June 21

File:Pretty the flower.jpg. Since the team here are so good at this...This plant started growing in my garden, from the foliage I initially thought it would become a bluebell. It then produced this flower which has finally opened this morning. Does anyone know what it is please? My child has been watering it and has named it "Pretty". Thanks — Preceding unsigned comment added by Anton.Brad (talk • contribs) 10:13, 21 June 2020 (UTC)[reply]

I'm having trouble displaying the picture I uploaded to commons. Any help would be appreciated. Thanks — Preceding unsigned comment added by Anton.Brad (talk • contribs) 10:40, 21 June 2020 (UTC)[reply]

You mean this?[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:56, 21 June 2020 (UTC)[reply]

It's a lily (Lilium), probably an Asiatic hybrid, though there are very many varieties of those. This is the google images page for Asiatic hybrids. PaleCloudedWhite (talk) 11:02, 21 June 2020 (UTC)[reply]
The variety 'Abbeville's Pride' looks similar (especially on the third image down on that link). It is also quite a short variety (your pic looks like a short variety, though the shot angle makes it a bit difficult to gauge). PaleCloudedWhite (talk) 11:17, 21 June 2020 (UTC)[reply]

Thank you very much all. This has been resolved. — Preceding unsigned comment added by Anton.Brad (talk • contribs) 11:39, 21 June 2020 (UTC)[reply]

The Earth is always in motion around the Sun, which in turn goes around the galaxy, which in turn is moving. If I go forward or backward in time by one minute to my present location, I should be inside Earth or in outer space. I made further comments on the Time Travel talk page before being referred here. Are there any discussions of this locational displacement problem in time travel discussions? I came to Wikipedia hoping to find a sentence or two about this. Geographyinitiative (talk) 21:08, 21 June 2020 (UTC)[reply]

Moving relative to what? You appear to be assuming that [A] the frame of reference where the star field is, on average, fixed is the frame of reference that a time machine will use, and [B] that the time machine only changes the time, never the location or velocity. Because time machines only exist in Science Fiction, we have no way of knowing whether your assumptions are true or false. To further confuse things, time is not a constant when discussing two observers with different locations and velocities relative to each other. --Guy Macon (talk) 21:16, 21 June 2020 (UTC)[reply]

Thanks for your response. Moving relative to other galaxies and stars and planets. I am sitting 'motionless' in my room, but I am not where I was a minute ago. If I went back in time to 500 BC right now, I would be outside the solar system if I didn't move faster than light to the position of the earth at that time, right? The point is, the time travel sci fi doesn't seem to delve into the locational shifting that would be required to visit ancient or future Earth: ancient and future Earth are not 'here'. Tell me if I am still getting it wrong, but I think this would be mentioned in philosiphocal or scientific discussions about time travel, no? So that's what I want to see some info about on Wikipedia. Geographyinitiative (talk) 23:10, 21 June 2020 (UTC)[reply]

I know I've seen this as a plot point in some time travel stories, but most stories just assume that your motion through time includes corrections for such spatial movement. The T.A.R.D.I.S. from Dr. Who includes such spatial adjustments in its very name. --Khajidha (talk) 23:22, 21 June 2020 (UTC)[reply]

Yes, if this is a question about science fiction, then it's a matter of what the author decides for story purposes. But if that's what you want then it's off-topic for the science desk. --76.71.5.208 (talk) 23:29, 21 June 2020 (UTC)[reply]

Re: "If I went back in time to 500 BC right now, I would be outside the solar system if I didn't move faster than light to the position of the earth at that time, right?", wrong. Again you are ignoring relativity and assuming one particular frame of reference. Maybe the time machine uses the earth as a frame of reference. You don't know.

Re: "The point is, the time travel sci fi doesn't seem to delve into the locational shifting that would be required to visit ancient or future Earth: ancient and future Earth are not 'here'." Wrong again, for the same reason. You say "would be required" as if you knew what would be required. You don't.

Re: "Tell me if I am still getting it wrong", you are getting it wrong. You think you know aspects and limitations of an invention that does not exist and may never exist. You don't.

An author can use any assumptions he wishes. For example. Larry Niven assumes that his transfer booths change location but not time or velocity and further assumes an advanced technology that can compensate for small velocity changes but not large ones. Nothing in the laws of physics supports any of that, but it was convenient for the plot to assume that you can use the transfer booth to go from your job in San Fransisco to your home in the rocky mountains, but would still need a ship to go to mars or the asteroid belt. --Guy Macon (talk) 00:01, 22 June 2020 (UTC)[reply]

Since all backwards time travel stories are fictional, the universe in which they operate is also fictional. For example, that universe could be geocentric. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:48, 22 June 2020 (UTC)[reply]

"People need to be aware that there is a range of models that could explain the observations… For instance, I can construct you a spherically symmetrical universe with Earth at its center, and you cannot disprove it based on observations… You can only exclude it on philosophical grounds… What I want to bring into the open is the fact that we are using philosophical criteria in choosing our models. A lot of cosmology tries to hide that." - George F. R. Ellis, Scientific American, October 1995, Vol. 273, No.4, p. 55

"I have had your newspaper on my desk for weeks, hoping to find time to write you. You say in your headline (Fall), 'Six Physicists Say it is Pos­sible' that the earth stands still. I don’t know who your physicists are, but the situation is much simpler than they seem to think. It is not just possible, it is a fact.

It is also a fact that earth does not stand still. The fact that makes facts of those two apparently conflicting statements is that, as Einstein said, there are no milestones in the Universe, and thus no absolute stan­dard of rest or motion that makes such categorical statements mutually exclusive."

--David Park

Professor of Physics, Thompsonville Physical Laboratory

Williams College, Williamstown, Massachusetts

Source:[2]--Guy Macon (talk) 06:33, 22 June 2020 (UTC)[reply]

Wow! I don't know if my original thoughts hold up, but my original question is not as important as what I have just seen in these quotations. I am sure that the quotations in the comment above this post need to be put somewhere in Wikipedia for the layman readers like me to see. What would you all say is the Wikipedia article that a reader would turn to to understand that physicists can and do take a point of view in which the Earth is both without motion and in motion at once? I know you can say "it's an innate fact so it goes on every page and on no page simultaneously", but I would like to really put these quotes in an appropriate spot on Wikipedia or at least create a sentence that uses them as a source. It seems like a significant and interesting viewpoint that readers ought to be made directly aware of. Geographyinitiative (talk) 07:18, 22 June 2020 (UTC)[reply]

"Look at that beautiful sunset!"

"Actually, the horizon is moving up."

--Guy Macon (talk) 08:53, 22 June 2020 (UTC)[reply]

Perhaps you are seeking Preferred frame#Inertial frames preferred above noninertial frames and Absolute space and time. But you may be reading too much into this. Ellis's "philosophical grounds" are not esoteric ones, but ones of parsimony. Choose a non-inertial reference frame and your laws of motion become more complicated with the addition of fictitious forces. -- ToE 09:55, 22 June 2020 (UTC)[reply]

We also have Geocentric model.  --Lambiam 10:08, 22 June 2020 (UTC)[reply]

Time and space are one and the same concept. By travelling in time you would also be travelling in space. You would move relative to your reference point...you would remain in your room, but be there 5 minutes before. — Preceding unsigned comment added by Anton.Brad (talk • contribs) 09:16, 22 June 2020 (UTC)[reply]

Johnny Alpha killed Hitler by using time bombs to shunt him a few minutes into the future, to when the Earth had moved, leaving him stranded in space. Iapetus (talk) 09:47, 22 June 2020 (UTC)[reply]

