its Pershing-II missiles based in Europe. The USSR had nothing comparable and was scared stiff that the US might just launch a decapitation attack. To me, either of these could be good "whys". You hide the nukes, don't tell anyone. If the US looks like it is starting to rev up its first-strike action (not a crazy possibility, and something that was considered as very real option by a number of US administrations, certainly by the Department of Defense), you kindly slip the word that there's a nuke hidden in DC and that they should not be so confident in their abilities. Not the worst strategy in the world, when it comes down to it. Helluva lot cheaper than ICBMs! --Mr.98 (talk) 15:53, 4 October 2010 (UTC)[reply]

With that scenario Mr 98, actually having the nuke hidden there would not strictly speaking be necessary, as it must only be a credible threat, not an existent one. Googlemeister (talk) 19:25, 4 October 2010 (UTC)[reply]

True, and an important point when considering the importance of any nuclear blackmail threat. --Mr.98 (talk) 21:01, 4 October 2010 (UTC)[reply]

A somewhat easier scenario would be a device on the seafloor just offshore, or in a harbor, that could be emplaced by submarine. We know of many sea-floor intelligence-gathering systems. A sub-aqueous explosion would be less effective than an aerial burst, but would certainly wreck anything in or near the water, and the displaced water would be full of fission products. Operation Crossroads Baker provides a model. Acroterion _(talk) 18:15, 4 October 2010 (UTC)[reply]

But a seafloor device could probably be detected/found/stolen/monitored. A device in the basement of the Russian embassy, not so much. --Mr.98 (talk) 21:01, 4 October 2010 (UTC)[reply]

True, but it could be arbitrarily large, and they're not that easy to find in all the submerged junk around a harbor. Note that the Air Force lost an H-bomb in the 1958 Tybee Island B-47 crash and have never found it, despite more than one search. One pre-ICBM scenario was for Russian submarines to fire nuclear torpedoes into, say, New York Harbor. Acroterion _(talk) 21:47, 4 October 2010 (UTC)[reply]

It's possible. It just seems riskier than keeping it in an embassy basement or attic. The second you put that nuke in the water, it's out of your direct observation and knowledge. (Unless you watch it all the time, which might attract attention!) Additionally, the US is rather notorious for its clever ways of technologically detecting things, its recovery of valuable stuff deep in the ocean, and its obsessive funding for seafloor mapping. If I were a Russian, I wouldn't bury a nuke in a harbor. If the US did find it, they'd probably disable it and never tell you, and so you'd think you had an asset when you didn't. That kind of possibility keeps NKVD/KGB folk up at night. If I were a Soviet spook, I'd want my nuke somewhere that the KGB could check on it whenever they wanted to, and somewhere where the conditions were more controllable. --Mr.98 (talk) 00:31, 5 October 2010 (UTC)[reply]

Yes, Mr.98, I agree.
I think one of the main objections above, though, is "what would happen if you got caught?". And the opinion seems to be that the world would be made to know that you'd been caught, and the world would be angry at you for it. I think the assumption that the world would necessarily be made to know about it is false.
Also: what is the marginal cost of producing such a weapon once you have the technological infrastructure to produce them? Or: how many of them could a nation with such an infrastructure afford to produce? Given that number, how likely is it that at least one has been placed by at least one such country? WikiDao ☯ (talk) 18:00, 4 October 2010 (UTC)[reply]

The "getting caught" question is a good one and one that I'm sure the policy wonks would love to spin out. You have really a few sub-questions in there: 1. what is the likelihood of getting caught? 2. what is the likelihood of anyone being able to prove that you've done it? 3. what is the likelihood that a state (like the US) would confront you on the issue publicly rather than just keeping it in mind as they deal with you (or reciprocate)? I'm not sure we know any of those, but it's worth remembering that the Cuban Missile Crisis was done under the (false!) impression that they hadn't yet put nukes in Cuba. Things would have likely had been different if they had known that there already were nukes in Cuba.

As for the marginal cost of producing a suitcase nuke... not very much. A small amount of plutonium or HEU, some high explosives, some know-how. Plutonium and HEU are expensive but once you have the factories to make them in bulk, it's no big deal. Producing them would not be at all a hindrance for any nuclear power, even lesser ones. Cost of production does not really factor into how many there might be. Nations like the US and Russia and China have plutonium and HEU measuring in tons just on hand and sitting around. It takes 10 kg or so to make a bomb. It's probably not likely that they would make huge numbers of such weapons — that's very dangerous and there's a huge chance of one of those getting stolen or misused or whatever if you make thousands and thousands of them. --Mr.98 (talk) 18:18, 4 October 2010 (UTC)[reply]

Ok. So, I'm getting the sense that your answer to the question at this point is "non-zero", correct? And would you say that's roughly a high non-zero or a low non-zero? WikiDao ☯ (talk) 18:51, 4 October 2010 (UTC)[reply]

My total guess would that it would be counted in the dozens but not the hundreds, if that is what you are asking. It's the kind of thing where you'd say, "let's make 10 of them, just to have them," but saying "let's make 100" is an invitation for real trouble. That's just a speculative production guess, not a deployment guess. I think the odds of them deploying more than one or two of such things are probably very low, if they were to deploy any such things. The strategic effect would really be achieved by saying "DC and New York" and being done at that. --Mr.98 (talk) 21:01, 4 October 2010 (UTC)[reply]

I meant "non-zero" as an answer to my original question. WikiDao ☯ (talk) 21:21, 4 October 2010 (UTC)[reply]

Oh, OK. Yes, I would say, "non-zero chance" that it was done in the past and that said weapons might still be in place. As for low or high... I don't know. There are a lot of mixed signals out there, a lot of possibilities. In a practical sense I'm not sure it matters. Starting a "shooting war" with Russia (or China) would be idiotic and suicidal either way. I don't think that either nation would endanger its own livelihood by making any pre-placed weapons vulnerable to theft, sabotage, misuse. If there are such things, there are probably not many of them, and they are probably pretty tightly controlled and only know about by a few people. I wouldn't let the idea of a pre-placed nuke dictate strategy any more or less than one on an ICBM or SLBM. --Mr.98 (talk) 00:14, 5 October 2010 (UTC)[reply]

Ok. I'm still thinking "highly probable" myself for a number of reasons, but would be happy to be convinced otherwise by well-sourced reasoning concerning the technological (including detection-countermeasures, fail-safes, command-and-control systems, etc.) and strategic policy issues involved. And I am not prepared yet to further consider the advantages or feasibility of this strategy to "non-acknowledged" states like Israel, India, Pakistan, ...

Hoping at this point that someone weighs in with a good source or two on the policy issues (below). :) WikiDao ☯ (talk) 00:24, 5 October 2010 (UTC)[reply]

In Brad Thor's State of the Union the Russians hid them in mausoleums all over the US. Beach drifter (talk) 18:48, 4 October 2010 (UTC)[reply]

Further consideration

For one of the factors in this assessment, let's say there are only five nations at present with the acknowledge-able technological capacity to easily produce enough such weapons to suit their strategic interests: US, Russia, UK, France, and China. And let's say each of these five could produce "many" should doing so indeed suit those interests. So it is coming down to how advantageous this strategy would be for at least those five nations. Does anyone have any sourced indications of how likely it is for that to be advantageous in that way...? WikiDao ☯ (talk) 19:27, 4 October 2010 (UTC)[reply]

It would be less advantageous to hide a nuke for one of those nations then it would be to use a missile delivery system. Consider the following. If you hide one, you run several risks. Risk of getting caught smuggling it in. Risk of it being found by the government and exposed. Risk of it getting found by criminals and stolen. And weigh those risks against the risk of you keeping it attached to an accurate delivery system in a secure location, always ready to place it anywhere on earth in 20 minutes or less. Add to that, governments do not like one person to control a nuclear device, and that would add a further layer of complexity to the hidden warhead scenario. Because of the balance of these equations (which admittedly are difficult to quantify), I would place the odds of a major warhead producer hiding warheads in the cities of potentially hostile nations at about the same likelihood that the assassination of JFK was a mistake and that Jackie Kennedy was the intended target. Googlemeister (talk) 19:37, 4 October 2010 (UTC)[reply]