The thing is, "time travel" in fiction is generally a magical plot device. The creator is crafting a story, not taking you through a solution of the Einstein field equations. To look at some practical aspects, you and I and the whole Earth and everything orbiting it are in orbit around the Sun; from a Sun-centered frame of reference, we're in constant freefall around it. Changing our trajectory requires doing work, which takes energy. Any more-towards-the-hard-side science fiction will often at least take a stab at grounding things in realistic-sounding physics. "Time travel", described in terms of special relativity, means changing your spacetime four-vector relative to another observer. This involves, again, doing work. Relatively (*rimshot*) small changes don't take much; indeed, you and I do them all the time whenever we move around anywhere. But of course these changes are so incredibly tiny that we never notice. Bigger changes require more energy, lots more. "Time travel" of decades or more relative to a fixed Earth-bound observer requires so much energy that, well, here's the problem. If you can, at-will, "time travel" this much, you have access to so much energy that you are basically a god. You could turn Earth into vapor with a button press, using a relativistic kill vehicle. You could, if able to control and apply the energy more precisely, disassemble the Solar System except something (or someone) you choose, and reassemble it in a slightly different position. The obvious question then presents: if a character has such astounding power, why do they only use it to change their and/or others' worldlines? Of course the obvious "Doylist" answer is that it would totally wreck the plot. ("Why doesn't the Joker just shoot Batman?") And that's why it's called a "plot device"; its purpose in the story is to develop the plot. Real "time travel" forwards is perfectly possible and breaks no physical laws: just accelerate a lot, up to relativistic speeds. When you swing back around to Earth, you'll find that less time has elapsed on your clock compared to those who stayed on Earth, due to time dilation.

Fun related fact: which takes more energy? Shooting something from Earth into the Sun, or out of the Solar System? It's the first one. To get something to hit the Sun, as opposed to just kicking it into a different orbit around the Sun, requires cancelling out all the existing orbital motion that it has around the Sun. You have to bring it to a full stop, in a Sun-centered reference frame, so it falls into the Sun instead of continuing to fall around it. And remember that there's no friction in space; you can't just "hit the brakes". By contrast, kicking it out of the Solar System just requires adding an additional kick to speed it up more until it reaches the Sun's escape velocity, so that the Sun's gravity fails to pull it back. --47.146.63.87 (talk) 16:47, 22 June 2020 (UTC)[reply]

Could not a swing-by be used to use less energy in a trip destination Sun?  --Lambiam 21:30, 22 June 2020 (UTC)[reply]

It doesn't change the total amount of energy "used up". There's no free lunch. What a gravity assist does is "recruit" a planet or other celestial body to do some of the work, which in turn means you don't have to carry the energy yourself as fuel. To decelerate, the craft flies "in front" of the planet's orbital path, which pulls the planet towards it, accelerating the planet's orbit and decelerating the craft's. And indeed, the Parker Solar Probe has been doing exactly this, making repeated flybys of Venus to decelerate so the probe can get into an orbit close to the Sun. Same principle, the probe just wants to get into a tight solar orbit rather than actually hit it. --47.146.63.87 (talk) 22:08, 22 June 2020 (UTC)[reply]

If you reason that way, then I say that by the Law of conservation of energy neither shot requires any energy.  --Lambiam 06:40, 23 June 2020 (UTC)[reply]

True. For a particular course change either you put a lot of energy into changing the velocity of whatever comes out of the exhaust nozzle a lot, or you put the same amount of energy into changing the velocity of the planet you slingshot about a little. Either way everything balances out and both total energy and total momentum are conserved. You do save fuel and reaction mass though. --Guy Macon (talk) 07:11, 23 June 2020 (UTC)[reply]

June 22

Please review the attached pictures, I have noted these in several places in the British Isles over many years and would like to know a number of things, firstly, what causes the grass to grow better in this circular pattern? Is this a known phenomena? Are these related to Fairy circle (arid grass formation) as seen in Namibia?

See fairy ring. PaleCloudedWhite (talk) 09:29, 22 June 2020 (UTC)[reply]

Did you actually take these pictures while lying on your side? :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:42, 22 June 2020 (UTC)[reply]

Took the liberty of stuffing the images in a template so they don't blow out the page length. Revert if there's any issue. They're landing sites for really tiny aliens, obviously! --47.146.63.87 (talk) 17:59, 22 June 2020 (UTC)[reply]

Patterns in grass or crop growth, particularly when it is dry, are often evidence of some previous construction, foundation, or groundwork. This looks like a newbuild residential estate - many of which in the UK are built on formerly industrial sites. Housebuilders are quite content to put down a scandalously thin layer of soil and call it a garden (they happily sold my house with a piece of rebar sticking up out of the grass). So this may simply be the foundation of some old structure (perhaps a chimney, kiln, or furnace) or groundwork (a well or pit). It's a good idea to pull out an old OS map (you can find the 1913 OS map at the National Library of Scotland - but it's not just Scotland) and see what was there beforehand. -- Finlay McWalter··–·Talk 22:56, 22 June 2020 (UTC)[reply]

"What Causes Big Dark Green Circles in Your Lawn?

The appearance of big, dark green circles in your lawn indicates your turf is under attack by the fungal disease known as fairy rings. This annoying fungus can appear on all species of turf... The appearance of the fairy ring depends on the species of fungus infesting the lawn. The rings are semi-circular or circular and vary in size."[3]

--Guy Macon (talk) 05:50, 23 June 2020 (UTC)[reply]

I too think the Fairy ring theory (already pointed out in the first reply) is far more plausible; just look how similar this appears to some of the images in the article, one of which I have copied here.  --Lambiam 06:33, 23 June 2020 (UTC)[reply]

Thanks All, I agree that these are most likely fairy circles as caused by fungus. This is not my garden, just by the way, its a local park. Can anyone tell me if there is any correlation to the Namibian fairy circles please? Thank you.

Probably not. The ones in Nambia are dry earth with no grass, and do not seem to be associated with fungus. Also, the Nambian circles have a negative correlation to rain, and the British Isles are not exactly deserts. --Guy Macon (talk) 12:24, 23 June 2020 (UTC)[reply]

I've just zoomed-in on the OP's images and they seem to have a circle of bare earth on the outside of the circle of green. I don't recall seeing that before in relation to a fungal fairy ring and wonder whether it might have been the imprint of a circular object of some kind? Perhaps like this? Alansplodge (talk) 15:45, 23 June 2020 (UTC)[reply]

Hmmm. Could be. One test would be to look carefully and see how circular the circle is. A man-made object would tend towards being a perfect circle, while anything biological would tend towards being at least somewhat irregular. --Guy Macon (talk) 19:42, 23 June 2020 (UTC)[reply]

It is definitely "somewhat irregular" (eventually, the fairies get dizzy dancing around in a circle). 107.15.157.44 (talk) 20:53, 23 June 2020 (UTC)[reply]

The suggestion that it is from something like this is not likely as this is a public park between houses...The Snail Park in Milton Keynes and is unlikely to have had a swimming pool erected in it. https://www.google.com/maps/place/Snail+Park,+Rockspray+Grove,+Walnut+Tree,+Milton+Keynes+MK7+7EP/@52.0191366,-0.6960534,17.65z/data=!4m5!3m4!1s0x4877ab4ac925800f:0x5d0fa8dacef9c62d!8m2!3d52.0199051!4d-0.6959125 — Preceding unsigned comment added by Anton.Brad (talk • contribs) 08:47, 24 June 2020 (UTC)[reply]

It is quite normal for a circle resulting from fungal growth to have a 'dead zone' - our article on fairy rings states, "One of the manifestations of fairy ring growth is a necrotic zone—an area in which grass or other plant life has withered or died". Though it may be more usual for the necrotic area to be on the inside of the ring - in Pests, Diseases and Disorders of Garden Plants by Stefan Buczacki and Keith Harris, it states that grass growth is diminished due to the fungal mycelium on the inside of the ring exhausting available nutrients, dying, and forming "an impervious layer which deprives the grass roots of moisture". PaleCloudedWhite (talk) 08:58, 24 June 2020 (UTC)[reply]

Splendid answer PaleCloudedWhite; the paddling pool hypothesis dies here. Alansplodge (talk) 17:40, 24 June 2020 (UTC)[reply]

June 23

In the article List of stars in Cassiopeia the stars are shown as having a distance in light years. When I click through to (some of) the individual star articles, the distances are significantly different. Is this an error or is there a factor I am unaware of to take into account? EG Gamma Cassiopeiae says distance 550 ± 10 ly yet the 'List of...' says 613 ly. -- SGBailey (talk) 10:30, 23 June 2020 (UTC)[reply]

Wow, how the months fly by ... it seems like only last week, but it was actually six months ago when I quipped:

Yeah - so if you're looking for an almanac or all-sky survey, Wikipedia is categorically the wrong place to pull your numerical data from. Just this week I was watching science-talks out of Keck, so my mind is a little bit pre-conditioned... but if I needed an all-sky catalog, I would go straight to Pan-STARRS, or MAST, or the USNO - (comically, the entirety of the USNO digital products have been "offline" for most of FY2020 due to some grumbling about our government budget or technical reasons or manpower shortages - ... have we mentioned that we're in a literal national emergency these days, and that the effects have been very specific and profound? I had to go to an unofficial almanac to find the true solstice last week... and it pained me...)