See our Brinkmanship article for a sense of the tolerance for risk in strategic geopolitical affairs. And I am not sure what you believe would actually happen if a device were discovered by a nation (eg. in the basement of some foreign-owned building, like a consulate or embassy or "safe-house"...) or on what basis you believe that would happen. Your point about the need for a variety of fail-safes in the system is a good one, but hardly an insurmountable obstacle given the level of sophistication of the nations currently being considered. And delivery by missile or aircraft has several disadvantages (even just at present, and potentially still more so as time goes on) compared to having nukes already in place. Thank you for your thoughts though, GM :) WikiDao ☯ (talk) 20:18, 4 October 2010 (UTC)[reply]

Brinkmanship? Try direct act of war. Googlemeister (talk) 20:27, 4 October 2010 (UTC)[reply]

Not if done subtlety. At least not any more an "act of war" than putting Pershing II's in Europe or any of the other equally dangerous/threatening things that went under the heading of "brinkmanship." --Mr.98 (talk) 21:02, 4 October 2010 (UTC)[reply]

On the contrary, they are two distinct things. In the Pershing II scenario, you are not placing weapons of mass destruction in the country of your rival, just nearby. In the basement scenario, you have essentially invaded with part of your armed forces (commandos in action if not name), which is about as traditional a casus belli as you can get. Googlemeister (talk) 21:12, 4 October 2010 (UTC)[reply]

But you can put armed forces in your own embassy, no? Anyway my point is that in real-world terms, it's not clear to me that it would be treated as an act of war. That's the thing about nukes — as Churchill quipped, the worst things get, the better they are. The more real the threat is, the less likely it will lead to actual war. So the theory goes. --Mr.98 (talk) 22:20, 4 October 2010 (UTC)[reply]

Agree with 98 on that one. :) And military activity in one country by another country without those countries being at war with each other or likely to go to war with each other as a result is hardly uncommon in this day and age, GM, when it suits the acting country's interests to do such a thing. I think there was a question here recently about US military activity inside Pakistani territory, wasn't there? Happens all the time; as would pre-placing nukes, I am saying, by countries who both are capable technologically of doing so and perceive a strategic advantage to themselves in actually doing so. And note that once it gets done, there's self-evidently not a whole lot that can be done about it, is there? ;) WikiDao ☯ (talk) 00:47, 5 October 2010 (UTC)[reply]

The logic here is rather unusual. What you are telling me is that if China wants to create a very large embassy in DC and maintain an armored division on the grounds that the US would allow that? Absurd. As for US troops violating Pakistan, that only proves my point. They have stated that Pakistani forces would open fire on US troops if they are in Pakistan. I am sure they would be much less happy about the US storing nuclear warheads on their territory. Googlemeister (talk) 13:19, 5 October 2010 (UTC)[reply]

Of those you mentioned, only Russia and China would have any real incentive to do this. Both have serious delivery issues with regards to the United States on account of it being so far away, and because US allies are so close to their own borders (in Russia's case), or, as in China's case, the crucial cities are so close to the coasts (and vulnerable to subs). There is really no advantage for the US, UK, or France that I can see. The US would have no reason for this for most of the Cold War. I don't think any power would have any real advantage in fielding this sort of thing today — the nuclear threat from the US is just not very high. --Mr.98 (talk) 20:56, 4 October 2010 (UTC)[reply]

(edit conflict) Well, there's no need for present purposes to get too probabilistically precise about that last assessment. But I wanted to directly spell out that wikilink above about some of the disadvantages of airborne delivery: "National missile defense": expensive new technology still largely in development. Issues such as that do have an impact on the strategic advantages of pre-placement, don't you agree? WikiDao ☯ (talk) 21:07, 4 October 2010 (UTC)[reply]

I will grant you, the intercepting systems may make nation states rethink their delivery systems in the future. I would even expect something like this from a non-nation, but at this time, the intercepting systems are not sufficient to intercept most ballistic deliveries in the event of a conflict. Googlemeister (talk) 21:16, 4 October 2010 (UTC)[reply]

Okay. Re. "non-state": the List of states with nuclear weapons is worth considering in its entirety, but for simplification purposes I would still like to focus for now on only the five nations already being considered. WikiDao ☯ (talk) 21:25, 4 October 2010 (UTC)[reply]

Sure, that might make a difference in evaluating the advantages, if it got to the stage where it actually seemed workable or reliable to the point that it would actually be able to stop a real attack (which current tech is nowhere near being). There are still considerable disadvantages to pre-placement, of course. --Mr.98 (talk) 22:20, 4 October 2010 (UTC)[reply]

It would be extremely easy to do and extremely useful under easily forseeable contingencies, though with dire consequences when the action was discovered. It is similar to having stealthy long-term moles in a foreign country with weapons caches, but with a much greater ability to make the host country do what you want. We know that the Soviets buried caches of guns, explosives, and money in the US during the cold war, for instance. The Russians, Israelis, Chinese, British, French, Indians and Pakastanis are known to have nukes, and some administration might think it was a good idea to position nukes in the US to exert leverage in some future situation. Then there is no need to launch missiles or to get airplanes past US air defenses. (Or Indian or Pakistani air defenses for that matter). The best method would be using misdirection, like hiding a Soviet suitcase nuke in a former Soviet-block capitol, or a former tactical US nuke in a US city, or some other country's nuke in a rival country, so that if it were found or detonated there would be confusion. I would give it 75% probability, increasing over time. How many tons of contraband enter the US every year? Why couldn't one 50 kilo package be a nuke? The attacker might set off several in a country as demonstrations, and promise to continue until the country's policy changed in some desired way, when the target country does not know how many there are or what the next target is. It worked nicely against Japan in 1945, when in fact the US did not have a third atomic bomb to drop, and Japan was all set to do house to house fighting at a cost of millions of Japanese lives against a conventional invasion. Edison (talk) 01:34, 5 October 2010 (UTC)[reply]

Now we're talking! :D Thanks, Edison. WikiDao ☯ (talk) 01:50, 5 October 2010 (UTC)[reply]

I think a big difference between ordinary contraband and nuclear weapons is by and large if most contraband gets caught it's annoying but often just a cost of doing business for the people involved. To use the most obvious example, illegal drugs. Whether precursors or finished products most of the high up people accept they're going to lose their packages some times. It's potentially bad for the lower down people involved but for the high up people they know a few discoveries aren't going to affect them in the short term (over the long term people the authorities may work their way up the chain using the leverage garned from things like failed smuggling attempts), they're naturally insulated from that sort of thing. In fact particular with precursors that are cheaply and easily available in other countries a scatter gun approach is sometimes the strategy adopted [18]. This is vastly difference for smuggling nukes since one discovery is enough to cause major problems when it comes to state actors. I'm not saying it will lead to war, but I definitely think the willingness of state actors to risk discovery of nuclear weapons they sent to another country is much, much less then the willigness of most smugglers to risk discovery of whatever it is they happened to be smuggling. And frankly many smugglers (particularly the lower down people and lone gun types) are generally a bit dumb anyway and don't really appreciate the risk to them. Nil Einne (talk) 06:23, 5 October 2010 (UTC)[reply]

But the key thing with the nukes is that once they are in place, it becomes straight-up deterrence. Nasty brinkmanship, to be sure, but I'm not sure I see the difference between that and the Pershing II situation. (For those who are not aware: Pershing II missiles were intermediate range missiles that the US put in Europe, aimed at the USSR. They were a "decapitation" weapon that would totally obliterate the Soviet high command in a matter of minutes. They gave the Soviets a response time to an attack that could be counted in seconds. They made the Soviets very unhappy and very jittery. It was like having a nuclear gun pointed at their head that they would have almost no time to respond to. That's the comparison I'm making to the nuke-in-the-attic = no response time, no defense.) I don't think they'd need to use smugglers to get a nuke in — you could do it through diplomatic pouch if the goal was to keep it in the embassy. The US was actually very afraid of this possibility in the 1950s. --Mr.98 (talk) 12:12, 5 October 2010 (UTC)[reply]

Small point — the US would have had another bomb at the end of the month in August 1945. They would have had roughly a bomb per month after that as well. If the war had dragged on, they would have used them. It was a short term bluff but not a long term one. --Mr.98 (talk) 12:12, 5 October 2010 (UTC)[reply]

In this picture of Mars, what are the things in the foreground that look like bricks? Part of the probe?? Bubba73 ^{You talkin' to me?} 04:09, 4 October 2010 (UTC)[reply]

Look like solar panels to me. So, yes, part of the probe. Dismas|^(talk) 04:13, 4 October 2010 (UTC)[reply]

Yep, see this image from the Opportunity rover article. Dismas|^(talk) 04:16, 4 October 2010 (UTC)[reply]

Resolved

thanks Bubba73 ^{You talkin' to me?} 04:44, 4 October 2010 (UTC)[reply]

Also, note that the image is distorted from its "true" shape because it is a stitched panorama. We also have a section on panorama stitch projection geometry. Because the spacecraft's frame is at the bottom portion of the image and is in the near field of the camera, it suffers from severe geometric distortion when merged to a single panorama image. Nimur (talk) 19:55, 4 October 2010 (UTC)[reply]

The other day I got to see some jellyfish up close. They had some air bubbles in their top part. Why is this? Do they take in some air to adjust some buoyancy? Bubba73 ^{You talkin' to me?} 05:27, 4 October 2010 (UTC)[reply]

Are you sure it was air? Ariel. (talk) 08:11, 4 October 2010 (UTC)[reply]

It sure looked like bubbles of some sort of gas. I got a good look, but I didn't have my camera. Bubba73 ^{You talkin' to me?} 14:36, 4 October 2010 (UTC)[reply]

I saw bubbles in a dead jellyfish on the beach, and assumed it to be outgassing from decay. --Sean 14:39, 4 October 2010 (UTC)[reply]

These were alive. There is a "CoastFest" here each year, and they had them. If they have them again next year maybe I can get a photo. Bubba73 ^{You talkin' to me?} 14:45, 4 October 2010 (UTC)[reply]

Here is an interesting blurb about Jellyfish Lake: "SCUBA is prohibited because the air bubbles exhaled by divers can become trapped in tissue pockets of the jellyfish, air-lifting them to and pinning them against the surface, until the trapped bubbles eventually force their way through the delicate tissue, leaving a nasty wound." --Sean 16:36, 4 October 2010 (UTC)[reply]

Any jellyfish on the beach comes up through the surf... Wnt (talk) 17:24, 4 October 2010 (UTC)[reply]

These jellyfish were captured the day before, so perhaps they were out of the air long enough to get some of it in. Still, I would like to know more. Bubba73 ^{You talkin' to me?} 18:38, 4 October 2010 (UTC)[reply]

Was the jelly fish anything like the one seen in the article Portuguese Man o' War? The bubble is their for flotation. 67.78.137.62 (talk) 18:45, 4 October 2010 (UTC)[reply]

No, they were much smaller and didn't have the tentacles, more like File:Moon jelly - adult (rev2).jpg and File:Palau stingless jellyfish.jpg. But if that one has bubbles, then maybe these do too. Bubba73 ^{You talkin' to me?} 18:56, 4 October 2010 (UTC)[reply]

Today for some reason I decided to invent a new kind of discrimination. According to one study, "latent" toxoplasmosis infection is associated with a 2.5-fold increased risk of traffic accidents[19] - a bit less than the 3.2-fold increased risk for a blood alcohol level of 0.08.[20] As detailed in the article, infection has been tentatively blamed for various psychological situations.

Now one of the most bizarre forms of discrimination in the world occurs in Japan (see Blood types in Japanese culture), where type A is dubbed "fastidious" and type B "wild" etc. Now one study put the toxoplasmosis exposure rate there in 1987 at 28% in males, 16% in females, associated with consumption of raw meat.[21] Relevance? Well, there are reports of blood type B being associated with toxoplasmosis infection [22]; we also have some references to Rh negative or to a lesser degree Rh homozygous positive being more vulnerable to effects on reaction time (see Rh blood group system). So perhaps there's actually a certain grain of truth to this preposterous pseudo-science, though it's not exactly a proved point.

The meat of the matter is really, what is the ethical thing to do? The first publication talks about a million people dying in traffic accidents because of toxoplasmosis infection. Can you justify discrimination against them? Do you talk about increasing the role of treatment, if treatment helps? Is it a public health issue or a private matter? Then there is the effect on pregnancy. And despite decades of teaching that people with HIV aren't dangerous, some of them are infected with high titers of this... there's a can of worms for you. Anyway, I thought I'd throw this up for discussion and see what comes out. Wnt (talk) 07:51, 4 October 2010 (UTC)[reply]

In the intro at the top it says:The reference desk does not answer requests for opinions or predictions about future events. Do not start a debate; please seek an internet forum instead.--Aspro (talk) 09:32, 4 October 2010 (UTC)[reply]

hmmm, I was thinking of this more as an ethics question. Wnt (talk) 16:01, 4 October 2010 (UTC)[reply]

Fascinating tidbit on toxoplasmosis and car accidents. Is it ethical for insurance companies to charge more to insure 16 year old males than 40 year old females? Your toxo example just seems like a specific case, nothing makes it much different than discrimination based on diabetes, heart disease, etc. The public health / private concern issue interesting, but it extends to much more than just toxo status.SemanticMantis (talk) 18:47, 4 October 2010 (UTC)[reply]

I'm just wondering whether there is a risk, when planning genetic experiments based on information gained from genomic databases, that the sequence in your particular cell-line(s) or animal strains varies from the sequence in the database. Is it not prudent to sequence your cell-lines or animals for the region of interest first? I think it is but don't want to risk making a tit of myself by suggesting it to my supervisor if I'm wrong. --129.215.5.255 (talk) 11:09, 4 October 2010 (UTC)[reply]

It depends entirely on what experiment you are doing. If you are working with human cells, you should assume that your cell line of interest will not be identical to the "reference genome sequence" (which is really just a patchwork of several different individuals). However, that may not matter at all. If you are working with an inbred mouse strain, there may be slight differences in your particular sub-line of the inbred strain, but chances are it will be exceedingly close to the reference genome for that strain, since by definition mice from an inbred strain are homozygous at every position of the genome and identical to each other. We might be able to give a more specific answer if we know the specifics of your experimental set-up. --- Medical geneticist (talk) 12:26, 4 October 2010 (UTC)[reply]

If you disrupt a gene by inserting another gene into it and want to use the inserted gene as a marker for the disruption of the original endogenous gene, you could try an IRES. I understand that idea reasonably well. What I don't understand quite so well is the idea of using "splice acceptor" sites, either side of the inserted gene. Would they not just lead to the splicing-out of your marker message, stopping it from being expressed as protein and rendering it useless? Or is the idea that the original gene's message is spliced out, leaving the marker's message to be translated? But this would only work if the endogenous gene had corresponding splice acceptor and donator sites, right? If the "endogenous" gene was actually a stably-inserted GFP gene, it wouldn't have any such sites, making the strategy flawed, right? 129.215.47.59 (talk) 13:45, 4 October 2010 (UTC)[reply]

We'd need more detail about your construct and target. From the talk of IRES and splice acceptors I assume you're describing a more or less random scheme for inserting the marker rather than a knockout by homologous recombination. So the construct may be designed to work under a variety of contingencies, with some features unnecessary in some situations. If it lands 5' to the coding sequence, you don't need an IRES and a 5' splice acceptor should be ignored, and translation begins with your marker. If it lands in an exon midway in the gene, it needs stop codons and then an IRES to (partially) knock out the gene and express the marker, but it doesn't need a 5' splice acceptor. If it lands in an intron midway in the gene, it needs a strong splice acceptor to hopefully divert the mRNA into your construct, then it needs a stop codon, then it needs an IRES. If it lands in a 5' intron, it needs a strong splice acceptor, but the IRES isn't necessary because it's the first methionine the ribosome sees. If I understand you right, that is... Wnt (talk) 16:41, 4 October 2010 (UTC)[reply]

Sorry for not specifying, but the idea was indeed to use homologous recombination, so the location of the disruption would be controlled. The target gene is GFP which was inserted earlier so there are no introns. Doesn't a splice acceptor require a splice donor to function? 178.98.12.16 (talk) 19:12, 4 October 2010 (UTC)[reply]

I'd assume so.... though there could easily be something I didn't think of. For example, there are genes contained entirely within other genes, and perhaps the right splice acceptor could work with a surrounding functional gene. I have to say, I'm surprised to hear of someone going through all the trouble of a knockout in order to disrupt a GFP transgene — so surprised I could be way off base here. Wnt (talk) 02:19, 5 October 2010 (UTC)[reply]

Do we not have an article on the history of automotive electrical systems? I want to know why six volts used to be the standard and why things got changed to twelve. Also why the systems went from positive ground to negative. 155.42.86.171 (talk) 14:36, 4 October 2010 (UTC)[reply]