...Those horrible data catalogs are the ones you want to use, if you actually need the values for any actual purpose other than general interest. Eschew using data that you copy off of Wikipedia: while our encyclopedia is great for general interest, our anonymous-editable format and our volunteer curator-editor culture are simply unsuitable for data retrieval questions.

Anyway, if these sources are too technical, you might find a software package like Starry Night or the free software KStars much easier to use: you can just click on the star or deep-sky-object, and the graphical interface will pop right up with a full catalogue of data on it. Those are essentially front-ends to PPMXL, a catalog of scientific merit, but of course the first line of the paper that introduces PPMXL will refer you straight back to the US Naval Observatory catalog....

Nimur (talk) 15:06, 23 June 2020 (UTC)[reply]

Until not that long ago star distances from us were notoriously fuzzy compared to say paper road maps. Latitude or longitude was good to what would be several feet on Earth at worst but distances were horrible, though error wasn't too bad for the highest parallaxes like alpha Centauri. The cosmic distance ladder has since improved and Gaia spacecraft data starting from the mid 2010s is asymptotically approaching 10 percent at large fractions of the galaxy width and much better for close stars. Sagittarian Milky Way (talk) 15:52, 23 June 2020 (UTC)[reply]

I would beg to differ, or at least to qualify that, with a "citation-needed" - the field of stellar spectroscopy has a long history; measurement of the spectrum is - and has historically been - the provincial home for the most precise and accurate numerals ever measured, among all other scientific pursuits. (Hey, did I just mention that I've been watching videos from Keck this week? Here is Spectroscopy: How Astronomy Really Gets Done, a video lecture by John O'Meara, the Chief Scientist of the Keck observatory).

Yeah - so the conversion from redshift, or "z-index", to units of conventional distance is a little more complicated - but it is both accurate and precise - extraordinarily so, in the scientific sense of those words - though it is parameterized - by Hubble's law. The precise numerical value of the parameter - particularly, the Constant - has a notorious history - but it's not "fuzzy." The word that I would use, actually, would be "sharp," because we use sharply defined discrete spectral lines like the examples shown in our article. "Fuzzy" is the antithesis of real astronomy - we can regale you with everything you need to know about what causes "fuzziness," and how we have built up the entire modern discipline of optical astronomy to, um, resolve that.

If I may put a more sharp point on my commentary - why are you trying to measure distance-to-stars in the wrong units? Real astronomers don't use meters, and they don't even use "light-years," because those are useless units. Were you planning to walk, proverbially or literally, from "here" to "there"? ... Well, you can't. So, why would you measure distance to a star in the same way that you measure distance to the corner store? It's a dumb way to measure, and it's no wonder that when you get right down to the details, you find them confounding. There are confounding factors about expansion; about apparent motion; about reference frames; about relativity. There are confounding factors about time-scales and distance-scales and weirdnesses of gravity that only matter to objects-the-size-of-universes. If you can't evolve your brain to think different about distance, you won't ever really be able to grok distance as it applies to astronomy - and there will never exist any data-table of stellar distances that shall be complete- or consistent- enough to be useful to you.

Nimur (talk) 16:13, 23 June 2020 (UTC)[reply]

Stars are not subject to cosmological redshift (galaxies are), so you can't measure their distances using spectroscopy. The most precise way to measure stellar distances is through parallaxes, and, exactly as SMW said, this has only recently become possible for a large number of stars, with Gaia being the current gold standard. In the German article, the value of 550 Lyr quoted in the question is sourced to the Hipparcos satellite; I don't know where the other value comes from. --Wrongfilter (talk) 16:30, 23 June 2020 (UTC)[reply]

Well, that's not correct either - the first measurements of optical doppler-shift were on stars. I think you are conflating all red-shift with red-shift that is unique to the expansion governed by Hubble's law, ... but that is a categorical error. Any relative motion - any at all - can provide a measurable doppler shift.

Nimur (talk) 16:37, 23 June 2020 (UTC)[reply]

That is an error that I would never make, in fact I can get quite angry when cosmological redshift is associated with relative motion at all. Stellar redshifts are caused by the Doppler effect, which means you can infer their line-of-sight velocity from them, but not their distances. And, if you remember, the question was about distances. --Wrongfilter (talk) 17:44, 23 June 2020 (UTC)[reply]

As an aside - for anyone who wants to follow up on my strong claims about accuracy and precision, here's some further reading material:

• Daniel Rothbart and Suzanne W. Slayden, "The Epistemology of a Spectrometer," Philosophy of Science 61, no. 1 (Mar., 1994): 25-38. Available online.
• Measurement in Science, from the Plato Encyclopedia of Philosophy.

Both of these provide a fine overview on the role of precise and accurate measurement - and the unique role of astronomical spectrometry in the development of the modern theory of scientific knowledge. In particular, optical astronomical spectroscopy plays a very real role in the history of science and the discovery of the fundamental physical constants, which are the absolute minimum set of data-entries that are necessary to quantify everything that we, as a species, know. These numbers are the most accurate and precise measured quantities that we have - they must be - because every other measurement we can possibly make is deeply and inherently tied to these measured properties of the universe.

Nimur (talk) 16:37, 23 June 2020 (UTC)[reply]

Sure for a long time we could measure star redshift and peculiar velocity and parallax to tiny, tiny amounts of nanometers and tiny fractions of c and small pieces of arcseconds, great but the star distances I remember from old books as a kid were not that great beyond several hundred light years and that's a lot of the naked eye prominent stars. I remember distance estimate differences of 50 or 100 percent for Deneb and still significant by Earth standards for Antares, Betelgeuse, Alcyone, Polaris, large differences for the nearest and furthest galaxies though those are pretty good now with the Hubble constant being pinned down and all. Star distances from the right sources are pretty good now too, something halfway across the galaxy will be a first order approximation or so but who cares, they're dim and numerous. Sagittarian Milky Way (talk) 17:16, 23 June 2020 (UTC)[reply]

As I recall there weren't enough rare stars with good absolute magnitudes with some effect on knowledge of stellar evolution and the Gaia has helped greatly with this. Sagittarian Milky Way (talk) 17:18, 23 June 2020 (UTC)[reply]

So to summarise: "It isn't surprising that they are different in Wikipedia, and unless I want to spend significant effort tracking down reliable sources, I should just put up with it." -- SGBailey (talk) 20:47, 23 June 2020 (UTC)[reply]

Isn't that generically true for all info on Wikipedia: "It isn't surprising that some information on Wikipedia is inaccurate, and unless someone volunteers their effort tracking down reliable sources, you have a choice: either put up with it, or be that volunteer."  --Lambiam 10:11, 24 June 2020 (UTC)[reply]

Will smartphone cameras ever be able to produce DSLR Quality photos with the technologies available and being developed? And what are the main limitations of smartphone cameras over DSLR? Clover345 (talk) 21:21, 23 June 2020 (UTC)[reply]