Nothing in car battery, starter motor, or any "auto* elec*" article:( DMacks (talk) 14:40, 4 October 2010 (UTC)[reply]

Our automotive battery article says: "In the past some cars had 'positive ground'. Such vehicles were found to suffer worse body corrosion and, sometimes, blocked radiators due to deposition of metal sludge.", but with no citation. I don't know about the 6V vs. 12V question. Bigger is better? --Sean 14:42, 4 October 2010 (UTC)[reply]

That is a bit of an oversight. Cars with 6 volt do get passing mentioned in the Jump start (vehicle). I don't know of any cars built after the war that still had six volts but I dare say there may have been some Soviet and Asian made cars still being built. Its asking a bit much for an electic 6 volt starter motor to turn automobile engines as they got larger in size and many budget cars did not have starter motors at all. The amount of copper needed for the leads and windings would have also added to the overall cost. Old aircraft had magnetos for energising their ignition systems and hand swung starting only, so there is no reason why they did not have 6 volts as well..--Aspro (talk) 17:54, 4 October 2010 (UTC)[reply]

Didn't some volvos have 24-volt electrics? -- Q Chris (talk) 14:59, 4 October 2010 (UTC)[reply]

I suspect that in the early days of motor vehicles with small engines (by modern standards) the optimum was the 6V battery and 6V generator (or dynamo). With the progression to larger engines, the advent of diodes for current rectification and therefore use of alternators rather than generators, the optimum was a larger 12V battery (twice as many cells as a 6V) and 12V alternators and starter motors. (Alternators are more robust than generators with their commutator systems, so alternators can turn at faster speeds than generators, producing higher output voltage without the need for more copper.)

The Volkswagen Beetle was manufactured with the 6V electrical system until about the early 1970s. These days, many vehicles with even larger engines, such as trucks, have 24V systems reinforcing the notion that the heavier the engine and the greater the demand for electrical services such as headlights, the more the optimum system progresses towards higher voltage. Dolphin (t) 21:54, 4 October 2010 (UTC)[reply]

I actually owned a 6V Volkswagen back in the 1970s. For whatever reason, it was quite easy to run down the battery, especially in cold weather, and I developed a habit of parking on hills whenever I had the chance. Looie496 (talk) 22:21, 4 October 2010 (UTC)[reply]

A 6 volt battery was adequate to crank the starter for a small engine and to run the headlights and taillight. A 6 volt battery was basically cheaper to manufacture because it only needed three (versus six) lead acid cells. Later batteries also had to run a fan for the heater or air conditioner and more lights, as well as a loud ghetto-blasting sound system. Edison (talk) 01:29, 5 October 2010 (UTC)[reply]

A number of us have written about smaller and larger engines. I suspect that compression ratio is more significant than engine power. Older engines operated on low-octane fuel. They had low compression ratio engines, some even with a hand crank for manual starting when things got tough — great if there isn't a convenient hill around. Modern engines use higher octane fuel and have higher compression ratios requiring more cranking effort to start. Dolphin (t) 01:41, 5 October 2010 (UTC)[reply]

I remember the 6-volt VW. In the early 70s I was jumping one off with my 12-volt Pontiac. I didn't know about the 6V. I clamped down the jumper cables, and smoke started coming out! My car seemed to have electical problems after that. Bubba73 ^{You talkin' to me?} 01:46, 5 October 2010 (UTC)[reply]

Scientifically, what are the odds that Apple's touch devices, like the iPhone, iPod touch, and iPad, are just hoaxes and do not exist in any working form in the supposed form factor and with the supposed method of interaction? (That any photo or video of someone using one must be computer generated, or photo/video edited, or really just taken of someone pretending to use a simple plastic prop like an actor on the set of star trek in the nineties?)93.186.31.238 (talk) 15:02, 4 October 2010 (UTC)[reply]

The odds are greater than 59million to 1 against for the iPhone alone. There are about 59million iPhones identified as being sold. So, at least one person touched the iPhone and was willing to pay for it (so it must be real). Then, you have one guy who claims (without having first-hand knowledge of the device) that it is not real. So, the claim is that each of those 59million sales is a hoax and all of the millions of people involved in purchasing, setting up, and using the iPhone are part of the hoax. Not only part of it, but they are spending their own money to become part of the hoax. Further, not a single person has exposed the hoax. -- kainaw™ 15:19, 4 October 2010 (UTC)[reply]

There wouldn't need to be 59million plants. I doubt anyone is going around counting iPhone users. APL (talk) 15:49, 4 October 2010 (UTC)[reply]

You might as well assert that reality is all a dream and we're all figments of your imagination. There's no way to calculate "odds" on something like that. Either the entire world as you know it is a big lie for really no purpose other than to deceive you (because presumably everyone who owns these things has to be in on the hoax), or it's not a hoax. --Mr.98 (talk) 15:43, 4 October 2010 (UTC)[reply]

You could easily verify the reality of the iPhone products by walking into your local Apple store and asking if you could try one. (I've seen several of them myself, but, of course, I could be lying.)

Until you attempt that experiment, I'm not sure how the odds would be calculated. There's far too many unknown factors. (How much would it cost to hire large numbers of fake users, reviewers, advertising, etc? What is the purpose of the deception? How much is Apple willing to invest? How likely are other groups (Like Consumer Reports, for example) to go along with the hoax?) There's no obvious way to calculate any of these factors.

In a situation like this, a scientist wouldn't really bother with probability, he would concern himself with how to make an experiment that tests the hypothesis. If the scientist goes to the Apple store and is successfully able to purchase a real working iPad, well, then the theory is disproved. Ipads are real.

It becomes far more interesting if the scientist goes to the apple store and it's been closed for some reason, then he drives to the next closest apple store, and that's also mysteriously closed! Now the scientist has some evidence. He doesn't have proof that Apple is a hoax, but he has a weird anomaly. He could figure out the odds that the first two stores he tests are closed by coincidence. Then he could use probability theory to determine the odds that Apple stores are intentionally being closed for some mysterious reason.

That's still a long way off from answering your question, of course. APL (talk) 15:49, 4 October 2010 (UTC)[reply]

P.S. I like to imagine that our hypothetical scientist would perform his "Going to the Apple Store to buy an iPad" experiment while wearing a lab coat and safety goggles. APL (talk) 15:52, 4 October 2010 (UTC)[reply]

S/he would have to complete a 14-page research ethics approval form first.Itsmejudith (talk) 16:01, 4 October 2010 (UTC)[reply]

Am I the only one to find the question funny given who owns the IP the OP is using? Nil Einne (talk) 16:31, 4 October 2010 (UTC)[reply]

HAHA! That is hilarious. APL (talk) 16:42, 4 October 2010 (UTC)[reply]

I think the concept of "odds" does not exist for this question. Odds applies to random events, an iPhone existing, or not existing is not a random event. Ariel. (talk) 19:16, 4 October 2010 (UTC)[reply]

According to Bayesian probability, random just means unknown. It's not as if all the probability laws wouldn't work in a chaotic but deterministic universe. As for figuring it out, I figure the most likely explanation other than those products existing is you hallucinating. I don't know what the probability of that is offhand, and there's always the chance that you just hallucinated the evidence that hallucination is rare, which wouldn't be all that unlikely if hallucination wasn't all that unlikely. — DanielLC 23:28, 4 October 2010 (UTC)[reply]

I believe (INAStatistician) that it's meaningless to calculate odds without some set of underlying assumptions (then you add in your defined unknowns). Given the depth of a conspiracy required to create the illusion of iP{hone,ad,od}s existing, there's not a whole lot you can rely on if they don't. We're brains in vats overseen by reptilian humanoids which were created by HAARP? Sure, we can throw that in. Paul (Stansifer) 23:56, 4 October 2010 (UTC)[reply]

(edit conflict) Apparently, there is maybe about a 1/3 chance of something like that being the case, Paul. Apologies for trotting this paper out again for a third time around here now, but see [23]. WikiDao ☯ (talk) 02:25, 5 October 2010 (UTC)[reply]

If you're a Bayesian statistician, then you need to assign some sort of Prior probability before you can do a study to better refine your probability. I suppose you could look at how many other, similar electronic devices have turned out to be complete hoaxes. I'm not sure what sort of data you would collect to refine your distribution though... Maybe go to an Apple store, as APL suggested. I Am Not A Statistition either, but it does bring up some interesting statistical points. How is it appropriate to come up with prior probabilities? Is it appropriate at all to try to assign prior probabilities in all cases? These are questions that are routinely debated in the statistics departments of major universities, and while this question is trivial (in my opinion), it does provoke deeper thought about the proper way to do statistics. Buddy431 (talk) 02:23, 5 October 2010 (UTC)[reply]

my soil contains a ph of 8.3 .which plant is suitable to grow in my soil? —Preceding unsigned comment added by 117.254.150.111 (talk) 15:44, 4 October 2010 (UTC)[reply]

It contains a ph? Why don't you just remove the ph? :) 129.215.5.255 (talk) 15:47, 4 October 2010 (UTC)[reply]

Please don't make fun of poster's grammar. First, may posters are not native English speakers, and second, it's rude regardless. APL (talk) 15:59, 4 October 2010 (UTC)[reply]

(edit conflict)Hey 129.215: There's no need to berate people for their grammar errors. To 117.254: The articles Soil pH and Alkali soils have some background. Depending on where you live, large "home centers" or "gardening centers" like Home Depot often sell treatments to correct soil pH problems. --Jayron32 16:01, 4 October 2010 (UTC)[reply]

It would help to know were you live. If the pH is high because you live in the desert will require different plants to if you live on chalky soil in some cold climate. 8.3 is also a bit high, could it be due to ash or some other contaminate being disposed there?--Aspro (talk) 16:20, 4 October 2010 (UTC)[reply]

I'll berate Jayron32's grammar by saying that berate is not the most accurate word when a little emoticon was added to the comment. --Chemicalinterest (talk) 16:51, 4 October 2010 (UTC)[reply]

High ph means that plants struggle to absorb essential elements such as iron, manganese, zinc and phosphorus. You are likely to get yellowing of the leaves of most plants. Adding aluminum sulphate or peat moss or manure or just plain sulphur is often recommended to lower the ph. Vegetables such as spinach, asparagus, carrots, cabbage and celery can tolerate ph up to 8 or so. Meadow flowers can often cope with high ph, but I don't know of many garden plants that can cope with 8.3. Is all of your soil such a high ph? Has someone been dumping lime on the soil? Dbfirs 17:00, 4 October 2010 (UTC)[reply]

For what it's worth, the OP's IP number geo-locates to New Delhi. Where about in India are you? Do you want native plants? Do you get bad monsoons? CS Miller (talk) 18:27, 4 October 2010 (UTC)[reply]

Then it is probably just something known a canker (Kanker) which frequently forms naturally in hot dry climates (well, hotter than the one I live in) which lie in a alkaline soil area. The colder Chilean potash mines might be an exception... but then again, they were laid down along time ago and they might have been nearer to the equator then. Yeah, forget I mentioned that. Think that the inquirer would be better off seeking out a New Delhi horticultural organisation for a list of plants (herbs/flowers/food crops/fruit trees etc.) that favours local conditions. Also, green manure, dug back in, will ferment and so produce CO2 that will help to acidify the soil and improve its structure, enabling a greater range of horticultural options to choose from. Our article Alkali soils has a fuller explanation. A local New Delhi organization will be able to provide much better advice that we can here, because the OP is living in a small local area of alkaline soil were he would benefit more from local know-how.--Aspro (talk) 21:22, 4 October 2010 (UTC)[reply]

I have no reason to question the OP:s ph-value but be aware that some cheep ph-meters are rather inacurate. I has one that can be of by more than one unit. --Gr8xoz (talk) 21:40, 4 October 2010 (UTC)[reply]

Our small storage refrigerator broke recently and some meat inside it rotted. Now the whole thing stinks. What is the best way to deodorize the refrigerator compartment? Note: There was only meat, milk, and water jugs in the refrigerator. There was no food that needed to be saved. Thanks, Chemicalinterest (talk) 15:46, 4 October 2010 (UTC)[reply]

I've noticed sliced lemon used to deodorise a fridge. Otherwise, you can get a spray product that is a combination of Flash(tm) and Febreeze(tm) which might do the trick. --129.215.5.255 (talk) 15:49, 4 October 2010 (UTC)[reply]

Two common substances to deodorize a fridge are activated charcoal and baking soda. There are a multitude of little containers which you can hang in the fridge to get the smell out. Or, you can just spread some baking soda on a dish and see if that does the trick. It may take a few days to see if it works, depending on the severity of the stench. --Jayron32 15:58, 4 October 2010 (UTC)[reply]

(editconflict) Bicarbonate of soda is traditionally used to clean fridges and I think it could deodorise it to an extent. Itsmejudith (talk) 15:59, 4 October 2010 (UTC)[reply]

Check under the fridge as well (in the drain pan). It is possible that some stinkyness got in there. -- kainaw™ 16:11, 4 October 2010 (UTC)[reply]

Peroxide bleach for the first thorough clean. Plenty of baking soda (half a cup) and water for the next wash. Air it, to let the odours disperse. Don't expect miracles over just one night. Put a bowl of backing soda and water inside to continue to absorbers the smell. Finally get one of the charcoal fridge absorbers.--Aspro (talk) 16:14, 4 October 2010 (UTC)[reply]

My experience is that the metal in the fridge is quite easy to deodorize; any of the washing mechanisms noted above will work. The problems lie in the plastic bit: racks, bins and door liners. If the smell persists beyond all your best effort, you might need to replace these elements. Bielle (talk) 16:21, 4 October 2010 (UTC)[reply]

I used hypochlorite bleach and will see whether that works. We did drain the drainpan. It is mostly plastic. Thanks for the suggestions. --Chemicalinterest (talk) 16:50, 4 October 2010 (UTC)[reply]

There was a similar question here: Wikipedia:Reference desk/Archives/Science/2010 June 28#Getting rid of freezer odour. Ariel. (talk) 20:05, 4 October 2010 (UTC)[reply]

Vanilla essence has worked for me in the past. There are even commercially available products containing it if you want to spend the money, but raiding your pantry is cheaper. Just put some on a damp cloth and wipe all the surfaces. Certainly a lot more food friendly than hypochlorite! Mattopaedia ^{Say G'Day!} 10:36, 5 October 2010 (UTC)[reply]

I have a bunch of lithium cr2032 Button cell batteries for a project, they are in packaging that is overly secure, a pain in the ass to get open, and then not at all secure once opened. I want to repackage them so that they are easier to access. My worry is that I should not dump them all into a tupperware container or a plastic bag, as they might overheat when the terminals are touching in a big group. Is this a valid fear? Any ideas on an easy way to keep 300 of them separate? Beach drifter (talk) 18:34, 4 October 2010 (UTC)[reply]

Just curious. What use do you have for 300 Cr2032 batteries.(I just use a good pair of beefy scissors)--Aspro (talk) 18:48, 4 October 2010 (UTC)[reply]

This + This. Beach drifter (talk) 19:03, 4 October 2010 (UTC)[reply]

Parafilm? Wnt (talk) 18:49, 4 October 2010 (UTC)[reply]

Yes it's a valid fear. Take a long piece of tape and stick each one on it. Stick it negative side (the "inner" metal side) down. I would use packing tape and do two rows. Regular scotch tape will probably not be strong enough. Ariel. (talk) 19:22, 4 October 2010 (UTC)[reply]

I would take a long sheet of plastic wrap. Cover one half of it with batteries, leaving about 1/4 inch of space between each battery. Fold the other half of plastic wrap over the batteries. Fold up the sandwich and shove it in a box. --Chemicalinterest (talk) 20:08, 4 October 2010 (UTC)[reply]

DO NOT stack them in a tube or a similar configuration without insulating spacers. This was my first idea that pooped up in my head but the next second I realized that the voltage end to end would be 900V!!! --Gr8xoz (talk) 20:47, 4 October 2010 (UTC)[reply]

Yes, that would be so much voltage, although the stack will be 96 cm long. Did you know the first two numbers on a battery indicate its diameter in mm. So CR2032 are 20 mm. The 32 stands for how many 1/10mm it is thick. So it is 3.2 mm thick. --Chemicalinterest (talk) 23:05, 4 October 2010 (UTC)[reply]

If the earth's velocity through space is not constant then doesn't that imply that time as we perceive it is not consistent throughout our lifetime? Or if the earth increases (via radiation from the sun and meteorites) or decreases (via sending probes and satellites into space) in mass then doesn't that also affect how we perceive time? So one minute when I was 3 could vary in length from one minute when I was 25? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:55, 4 October 2010 (UTC)[reply]

How would you know? You can only measure time by comparing to something else. But yes, if mass changes, time does too. Speed does it too, but in a more complicated way. Ariel. (talk) 20:06, 4 October 2010 (UTC)[reply]

No, a minute is by definition a unit of time so, by definition, two minute long events have the same duration regardless to where in the universe you happen to be. 67.78.137.62 (talk) 20:07, 4 October 2010 (UTC)[reply]

I do not think it is that simple, there are two aspects of this:

Previously seconds and minutes was defined in terms of the rotation and orbit of earth, depending on the timescale used compensations for this is still introduced, e.g. leap seconds (61 s in some minutes).