Sensor and lenses in a smartphone are so much smaller and simpler, for example a full-frame 35mm sensor measures 864mm2 while a 1/1.7” smartphone sensor only measures 43mm2 ([[4]]). And the lenses in a smartphone mostly are one, two or three (maximum today five), while a professional objective for reflex cameras can consist of fifteen or more elements (the 'single' in DSLR doesn't mean that the objective consists of one single lens, but that there is only a single lens system serving both the sensor and the viewfinder.) As all progress in quality seem to benefit both types of cameras, smartphone cameras will probably always remain the 'cheaper' one. 2003:F5:6F05:BC00:744A:96C9:C7E9:8B5 (talk) 22:07, 23 June 2020 (UTC) Marco PB[reply]

Is this why photos taken on smartphone cameras don’t have the same detail and depth as that taken on a DSLRs especially when photos are enlarged? Clover345 (talk) 22:23, 23 June 2020 (UTC)[reply]

Yes. A smaller sensor means either less or smaller pixels and less pixels means less resolution, smaller pixels means more sensitivity to noise. Less and smaller lenses means less luminosity and contrast. The link above explains all this and better. By the way there are so called Smartphone add-ons like this [[5]] Pictar Pro for $150 or several wide, makro, micro and tele lenses [[6]] or this Black Eye for $30 [[7]]. I find the idea ridicolous, because working with the same sensor you cannot get much better pictures than with the smartphone alone. And if somehow good photos matter to you, with the money you get a low end digital camera ways better than any smartphone, as Macon also says. 2003:F5:6F05:BC00:F1BF:F34C:1D5C:6819 (talk) 19:23, 24 June 2020 (UTC) Marco PB[reply]

Can they put a cylinder or cone frustum ridge on the back and fold the path to it with a 45 degree mirror? Someone must've patented the idea by now if it's not too simple. Sagittarian Milky Way (talk) 16:16, 24 June 2020 (UTC)[reply]

That only changes the shape of the space needed, not the amount of space needed. Unless someone comes up with some different physics than lenses and sensors, it will always be true that high quality photography requires a lens system with a large (compared to the space available in a smartphone) diameter and length.

The best practical advice is to get a low-end digital camera with a larger lens system and good reviews. For example the Canon PowerShot ELPH 190] costs $150 and takes far better pictures than any smartphone. --Guy Macon (talk) 16:28, 24 June 2020 (UTC)[reply]

I didn’t realise even point and shoots were better than smartphones. So what’s the main advantages of DSLRs or mirrorless cameras over point and shoots. Clover345 (talk) 20:51, 24 June 2020 (UTC)[reply]

Less diffraction and more light gathering capability with all its benefits, larger sensor, interchangeable lenses, more pixels, more features, better build quality, probably more that I don't know or remember now. Sagittarian Milky Way (talk) 01:39, 25 June 2020 (UTC)[reply]

I know about diffraction and shitty f/ratios, someone (not me) might be willing to have a clunky phone back to have a camera that's better than one only a few millimeters thick even though it isn't as wide, thick, bright or sharp as "real lens". Sagittarian Milky Way (talk) 18:48, 24 June 2020 (UTC)[reply]

If the image sensors of a camera can be manufactured to a much higher resolution (without losing much sensitivity), a compound eye as found in insects could serve as a model for a compound lens system whose separate images are fused (using quite some computing power) into a single image, thus creating a virtual lens with a much larger aperture. Compare the idea of very-long-baseline interferometry, in which fusion also achieves much higher resolution than any individual telescope is capable of.  --Lambiam 21:53, 24 June 2020 (UTC)[reply]

Is there any info regarding the structure of antibodies developed by recovered individuals exposed to the present virus?--109.166.135.226 (talk) 23:59, 23 June 2020 (UTC)[reply]

There is a race going on to find powerful antibodies that can be the basis of a COVID-19 vaccine or even a drug.^[8][9][10] The urgency should be obvious for humanitarian reasons, but another powerful incentive is that the company that is the first to market will stand a good chance to make an ungodly profit, while latecomers may have wasted tremendous amounts of money – unless the earlier vaccine or drug is not very effective and theirs is much better. The profit motive is at the same time a strong reason not to share much information about what each company's scientists have been able to find out about the structure of antibodies that have been identified. So the published research, like this article, mainly comes from academia.  --Lambiam 13:23, 24 June 2020 (UTC)[reply]

See also Antibody#Structure.--Shantavira|^{feed me} 16:53, 24 June 2020 (UTC)[reply]

I see there it says about the variable V region and the constant C region of the glycoprotein/antibody.--109.166.135.226 (talk) 13:25, 25 June 2020 (UTC)[reply]

It seems that some alternative variants to vaccins have been tried so far, like plasmapheresis. The use of alternatives generates some related questions re the identification of substructures of antibodies.--109.166.135.226 (talk) 13:41, 25 June 2020 (UTC)[reply]

June 24

OK brainiacs, what's this plant? xD ty Zindor (talk) 22:25, 24 June 2020 (UTC)[reply]

Some kind of liverwort? DuncanHill (talk) 22:29, 24 June 2020 (UTC)[reply]

Looks like you've narrowed it down Duncan, thanks. It would be great to find the species out. The habitat itself is near the shore of a massive reservoir, so some humidity, but the area is otherwise baking hot for lots of the year so i'm thinking it might be a desert species. I believe the specimen had fallen off a rockface. Zindor (talk) 22:41, 24 June 2020 (UTC)[reply]

Asterella californica?  --Lambiam 09:46, 25 June 2020 (UTC)[reply]

@Lambiam: Yeah it could well be, i'm currently trying to differentiate whether it's A.californica, A.bolanderi or Mannia californica. It's a shame i didn't take more photos as i was too distracted photographing the superbloom. Zindor (talk) 12:11, 25 June 2020 (UTC)[reply]

June 25

How does plasmapheresis from recovered individuals from the present virus operate? Does it require plasma fractionation and/or the identification of specific antibodies from this virus? Thanks!--109.166.135.226 (talk) 15:42, 25 June 2020 (UTC)[reply]

Antibodies bind to specific white blood cell surfaces, along with other surfaces which the immune system wants the white blood cells to try to eat. They can be extracted from solution using that method, but their molecular weight often falls into a certain range of Daltons, so often blood laboratory centrifuge separation can work too. Identifying antibodies in plasma is a multi-stage process including microscopy, spectograpy, and sometimes fluorescence labeling. 98.33.89.17 (talk) 17:43, 25 June 2020 (UTC)[reply]

What data/research is there re the use of disinfectants against the present virus? Which disinfectant is more effective? How are the effectiveness of disinfectants and the required level of concentration to be effective determined?--109.166.135.226 (talk) 15:53, 25 June 2020 (UTC)[reply]

As viruses/bacteria go, the coronavirus family is quite fragile outside of the body, and pretty much any disinfectant kills it on surfaces. Compare this with MRSA, which is really hard to kill.

Surfaces are not the main way people get Covid-19. Disinfecting surfaces helps a little, and washing hands helps a little more, so they are both worth doing, but the main way it spreads is through the air. The way to reduce that is masks, social distancing, and quarantining yourself if you are sick. --Guy Macon (talk) 16:31, 25 June 2020 (UTC)[reply]

Just to clarify, it is also not free viruses through the air, it's through airborne water droplets, which is why properly made, but otherwise cheap, cloth masks are actually surprisingly effective in stopping its transmission. Normal breathing puts out a lot of rather large (especially on the molecular scale) droplets (though too small to be visually identifiable) and cloth masks generally have a pore size that stops these fairly easily. This guide describes the current understanding pretty well. The reason why they are much more effective for preventing outbound transmission than incoming transmission is if an infected person breathes out through a mask, the mask minimizes the amount of droplets they put into the air around them. If a healthy person wears the mask, but is around a sick person who isn't, the droplets are still in the air and may collect on all sorts of surfaces around the healthy person, including their hands, face, eyes, exterior of their own mask, etc., all of which carry individually small, but taken in the cumulative rather large, risks for transmission. Proper cleaning and disinfection is part of a good comprehensive mitigation strategy, but the most important part is for contagious people (many of whom may be contagious for several days before presenting symptoms) to wear masks. --Jayron32 18:51, 25 June 2020 (UTC)[reply]

"No conclusive studies have been conducted on differentiating between the modes of transmission of viruses via droplets and aerosols; hence, unresolved dichotomy". Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy (13 June 2020). Alansplodge (talk) 19:30, 25 June 2020 (UTC)[reply]

From the same paper:

"The transmission of droplets and aerosols has significant implications on healthcare workers and caretakers managing patients infected with COVID-19, and providing appropriate PPE is, therefore, of utmost importance. The facemasks play a major role in preventing both droplets and aerosols from transmitting the disease from an infected person to a host."