Relativistic effects, if the earth change speed or mass the time on earth will get an other “speed” relative to the rest of the universe. The local “length” of one minute on earth is still exactly the same and all processes is affected in the same way.

--Gr8xoz (talk) 20:40, 4 October 2010 (UTC)[reply]

Time is relative. —Preceding unsigned comment added by 165.212.189.187 (talk) 20:18, 4 October 2010 (UTC)[reply]

Yes, time ir relative, but a minute is a minute is a minute. Here's an analogy: Two runers are coming down a curve on the road. The outside runner has a longer distance to go to the final line than the inside runner just because he is on the outside track. Distance is relative! And yet, a meter is still a meter. 67.78.137.62 (talk) 20:35, 4 October 2010 (UTC)[reply]

That is a bad analogy. A minute measured inside Earth's gravity well will not be the same duration as a minute measured outside of Earth's gravity. If you're standing next to the earthbound clock you will observe that the spacebound clock is running too fast. If you're standingfloating next to the spacebound clock you will observe the earthbound clock running too slowly.

I am 67.78.137.62 above. I am a physics professor and know all about relative time. The problem is not with my answer, but instead with the question asked. The length of a minute doesn't get any longer or shorter. Read my analogy again and see if you understand it this time. It is quite instructive. 174.58.107.143 (talk) 04:34, 5 October 2010 (UTC)[reply]

I agree, it's a good (and close) analogy. The elapsed time as measured by your wristwatch (which is also the rate at which you think, age, etc.) is the length of your worldline in spacetime. If you only care about clocks that are near Earth's surface then it doesn't matter how Earth is moving relative to the rest of the universe, for the same reason that if you only care about the relative distance traveled by the runners, it doesn't matter how the track is oriented relative to the north pole or the Moon. Though Earth's motion doesn't matter, its rotation (around its own axis) does, because a helical curve is longer than a straight line pointing in the same direction. Gravitational effects can be included in the analogy too. If you imagine that the race course is extremely long and both tracks run east-west, the runner farther from the equator will have less distance to travel; that's (closely) analogous to gravitational time dilation. Furthermore, if the runners ignore the tracks and run in a straight line (great circle), they will veer toward the equator. That's analogous to the gravitational force. -- BenRG (talk) 07:27, 5 October 2010 (UTC)[reply]

Similarly, if you were floating in space watching clocks on earth, you would observe that time is running slower on Earth now than it did twenty-two years ago. (That is to say that the minutes appear longer.) This is because the Earth has gotten heavier.

(For those of us stuck here on Earth for the whole time, there is no observable change, because we slow down just as much as our clocks do.

All of these effects are incredibly tiny because the Earth just isn't heavy enough to cause really dramatic time dilation.

Here is an article Gravitational_time_dilation. APL (talk) 20:44, 4 October 2010 (UTC)[reply]

Another thing to check out: Twin paradox. --- cymru lass ^{(hit me up)}⁄_{(background check)} 23:46, 4 October 2010 (UTC)[reply]

The difference in the passage of time between years is too small to be of any effect with current measuring technology. On the other hand, the change in "clock speed" over any given year is significant: basically, if you think of someone floating in space way above the Solar System and observing clocks on Earth then, to the space observer, Earth clocks run slowest in January and fastest in June. This is because the Earth is closest to the Sun, and moving fastest along its orbit, in January. Physchim62 (talk) 02:04, 5 October 2010 (UTC)[reply]

Let's say Jupiter is right above, like, you can fly directly at it, so it will take you one year to get there. How fast would you have to go to get there? In miles per hour, preferably. Thank you!--Editor510 ^{drop us a line, mate} 20:46, 4 October 2010 (UTC)[reply]

I assume that you're postulating that Jupiter and Earth are in alignment relative to the Sun, so that the distance between the two is the difference between the average orbital radii, and that you're looking for an average speed? If so, the orbital information may be found at Jupiter and Earth (semi-major axis is what you want), and you can do the math from there. Acroterion _(talk) 20:53, 4 October 2010 (UTC)[reply]

I got roughly 20km/sec, which is roughly equal to 45,000 mph. I could not tell you when the window for that trip would be though. Googlemeister (talk) 20:56, 4 October 2010 (UTC)[reply]

(edit conflict) It's a bit trickier than that, since Jupiter is moving, so you need to aim for where it is going to be in one year, and arrive at that time. Aiming for the average distance from the sun between Jupiter and Earth is meaningless, since, depending on the time of year for each planet, you could be off by a factor of two or more. You need to know a) what day you plan to leave Earth and b) where Jupiter will be when you get there. Simply aiming for Jupiter's orbit means that you may sit around and wait for several years before Jupiter comes by and picks you up, a very inefficient way of doing it. It would probably take a bit of calculus (simple calculus, but calculus none the less) to calculate the travel time between two co-moving bodies. --Jayron32 20:59, 4 October 2010 (UTC)[reply]

Oh no, it's for a hard science fiction story, so, I think Googlemeister's answer handles everything.

Resolved

--Editor510 ^{drop us a line, mate} 21:01, 4 October 2010 (UTC)[reply]

If it is a true hard science fiction story i think you want a more realistic mission profile, to travel in a straight line at constant speed is ridiculously inefficient since you will need to compensate for the suns gravity, and the speed of the earth and then you need to match the speed of Jupiter. A god place to get this type of info is [24], in this case the sub-pages [25] and [26] are relevant. --Gr8xoz (talk) 21:29, 4 October 2010 (UTC)[reply]

For hard hard SF, see Hohmann transfer orbit. --Stephan Schulz (talk) 21:36, 4 October 2010 (UTC)[reply]

And consider whether your space-program would prefer a Hohmann orbit, or a minimum energy transfer orbit, or some other orbit profile. The most practical orbit is an engineering tradeoff; it has to do with how long you want to provide life support; how much radiation shielding you want to provide for the astronauts; whether you can afford to put a lot of mass into low-earth-orbit; how the mass (i.e., fuel) is expended throughout the orbit profile. For example, if you want to reach Jupiter in a hurry, you arrive at the planet traveling very fast. Then you must spend a lot of fuel to slow down ("capture"). So this means you have to carry a lot of fuel with you, i.e. a larger spacecraft - which exponentially increases the mass you had to take to low-earth orbit. On the other hand, you can design a "direct descent" orbit scheduled to arrive at Jupiter with zero velocity relative to the planet; but it will take dramatically longer to arrive, and your engineering burden is much harder (because you have fewer opportunities for trajectory correction maneuvers if you aren't carrying fuel with you). Such engineering tradeoffs are easy to work out in science fiction, because you don't have to worry about a budget. Nimur (talk) 22:30, 4 October 2010 (UTC)[reply]

(5-1)AU * 93e6 miles/AU / 365.24 days/year / 24 hours/day = 42 438 miles/hour, AU is the Astronomical Unit, the distance from sun to earth, Jupiter is as closest 5 AU from the sun. This asumes that you move in a stright line and time it so you arive at the same time as jupiter. ofcurse this is not a realistic way to travle to jupiter. —Preceding unsigned comment added by Gr8xoz (talk • contribs) 21:04, 4 October 2010 (UTC)[reply]

Thank you, but, as you can see, I posted a {{resolved}} meaning I got the answer I wanted. No mission profile is needed, but I appreciate the help. :)--Editor510 ^{drop us a line, mate} 21:38, 4 October 2010 (UTC)[reply]

Is there a way to derive E=mc² without integral calculus? 74.15.136.172 (talk) 00:02, 5 October 2010 (UTC)[reply]

Well, the original derivation required no calculus (just some clever algebra), I'm fairly sure: [27] --Mr.98 (talk) 00:15, 5 October 2010 (UTC)[reply]

By dimensional analysis, any high school student with a basic knowledge of algebra and of physics should be able to determine that the units of measurement require the E=mc² equation, perhaps with some proportionality constant multiplied by side of the equation. What are the units of energy? Kilogram meters squared per second squared. What are the units of mass? Kilograms. What are the units of c²? Meters squared per second squared. Then see if any other power would allow the equation to balance. For instance, if I asserted that "E=mc" you could easily prove me wrong, the same as if I asserted that "E² =mc" or that "E⁷=m⁴c³. Outside the Einstein equation, you would be required to assert that "meters = meters cubed " or some such obvious nonsense. Edison (talk) 01:19, 5 October 2010 (UTC)[reply]

Dimensional analysis tells one that a mass multiplied by a velocity squared gives a result that has the same base units as an energy unit, but I would hesitate to call that any sort of 'derivation'. (Consider that atomotive fuel efficiency is often cited in liters per 100 km — volume per length, which is dimensionally equivalent to an area. Nevertheless, it wouldn't make intuitive or physical sense to describe one's mileage in units of square meters.) It's possible to determine that E=mc² contains all the terms to the correct order to give energy, but that's a very thin explanation, and it doesn't tell us why no other physical constants or measurements don't play a role. For example, E = Gm²/l, where l is the length of the object, m is its mass, and G is the gravitational constant also gives the correct units, but is a totally meaningless formula. TenOfAllTrades(talk) 02:51, 5 October 2010 (UTC)[reply]

While the rest of your comment is spot on, it is both intuitive and physically meaningful to speak of fuel consumption in terms of area (or fuel efficiency in terms of inverse area). The area is the cross section of fuel needed to travel a given distance, if that volume of fuel is stretched out over that distance. So if my tractor consumes 1 l / km = 1 mm^2, then it could travel indefinitely were it fed by a prepositioned fuel supply of 1 mm^2 cross sectional area along the route traveled. -- ToE^T 10:32, 5 October 2010 (UTC)[reply]

In the article the guy above linked to, how did the equation l' = l(1 - (v/c)cosθ)/sqrt(1 - (v/c)²) come about? 74.15.136.172 (talk) 02:57, 5 October 2010 (UTC)[reply]

That first equation is just the Lorentz transformation of the photon energy, where the Lorentz boost is at an angle to the photon momentum. You can see a Lorentz boost in a general direction at the bottom of this section. 129.234.53.175 (talk) 14:57, 5 October 2010 (UTC)[reply]

I didn't understand half of the above; but I did enjoy Brian Cox's Why Does E=mc²?[28] Bazza (talk) 14:49, 5 October 2010 (UTC)[reply]

There is no real rigorous derivation of E = m c^2. You have to ask yourself from what theory you want to derive this from? Obviously, any rigorous derivation has to start from the postulates of special relativity, but then the derivation is trivial. Rather what passes for a derivaton of E = m c^2, is a heuristic arguments for the correct equation. Einstein's argument makes electromagnetism compatible with mechanics, but then electromagnetism is obviously already a relativistic phenomena. A rigorous agument obviously would not be allowed to invoke the properties of electromagnetic radiation!

Einstein later gave a similar argument (I think in 1936), which is far simpler. Suppose you have two objects of mass M floating in space, a distance L apart at rest w.r.t. each other. No external forces act on the masss. Then one object emits a photon of energy E, which is absorbed by the other mass. The photon as a momentum of E/c, so when one object emits it, it gets a velocity of v = E/(M c). The photon reaches the other object in a time of t = L/c. By that time the object that emitted the photon has moved by a dstance

d = v t = E/(M c) L/c = E L/(M c^2).

So, this suggests that in the original center of mass frame, the center of mass of the two object system will move by a distance d/2. But ths can't be true, because there are no external forces acting on the two objects. The exchange of the photon happened within the two object system, so momentum must be conserved. In the original center of mass frame, the momentum must remain zero and the center of mass cannot have moved at all. But the end result is undeniably that just after the photon has been absorbed, one object has moved by a distance d. So, if the center of mass does not move, then the masses must have changed.

If an amount of mass delta m has been exchanged in this process, then that would contribute to a shift in the center of mass of (delta m L)/(2 M) in the opposite direction. This has to compensate for the shift of d/2, so we find that:

delta m = M d/L = E /c^2

Count Iblis (talk) 15:13, 5 October 2010 (UTC)[reply]

Is it possible to obtain a DNA sample from a living person, and another sample later on, of a deceased person, and confirm that the sample is from the same person? Also are you able to tell approximately the time/date of death from a DNA sample? Can DNA show medical conditions such as diabeties or cancer? —Preceding unsigned comment added by Aneelr (talk • contribs) 01:11, 5 October 2010 (UTC)[reply]

Yes, no, no (but DNA could show a tendency toward diabetes or cancer. (I pronounce myself subject to correction on the third answer). Edison (talk) 01:22, 5 October 2010 (UTC)[reply]

DNA can show if you have a Genetic predisposition toward a disease.Smallman12q (talk) 02:01, 5 October 2010 (UTC)[reply]

Certain diseases, like Cystic Fibrosis, are completely determined by DNA. It is pretty trivial to tell whether a person has cystic fibrosis (or more importantly, whether they are capable of passing it on to their offspring) by looking at only a small section of their DNA. Such testing is a common way to determine if a baby has Cystic Fibrosis. Tay-Sachs disease is another such disease. With both of these examples if a person has two recessive copies of a particular gene, they have the disease. If they don't, they don't. There are different tests for each disease, including a genetic test for each. While it is typical to only perform such tests on a living person, I see no reason why it could not be performed on the DNA of a deceased person, provided the DNA had not degraded too much. Buddy431 (talk) 02:13, 5 October 2010 (UTC)[reply]

You might be able to tell if a person has a viral infection, or even certain types of cancer, through a DNA test, but (as I understand it) there's a risk of false negatives – i.e., that the person has the condition but you don't see it – when you are just running a standard DNA test from a single biological sample. So, if you had a sample of breast tissue, you might be able to tell if the woman concerned had breast cancer from a DNA test, although there would be simpler ways of doing it, the DNA test usually comes after you've confirmed cancer by more traditional means. If you could reliably tell that a woman had breast cancer through a DNA test on a blood sample, you would become very rich indeed. Each cancer is distinct in this respect: leukemias, for example, should be much easier to detect by DNA testing on blood than cerebral cancers. Physchim62 (talk) 02:54, 5 October 2010 (UTC)[reply]

After how many year since he first developed the in vitro fertilisation until he got the Nobel prize?174.20.65.111 (talk) 02:21, 5 October 2010 (UTC)[reply]

From our article on Robert G. Edwards, the first in vitro fertilization of a human egg was in 1968 (42 years ago), and the first baby born using the technique was in 1978 (32 years ago). Physchim62 (talk) 02:25, 5 October 2010 (UTC)[reply]

WOW he finally got the Nobel prize after like 40 years. The Nobel prizes reward are too late! Some people may not live that long to receive what they deserve.174.20.65.111 (talk) 03:16, 5 October 2010 (UTC)[reply]

It's particularly impressive in view of the fact that Nobel's will, which set up the prizes, specified that they should be for work done in the past year. But there are good reasons why it was felt that following this rule was inappropriate. See Nobel Prize#Recognition time lag. --Anonymous, 03:25 UTC, October 5, 2010.