"Many respiratory viruses are believed to transmit over multiple routes, of which droplet and aerosol transmission paths become paramount, but their significance in transmitting the disease remains unclear. In general, infected people spread viral particles whenever they talk, breathe, cough, or sneeze. Such viral particles are known to be encapsulated in globs of mucus, saliva, and water, and the fate/behavior of globs in the environment depends on the size of the globs. Bigger globs fall faster than they evaporate so that they splash down nearby in the form of droplets. Smaller globs evaporate faster in the form of aerosols, and linger in the air, and drift farther away than the droplets do."

--Guy Macon (talk) 21:56, 25 June 2020 (UTC)[reply]

The cold virus (coronavirus) lasts 3 to 12 hours on hard nonporous surfaces. It is an enveloped virus, and is deactivated by alcohols, phenols, aldehydes, chlorine (sodium hypochlorite), and soap. --83.137.6.229 (talk) 08:07, 26 June 2020 (UTC)[reply]

How can you split Zinc Sulfide into its original elements using basic means? UB Blacephalon (talk) 16:55, 25 June 2020 (UTC)[reply]

Superheated steam. 98.33.89.17 (talk) 17:39, 25 June 2020 (UTC)[reply]

So how would you do that? All this tells me me is that really hot steam is involved. UB Blacephalon (talk) 19:44, 25 June 2020 (UTC)[reply]

Step 1: put ZnS in an airtight pressure reactor vessel.

Step 2: add really hot steam until it dissolves.

Step 3: Profit? EllenCT (talk) 20:49, 25 June 2020 (UTC)[reply]

Well is there a way to build that because I need to do it DIY style and I don't have one of those lying aroung anywhere. And no its not a profit I'm looking for Its that i want to have a sample of every pure element on the periodic table that I can get my hands on. UB Blacephalon (talk) 21:59, 25 June 2020 (UTC)[reply]

How about electrolysis? According to the article, Martin van Marum reduced zinc and antimony salts electrolytically in 1785. --83.137.6.229 (talk) 08:34, 26 June 2020 (UTC)[reply]

For these two elements, it will be much easier to just buy them, rather than a DIY compound extraction. Both are easy to buy. Graeme Bartlett (talk) 00:45, 27 June 2020 (UTC)[reply]

Hmmm.....Ya you might be right but I do have ZnS just lying around. So there's really no way to extract both of them from it by myself? UB Blacephalon (talk) 03:30, 27 June 2020 (UTC)[reply]

Yes, but as reported here Zinc_sulfide Zink and Sulfur react violently releasing much heath, and the product is not soluble in water. All this suggests that both elements are strongly bound in Zinc sulfide. And that means that it takes much energy and effort to separate them again, so there is possibly no way of doing it just by using basic means. 2003:F5:6F09:6700:DCD9:66B6:437B:58AF (talk) 09:29, 27 June 2020 (UTC) Marco PB[reply]

Huh? What compounds can I separate using basic means that results in original elements? UB Blacephalon (talk) 13:16, 27 June 2020 (UTC)[reply]

Oxygen and Hydrogen can be easily obtained from water for example, with a battery and two wires, also many metals can be obtained from their salts by electrolysis (search "Electroplating"). But some elements like Fluorine and Sulfur are very reactive and are not easily obtained pure with electrolysis because they react with most electrodes and with the other element, so you have to use Gold or Platinum electrodes and to take measures in order to keep the reaction products separated, and this I don't call basic means. In your case you can probably separate on the kitchen table some Zinc as pure element from the sulfide, but it could be ways more difficult to obtain pure Sulfur. 2003:F5:6F09:6700:DCD9:66B6:437B:58AF (talk) 18:00, 27 June 2020 (UTC) Marco PB[reply]

Ooh yes. I also have a few more substances lying around like CaCl and litmus powder, but I'm not sure what to do with them, do you? UB Blacephalon (talk) 21:15, 27 June 2020 (UTC)[reply]

What is the easiest way to convert carbonic acid in seawater to a solid on a gigaton scale? Can the material be used for seawall construction? 98.33.89.17 (talk) 17:24, 25 June 2020 (UTC)[reply]

The easiest way is to reduce atmospheric CO2 concentration, which will cause Q>K on the equilibrium between CO2 and carbonic acid, thus driving the reaction away from carbonic acid formation. Making a building material out of the acidified ocean itself is not easy at all, as nature itself shows. Less acidified sea water will have less bicarbonate than now and more carbonate than now, and it is carbonate that marine organisms use to make calcium carbonate for sea shells and coral. They cannot use bicarbonate nearly as easily. Neither can we. --OuroborosCobra (talk) 18:03, 25 June 2020 (UTC)[reply]

Surely there must be an answer to the specific question about the most efficient path from carbonate to solids? EllenCT (talk) 21:01, 25 June 2020 (UTC)[reply]

Add calcium hydroxide to the water; turning the carbon dioxide into calcium carbonate before it becomes carbonic acid. The only problem is that calcium carbonate as a wall material is susceptible to erosion (see Cliffs of Dover). Zindor (talk) 21:49, 25 June 2020 (UTC)[reply]

A bigger problem could be that the only practical way of producing megatons of calcium (hydr)oxide in the first place is to heat megatons of calcium carbonate to 900 °C (most conveniently by burning a lot of coal) to free exactly as much CO2 into the air as your Ca(OH)2 will ever bind from seawater. The natural source of CaO are the vulcans, and they produce it the same way: by heating calcium carbonate and releasing the CO2 into the atmosphere. 2003:F5:6F09:6700:DCD9:66B6:437B:58AF (talk) 08:40, 27 June 2020 (UTC) Marco PB[reply]

• I believe that our article on Ocean storage of carbon dioxide will provide superior answers than the discussion above. --Guy Macon (talk) 22:01, 25 June 2020 (UTC)[reply]

No, that's a liquid, not a solid. 98.33.89.17 (talk) 04:17, 26 June 2020 (UTC)[reply]

The question is not very practical. A seawall can be constructed cheaper and more effectively by other means than turning seawater into limestone. As User:Zindor wrote, you can neutralize an acid with alkali, this turning it into a salt, like with table salt. --83.137.6.229 (talk) 09:04, 26 June 2020 (UTC)[reply]

What other means are less expensive than not having to transport the construction materials to the building sites, assuming there is an abiotic reaction which can be efficiently performed by compact reactors? 98.33.89.17 (talk) 22:47, 27 June 2020 (UTC)[reply]

That's just it, though. Your assumption is unfounded. There isn't a cheap and effective way to make limestone out of seawater. It's much cheaper to use other means, including trucking in materials produced elsewhere. --OuroborosCobra (talk) 01:16, 28 June 2020 (UTC)[reply]

• This question is a great example of someone who has never read How To Ask Questions The Smart Way The OP created a heading and a first sentence talking about fixing ocean carbonate, and only later did those attempting to answer the question find out that what he really wants to do is build a seawall and apparently has zero interest if carbon sequestration. (He may change his tune if the sea level rises and submerges his seawall...   :(   ) He would get a better answer by simply looking at a bunch of seawalls and seeing what they are made of. --Guy Macon (talk) 01:48, 28 June 2020 (UTC)[reply]