Indeed. In this case, Edwards had a coworker called Patrick Steptoe, who was a gynecologist and developed laproscopy to collect the eggs needed for IVF: Steptoe died in 1988, so never received the Nobel Prize that many believe he deserved. Physchim62 (talk) 03:32, 5 October 2010 (UTC)[reply]

Note that the Fields Medal, sometimes referred to as the "Nobel Prize of Mathematics", is only awarded to mathematicians under the age of 40, because "... while it was in recognition of work already done, it was at the same time intended to be an encouragement for further achievement on the part of the recipients ...". As a result, Andrew Wiles did not receive one for his proof of Fermat's Last Theorem, however the IMU did presented him with a plaque which has been referred to as a "quantized Fields Medal". -- 124.157.234.91 (talk) 09:00, 5 October 2010 (UTC)[reply]

Under our kitchen sink we keep a coffee container of old coffee grounds and the juiced parts of fruits and veggies. When I open it u to add to it, I try to breath out of my nose for fear of getting a whiff of foul smelling compost. To my surprise this evening I opened it and got a not so offensive smell up my nose, and, in fact, it smelt good, like a bad-selling flavor of ice cream. What causes this? Thanks Wikipedians! schyler (talk) 02:45, 5 October 2010 (UTC)[reply]

Coffee grounds are a cheap deodorizer. They are known to be used, for example, at perfume counters in stores to "clear the palate", so you can properly smell each perfume and not keep smelling the previous perfumes. It is likely that the coffee smell overwhelms your sense of smell in general, which "clears out" the other smells. this Google search turns up lots of stuff on using coffee in this way. --Jayron32 03:12, 5 October 2010 (UTC)[reply]

If your house is warm enough, the fruits and veggies may have begun fermenting. While I wouldn't call that smell especially pleasant, there is a sickly sweetness to it that might be reacting well to the coffee. Hobo Irish-Cream ice cream, perhaps? Matt Deres (talk) 04:30, 5 October 2010 (UTC)[reply]

Pruno perhaps? --Jayron32 04:33, 5 October 2010 (UTC)[reply]

why does the gravitational constant decrease when we go towards the centre of the earth? —Preceding unsigned comment added by 120.56.189.145 (talk) 07:35, 5 October 2010 (UTC)[reply]

It doesn't. The Gravitational constant is, as its name suggests, a constant (unchanging) value. The actual gravity experienced may however vary, so perhaps you are thinking of that; see Earth's_gravity#Variation_in_gravity_and_apparent_gravity. --jjron (talk) 07:57, 5 October 2010 (UTC)[reply]

Yes. Basically the reason is simply that when you are below ground, some of the Earth is above you, so it is pulling you upwards instead of downwards. --Anonymous, 08:00 UTC, October 5, 2010.

See shell theorem. The outer shell of the earth, above you, does not attract you at all. 157.193.175.207 (talk) 08:00, 5 October 2010 (UTC)[reply]

Re 157.193.175.207 - that would seem to be assuming a hollow sphere (point 2) so not apply; the Earth is obviously not hollow, so would more closely approximate point 3, i.e., "...the gravitational force varies linearly with distance from the centre, becoming zero at the centre of mass." --jjron (talk) 08:27, 5 October 2010 (UTC)[reply]

No, it doesn't assume a hollow sphere. You can write the total force caused by the (full) earth as the force caused by the (full) sphere beneath you (whose mass varies as r^3 and r^3/r^2=r thus linear) + the force caused by the (hollow) shell above you (which is 0). The variation isn't caused by the upper layers attracting you in the opposite direction, it's because the upper layers don't attract you at all, thus only the mass beneath you influences g. 157.193.175.207 (talk) 09:19, 5 October 2010 (UTC)[reply]

Obviously each individual part of the shell does exert a gravitational attraction - gravity isn't switched off. But inside the shell, the attraction due to a specific part of the shell is balanced by an equal and opposite gravitational attraction from another part of the shell. So the net gravitational attraction due to a hollow spherically symmetric shell is zero at any point inside the shell. The rest of the analysis above is fine. Gandalf61 (talk) 11:10, 5 October 2010 (UTC)[reply]

As autumn progresses into winter, we are getting more and more condensation on the interior surfaces of our windows. This led to a serious mold problem in one particular corner last year. I'm a bit at a loss as to how to lower the humidity of our apartment's air without resorting to opening the windows and freezing ourselves. Currently, I'm simply wiping down the windows. That prevents pooling along the sills, but only transfers the moisture to the towels -- it's still in the apartment and when the towel dries the moisture has simply returned to the air. Thus the cycle continues. We don't have an electric clothes dryer, and we have under-floor heating. I suppose I could leave the oven door open... Suggestions? The Masked Booby (talk) 09:24, 5 October 2010 (UTC)[reply]

Dehumidifier? You could pour the water down the sink. Dismas|^(talk) 09:44, 5 October 2010 (UTC)[reply]

Our article on dehumidifiers does not mention the small, cheap, chemical dehumidifiers you can get. These use a sachet of crystals which absorb water from the air. DuncanHill (talk) 09:46, 5 October 2010 (UTC)[reply]

Some form of dehumidifier is definitely the only good option here - in some way, you need to reduce the amount of water vapour in the air. By the sound of the original question, the scale of the problem here may be beyond efficient usage of chemical dehumidifiers, and one of the electrically-powered ones would strike me as a good investment. It may be worth leasing one for a week or two from an equipment hire company, just to see to whether it effectively solves the problem or not - you can then consider buying one. ~ mazca ^talk 10:08, 5 October 2010 (UTC)[reply]

Why would leaving the oven door open help? Your problem is that warm, wet air is hitting the window, which is cold from the cold outside, and water is condensing out. Solutions are: warm the inside of the window (double glazing helps, if you can get it, or directing warm drier air to blow over the window as in a car) and reduce the moisture in the air (you can achieve some of that by turning the heating down, but I'm guessing that would get unpleasant). A cheap, passive dehumidifier using cheap, replacable crystals that dissolve as they absorb the water, may be your best bet, although you may need several large ones scattered in the worst spots. I've also had luck using anti-mould spray (in a well-ventilated room), which then reduced later mould growth. 109.155.37.180 (talk) 09:58, 5 October 2010 (UTC)[reply]

In winter humidity is already pretty low, if you dehumidify on top of that you will have a very unpleasant living experience. Can you read the Dew point article, and estimate what temperature your window is? Look specifically at the section "Calculating the dew point". I think you will find it's impossible to dehumidify your apartment enough. You can lower the temperature of the apartment, or insulate the windows.

My suggestion: Get those plastic window films that cover the entire window (something like this, or just google for "Plastic Window Insulation"). Use that to insulate the window to some degree. Your second option is to give the moisture a place to drain - drill holes in the sill probably. Ariel. (talk) 10:59, 5 October 2010 (UTC)[reply]

I've heard that most infants whose mothers are HIV-positive contract HIV through childbirth, which confuses me. Wouldn't they contract it in utero? During gestation, the mother shares nutrients, etc. with the fetus through the umbilical chord. Isn't it likely that during those 9 months, the child would contract HIV, instead of at childbirth? --- cymru lass ^{(hit me up)}⁄_{(background check)} 14:01, 5 October 2010 (UTC)[reply]

The placenta blocks transmission in utero in most cases, but during passage through the birth canal there is a risk of transmission. --14:10, 5 October 2010 (UTC) —Preceding unsigned comment added by 81.153.109.200 (talk)

This was discussed just above. The placenta blocks the HIV virus from passing in most cases. Regards, --—Cyclonenim | Chat  14:18, 5 October 2010 (UTC)[reply]

Mostly to get new knowledge (I am a retired teacher of math- phys,M.Sc) I am at present reading T. S. Kemp: The Origin and Evolution of Mammals. After that I would like to learn about anapsid and diapsid animals in the Permian —Preceding unsigned comment added by 87.54.145.241 (talk) 14:13, 5 October 2010 (UTC)[reply]

Okay, so what would you like us to do? Find books on anapsid and diapsid animals in the Permian for you? Regards, --—Cyclonenim | Chat  14:19, 5 October 2010 (UTC)[reply]

Wow! You're in a bad mood today! You might prefer to stay off the reference desk for a while if you're just going to bite at people. Physchim62 (talk) 15:40, 5 October 2010 (UTC)[reply]

We have articles on both anapsids and diapsids that should give you a starting point. Mikenorton (talk) 14:26, 5 October 2010 (UTC)[reply]

I think there is a good chance the OP meant to ask about synapsids (the group that includes mammals) rather than anapsids (a group that mainly includes turtles). Looie496 (talk) 14:52, 5 October 2010 (UTC)[reply]

Why is something like this [29] so expensive? I don't think it is anything except a section of tubing, an element, a thermostat and a cut-out, i.e. the same set of components as an electric kettle but more crudely made? I have an existing heater like this but it isn't working. It was always a bit prone to cut out and then difficult to reset, and now it doesn't want to reset at all. Would a competent electrician be able to repair it? Could a DIY enthusiast realistically make one? I don't want simply to order this at the price, but the winter is coming... (We don't seem to have an article on duct heater). Itsmejudith (talk) 15:28, 5 October 2010 (UTC)[reply]