What factors are involved in determining some people to be asymptomatic to the present virus? Are they immunological?-Is it possible by analyzing blood samples from uninfected persons to determine whether they are asymptomatic if infected?-109.166.135.226 (talk) 18:59, 25 June 2020 (UTC)[reply]

If you ask someone who is testing positive on a PCR swab test for active viral shedding whether they have symptoms, and they say no, then they are an asymptomatic infection case. The SARS-Cov2 virus often causes no symptoms in infected individuals, perhaps in a majority of cases. We know what causes the likelihood of symptoms, which are comorbid, often pre-existing conditions. Obesity, high blood pressure, diabetes, and advanced age are the big ones I can remember off the top of my head. EllenCT (talk) 20:58, 25 June 2020 (UTC)[reply]

And COPD and heart disease. This is a list of maintained by the CDC of underlying medical conditions that pose an increased risk for people of any age. For all we know, remaining clinically asymptomatic while testing positive is not an immunological issue. But much around this disease still remains unknown or uncertain.  --Lambiam 23:28, 25 June 2020 (UTC)[reply]

But can an uninfected person know by some test the (virtual?) state asymptomatic or not asymptomatic in the case of a possible infection, but without getting the infection?--109.166.135.226 (talk) 11:30, 26 June 2020 (UTC)[reply]

There was a radio report today which said the antibody numbers could be ten times the number of confirmed cases in many regions. 98.33.89.17 (talk) 04:20, 26 June 2020 (UTC)[reply]

A link to the report (and radio station)?--109.166.135.226 (talk) 11:32, 26 June 2020 (UTC)[reply]

I can't find the exact report I heard, but this is the same story. 98.33.89.17 (talk) 22:48, 27 June 2020 (UTC)[reply]

How do Tunnel Boring Machines scan ahead to areas of ground they’re about to bore to detect services or unexpected ground or other anomalies. 90.194.57.205 (talk) 20:09, 25 June 2020 (UTC)[reply]

They do not. The exploration is done before the tunnel boring starts. Ruslik_Zero 20:28, 25 June 2020 (UTC)[reply]

In any case, TBMs are only used at depths well below those of any services. Deeper geotechnical investigations are carried out using geological records and boreholes.--Shantavira|^{feed me} 08:08, 26 June 2020 (UTC)[reply]

Wishful thinking Shantavira in the case of the London Crossrail tunnelling project:

"Subterranean London is riddled with Tube tunnels, secret passages, Roman ruins, high-voltage cables, long-forgotten aquifers and deep building foundations. The route squirms past these obstacles, passing just 1.5m over the Tube's Northern Line. During the long desk-phase that preceded tunnelling, designers scrutinised yellowed plans for London buildings. For some, they had diagrams of what was actually built. For others, they just had the initial plans. Crossrail's surveyors estimated the size of foundations by examining buildings. Then there was the problem of bombs. 6Alpha [a risk management consultancy] studied records kept by wartime ARP wardens, local authorities, and at times even the Luftwaffe, to identify areas along the route which presented the biggest unexploded ordnance threat. Separate contractors were then sent to survey these areas. So far, no unexploded bombs have been found". Crossrail and Unexploded WWII Bombs Alansplodge (talk) 16:42, 26 June 2020 (UTC)[reply]

Due diligence sometimes falls short, as with the Lake Peigneur disaster. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:47, 26 June 2020 (UTC)[reply]

"Transistor#Transistor_as_a_switch" and "Bipolar_junction_transistor#Regions_of_operation" state that the saturation mode is analogous to a switch in the "on" position, and, if I understand what they're saying correctly, allowing current flow between the collector and emitter. Using an online circuit simulator on a website that seems to be on Wikipedia's blacklist, saturation is achieved if both the collector and emitter voltages are the same (-5), and the base voltage is higher/more positive (+5); doesn't this mean that there is no current flow between collector and emitter? ZFT (talk) 22:49, 25 June 2020 (UTC)[reply]

The muscle fatigue article distinguishes between neural and metabolic fatigue, but doesn't explain how a person recovers from each one, and it's not exactly clear whether neural fatigue limits only muscular force, or also stamina. I.e. is the idea that a novice strength trainer has big enough muscles to lift 200 pounds, but is limited at first by neural fatigue to lifting only 100? Let's say they start out able to lift 100 pounds for 3 repetitions. After a few days, they can lift 100 pounds for 5 repetitions. What has happened--is that an increase in nerve capacity rather than muscle capacity? If they do the 5 reps one day, the next day they might only be able to do 4: whatever has fatigued seems to take a few days to recover. Is that explained somewhere? Are these nerves the ones directly in the exercised muscles, or are they in the central nervous system, so increased arm lifting capacity also increases the ability to leg lift?

Motivation: I'm doing some push-ups as indoor exercise during the pandemic. I'm not obese but I'm out of shape so my rep counts are still pretty low. I'm trying to understand what I'm observing and what to expect if I can keep it up. I'm planning to add some other exercises like stair climbing but haven't done this yet.

Thanks -- 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 23:49, 25 June 2020 (UTC)[reply]

Lactic acid #Exercise and lactate might be relevant, but that article requires a degree in biochemistry to comprehend. 107.15.157.44 (talk) 00:30, 26 June 2020 (UTC)[reply]

Do these papers help?

• Neural adaptations to fatigue: implications for muscle strength and training
• Neural Adaptations to Fatigue: Implications for Muscle Strength and Training
• Rethinking CNS Fatigue and Recovery: What’s Really Going On Post-Workout?
• Is Resistance Training to Muscular Failure Necessary?

Note to other experienced Wikipedia editors: When I read the above papers I learned things that I didn't get from our articles. This usually means that [A] our articles need to be improved, or [B] the information is bullshit. Any opinions about which is true in this case? I found a bunch of other non-academic sources, and don't know how to evaluate them. For what it is worth, here are a few:[11][12][13][14][15][16] I have no idea whether what I just read is useful information or a steaming pile of crap. --Guy Macon (talk) 01:21, 26 June 2020 (UTC)[reply]

Guy, it is hard to edit articles related to biology or physiology because the MEDRS police go crazy reverting anything but meta-studies if the source or the article is about any topic that could remotely be related to human health. So yeah our articles in those areas are often deficient. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 02:58, 26 June 2020 (UTC)[reply]

which is a Good Thing, because there are wagonloads of nonce results and crap theories out there, some of which have a circle of devoted followers who'd only be too happy to edit this in.  --Lambiam 09:01, 26 June 2020 (UTC)[reply]

No that is crazy, the idea of science is to examine the available information, even though it can be in a malleable state. So when we write about scientific subjects on wikipedia, we should describe whatever info that is out there that has some level of academic recognition. When the topic is something like black hole astrophysics we don't get too much trouble about that. Medical topics are treated a bit specially because we don't want people doing crazy health interventions on themselves: ok fine, do no harm. The problem is some MEDRS goons tend to interpret anything having to do with biology, such as molecular genetics, as medical, which is ridiculous (it is more like astrophysics). Even if it is medical it is ok to relax some of the time. Christiaan Barnard did the world's first human heart transplant over 50 years ago, and wrote a historically important paper about it in a medical journal at the time. The paper has been cited by more than 1000 other papers in the medical literature since then. Our article about heart transplants can't cite that paper under MEDRS, because it is a primary source. We wouldn't want some reader messing up a do-it-yourself heart transplant in their kitchen because they read a famous 50 year old paper by an actual surgeon, instead of a meta analysis with its own potential COI. As a popular youtube tool reviewer likes to say, jeezeless. We are supposed to be here to bring knowledge to people, not keep it away from them. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 10:06, 26 June 2020 (UTC)[reply]

June 26

Hello I'm working on Saturn V and I found that it is a unsourced paradise. Could you find some sources in general as there is not one place that does not have sources. Thanks, Signed,The4lines |||| ^{(You Asked?) (What I have Done.)} 03:42, 26 June 2020 (UTC)[reply]

There are nearly 100 references, and some of them are used more than once. Bubba73 ^{You talkin' to me?} 05:42, 26 June 2020 (UTC)[reply]

Could morals, or even mores(such as respectability seeking, “healthymindedness”, crudity, monogamy, etc), or their opposites, be transmitted by microbes? What about kindness and cruelty?Rich (talk) 04:00, 26 June 2020 (UTC)[reply]

Almost certainly no. microbes simply don't contain enough information, and most of the information they do contain is instructions for making more microbes. Also there is no known mechanism that would have the effect you describe. Also, in general most microbes cannot cross the blood brain barrier.

That being said, if you are willing to take a small step upwards in complexity, Toxoplasma gondii has an effect on humans similar to what you are talking about. --Guy Macon (talk) 04:32, 26 June 2020 (UTC)[reply]

Fun facts from Toxoplasma gondii#Behavioral differences of infected hosts: Toxoplasma infection was 2.4 fold more common in people who had a history of manic and depression symptoms, and students who tested positive for T. gondii exposure were 1.4 times more likely to major in business, 1.7 times more likely to have an emphasis in "management and entrepreneurship", and 1.8 times more likely to have started their own business. --Guy Macon (talk) 04:38, 26 June 2020 (UTC)[reply]

It's well known that traumatic brain injuries can make people become violent. Thus we see things like millionaire professional football players going off on idiotic crime sprees. It's not too big a stretch to imagine some infections having the same result. And as Guy Macon says, Toxoplasma has a longstanding suspicious relationship with schizophrenia and other mental illnesses. As for positive changes, I haven't heard of any bacterial or viral agents causing that, but there's ongoing research as to whether plant extracts like psilocybin mushrooms (or other chemicals like MDMA) can do that: see MAPS for some info. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 06:22, 26 June 2020 (UTC)[reply]

Looking at this the other way, it's feasible that certain human behaviours and moral codes have evolved over time as a response to the prevalence of infectious microbes i.e. humans change their behaviour in order to minimise transmission, and over time these behaviours become codified into societal morals. Witness the massive change in human societies caused by the current pandemic - it isn't difficult to imagine that where such pressure exists over a prolonged period, human behaviour becomes permanently altered (sexual morals might be an example). PaleCloudedWhite (talk) 06:24, 26 June 2020 (UTC)[reply]

Not the transmission of morals but viruses can influence human behavior. I am familiar with this case. An individual had an episode of severe abdominal flu during an epidemic. Upon recovery it was found that he had autoimmune hemolytic anemia and a genetic test showed that 9% of his DNA was epigeneric material. No visible influence on his behavior but potentially... AboutFace 22 (talk) 17:24, 26 June 2020 (UTC)[reply]

Thanks to all for valuable information and comments...Even if microbes can’t cross the blood brain barrier, they could still manipulate hormones, couldn’t they? Couldn’t they infect the peripheral nervous system also? I’ve heard viruses like herpes do something akin to that. With some time of illness and/or changed hormones, could the blood brain barrier be breached? Also, isn’t the blood brain barrier less effective for young children?Rich (talk) 19:09, 27 June 2020 (UTC)[reply]

Please see Table 1 on page 192 here. As most social behavior is learned nurture instead of ancestry nature, this article may be also of interest. 98.33.89.17 (talk) 22:53, 27 June 2020 (UTC)[reply]

How effective is the sun shield used on recent Starlink satellites? (how many magnitudes of brightness reduction?) Bubba73 ^{You talkin' to me?} 05:41, 26 June 2020 (UTC)[reply]

Current Starlink satellites have an average apparent magnitude of 5.5 when on-station and brighter during orbit raise. We don't have firm numbers for the new design because they need to experiment with different attitudes, especially during boost, and it wouldn't be unusual for the shade design to go through several iterations, each more effective than the last. Right now it looks like they will be able to hit magnitude 7 or better with the current design. That should make them invisible to the naked eye. SpaceX is also working on better CCDs for large telescopes that aren't as effected by satellites -- any satellite, not just starlink. In theory, they could remove power to individual pixel sensors at the moment that you know that they will be looking at a satellite. At the very least they could fix the problem with current sensors where a single saturated pixel screws up an entire row or column of pixels.

For more info, see [17] and [18]. --Guy Macon (talk) 07:23, 26 June 2020 (UTC)[reply]

Thanks. I can't see magnitude 5.5 anyway, but I could see them when they were between 3 and 4. Bubba73 ^{You talkin' to me?} 21:50, 26 June 2020 (UTC)[reply]

It's a fascinating engineering problem. To avoid overheating, a satellite should be white or shiny. To avoid being seen it should be flat black. Except you don't get to choose the color of the solar cells. The shades can be flat black because we can easily make them so they don't get damaged if they get hot. We should also try to make the shates thermal insulators so that the back side isn't a glowing light source in the infrared illuminating the satellite. That makes the front side even hotter, though, changing the color temperature and intensity of the IR coming from the front of the shade. But if the front side points way from the earth, who cares? Except that there are telescopes in orbit. Now to add another complication: it isn't just the sun that shines light on a satellite to be reflected. It also experiences moonlight (varies with the phase and position of the moon) and earthlight (varies with amount of cloud cover and time of day). So many variables to juggle! --Guy Macon (talk) 13:14, 27 June 2020 (UTC)[reply]

This one has me perplexed. The National Bureau of Economic Research published a paper regarding the spread of covid-19 among BLM protesters. The paper has received coverage from the mainstream press.[19] As best as I can tell, the National Bureau of Economic Research is a respected, peer-reviewed journal. However, their field of expertise appears to be economics, not health care. I would think such an article would be reviewed and published by a medical journal, not by an economics journal. Am I correct in thinking that they published an article outside their field of expertise? Is so, is this frowned upon within the scientific community? A Quest For Knowledge (talk) 07:12, 26 June 2020 (UTC)[reply]

I don't think it matters. "NBER working papers are circulated for discussion and comment purposes. They have not been peer-reviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications."

It looks like the Center for Health Economics & Policy Studies at San Diego State University got a grant from the Charles Koch Foundation and the Troesh Family Foundation to do this study, and CHEPS chose NBER as a venue to put it out without peer review. One would hope that they have plans to submit it to a peer-reviewed journal in the future. Until they do it fails WP:MEDRS. --Guy Macon (talk) 07:32, 26 June 2020 (UTC)[reply]

Thank you for the informative answer. I wasn't planning on using it in an article. I just found it curious that economists are publishing articles about medical issues. A Quest For Knowledge (talk) 18:02, 26 June 2020 (UTC)[reply]

I'm having trouble finding this fairly simple info (in Wikipedia or elsewhere). For the just-recently concluded Solar cycle 24 and during the associated solar minimum, which direction is/was the Sun's overall dipolar magnetic field pointing in relation to the Sun's rotation axis? (For comparison, the Earth's magnetic field is currently pointing (mostly) in the opposite direction of the Earth's positive rotation vector, since the magnetic pole in the Arctic is actually a "south-seeking" pole.) Also, is it safe to say that the conclusion of every previous even-numbered cycle (22,20,18,16,...) had this same polarity? DWIII (talk) 07:49, 26 June 2020 (UTC)[reply]

The Sun's polar field reversals are out of phase with our way of segmenting sunspot activity in cycles: these reversals occur during the cycle maximum, halfway each cycle. (You could say instead that our way of segmenting is out of phase with the Sun.) As far as we know and understand these solar cycles, they are driven by the polar field and its reversals, so it is a safe bet that as long as the Sun does not do something unexpected like a double somersault, the polarity change during a cycle goes the same way for cycles whose numbers have the same parity (and the opposite way for the others). There appears some uncertainty, though, whether 1784–1799 was one unusually long cycle, or two unusually short cycles, so going back all the way to the 18th century the bets are off. Figure 22 in the paper "The solar cycle" shows that the field flipped from positive polarity north pole to negative polarity north pole during the maximum of cycle 23. So it should have flipped the other way during the maximum of 24, meaning that right now the Sun has positive north pole polarity. The paper linked to is an overview of about all that is known about the solar cycle.  --Lambiam 07:17, 27 June 2020 (UTC)[reply]

Thanks(!); that source is definitely informative. So, I take it that, by convention, "positive polarity north" is synonymous with "north-seeking magnetic pole aligned with geographical north", meaning that the dipole magnetic fields of the Sun and the Earth are currently (as of 2020) pointing in opposite directions (coincident with the end of cycle 24 and the beginning of 25). The primary reason I asked is that, while Earth's magnetic field direction is indicated through geologic time in the geomagnetic reversal article, there doesn't seem to be any mention of specific polarities in the main solar cycle article article, or even in any of the individual solar cycle articles. Yes, there is that blue-yellow graphic which seems to indicate polarity over the last four cycles, but it's not at all clear that "yellow = magnetic north". DWIII (talk) 16:38, 27 June 2020 (UTC)[reply]

With the existing confusion (the North Magnetic Pole, often referred to as the "Magnetic North Pole",^[20][21] is a magnetic south pole} I wasn't too sure about the convention in solar science, so I just copied the terminology of the paper without attempting to interpret it. As this book observes, these terms can be very confusing when applied to the Sun. (Unfortunately, the treatment in that book does not do much to quell the confusion.) Customarily, the "positive" pole of a magnet is its north-seeking pole.^[22][23][24] I assume the paper uses the same convention when using the term "positive polarity".  --Lambiam 20:07, 27 June 2020 (UTC)[reply]

When one reads about dietary supplements such as Iron, e.g. "...Brussels sprouts are rich in iron..." is this the same substance as Iron such as cast iron bridges are made out of? I have read the article but I am still unclear. Thank you. — Preceding unsigned comment added by 86.162.76.127 (talk) 09:27, 26 June 2020 (UTC)[reply]

• Yes, and no. (Helpful, heh?)

If you have a solid grasp of chemistry already, a link to our article Human iron metabolism might be all you need. If you remember the basics, read on. And if you forgot even the high-school classes, I give a quick summary in the box below.

Iron atoms are indistinguishable and thus, at the atom level, iron in a bridge and iron in a vegetable are identical. However, those iron atoms can exist within different molecules.

Bridges are usually made of steel or cast iron, that is a crystalline structure of pure iron with some carbon atoms sneaking inside the holes of the structure, forming an interstitial alloy. (Cast iron = high-carbon steel; "crystalline" = periodic ordering of atoms.) In a bridge, we do not want the iron to be oxidized in the Fe2O3 form by oxygen in the air; that phenomenon is called rust and must be avoided (usually by paints that do not let oxygen through).

On the other hand, humans do not usually eat chunks of metal. Human_iron_metabolism#Dietary_iron_uptake says that iron crosses cell walls in the Fe2+ form (see this article for details) and that enzymes can reduce the Fe3+ form into Fe2+. I suppose (but could not find a proper source for that) that most if not all of iron in edible food is in ionic compounds such as Fe2O3. Notice also that only a fraction of iron in the food makes it through the digestive tract, and that amount may also depend on cooking procedure.

Hence, the molecules and chemistry for both cases are significantly different, even though the atoms are the same.

I would also add that the largest part (probably more than 90%) of the "dietary supplement" industry is a giant scam selling health dreams to misinformed consumers. Iron deficiency is real (unlike other deficiencies advertising would have you correct with their products), but do not buy iron supplements on your own (and definitely do not lick metal scrap pieces!). Go see your doctor and buy supplements only if they so prescribe (and then, buy what they prescribe, even if some TV salesman tells you that their supplement has "four times the iron intake of others" or whatever). Most likely, if you are not at immediate risk of anemia or another iron-deficiency-related disease, they will suggest diet changes rather than supplements. Tigraan^{Click here to contact me} 10:44, 26 June 2020 (UTC)[reply]

Thank you and, WOW! what great answers. It is really appreciated. Now I know. BTW, the reason for asking was that an acquaintance suffers from high iron and has to donate blood on a regular basis as a lifelong cure. Without this he freezes and goes stiff and faints. Not a medical question, but pure intellectual curiosity. — Preceding unsigned comment added by 86.162.76.127 (talk) 12:14, 26 June 2020 (UTC)[reply]

It is very common for chemical elements to be listed as the constituents of commercial products when, in fact, the product contains compounds of the elements, not the elements in the pure state. For example, many garden fertilizers come in packaging that specifies it contains nitrogen N which is a gas at room temperature and pressure. The fertilizer contains compounds of nitrogen, not nitrogen gas. Similarly, fertilizers are stated to contain phosphorous P which is a rather hazardous substance in its pure state. What the fertilizer contains is one or more compounds of phosphorous and those compounds are not hazardous. Similarly with potassium K, a dangerously reactive metal in its pure state. So when I see a statement that a food is rich in iron Fe I assume the statement is actually referring to one or more compounds of iron. Dolphin (t) 12:52, 26 June 2020 (UTC)[reply]

In the same vein, see Louisville Waterfront Park, where a sign was posted warning visitors tempted to dip in the fountain that the water "contains high levels of hydrogen". I am both admirative of a great user design idea and sad that it works better than "please do not bathe in the fountain" (or at least was expected to work by someone whose job it is to design such warnings). Tigraan^{Click here to contact me} 15:01, 26 June 2020 (UTC)[reply]

I bet a chemical analysis would show the presence of dihydrogen monoxide (DHMO) in that fountain.  --Lambiam 19:48, 26 June 2020 (UTC)[reply]

Except maybe in the dry season. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:03, 26 June 2020 (UTC)[reply]

Re "It is very common for chemical elements to be listed as the constituents of commercial products when, in fact, the product contains compounds of the elements, not the elements in the pure state", whenever I see "low sodium" on a food package, I think "I certainly hope so!"   :)   --Guy Macon (talk) 11:01, 27 June 2020 (UTC)[reply]

A common grade school science project involves magnetically separating from cereal the powdered iron filings added for fortification. See this short (0:58) BBC Science Focus Magazine video: How to extract iron from cereal^[YouTube]. -- ToE 13:04, 27 June 2020 (UTC)[reply]

Is this article correct in saying that ferrite cores are significantly lossy below a certain frequency range, and if so, then what's the explanation for that fact? I (think) I understand why it's true for frequencies above a certain range (due to hysteresis and eddy currents). ZFT (talk) 19:07, 26 June 2020 (UTC)[reply]

Hysteresis is a more significant loss factor at lower frequencies. See here (page 154 in the chapter; section "Core Losses"): "• At low frequencies, ferrite core loss is almost entirely hysteresis loss."  --Lambiam 19:42, 26 June 2020 (UTC)[reply]

June 27

Describe about cell division -- Ganga Basnet (talk · contribs)

Have you read our article Cell division? If that does not answer your question, can you be more specific about what you want to know?  --Lambiam 07:24, 27 June 2020 (UTC)[reply]

If all kinds of matter is made up of atoms, including biotic and abiotic substances. Then living organisms and non-living substances must have been made up of same atoms. like biotic organisms are made mostly up of carbon molecules,and on the other hand coal is made up of the samecarbon molecules. Then why there is a difference between living organisms and non-living substances? -- 117.209.175.248 (talk · contribs)

Read Life for some possible insight. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:10, 27 June 2020 (UTC)[reply]

The simple answer is that it all depends on how these atoms are arranged, first into molecules, and then how these molecules are connected and interact, not only chemically but also mechanically. A cooking pot and a vacuum cleaner are made up from the same kind of atoms, but you cannot use a cooking pot for vacuuming or a vacuum cleaner for cooking. A vacuum cleaner is much more complex than a cooking pot; it is composed of a collection of components that have to be combined and connected in specific ways for the vacuum cleaner to function. But both cannot function without an external source of energy; heat for the cooking pot and electricity for the vacuum cleaner. Living organisms are much more complex than vacuum cleaners, but they too consist of a collection of components that have to be combined and connected in specific ways for the organism to function. And then they too need a source of energy.  --Lambiam 14:39, 27 June 2020 (UTC)[reply]

It is not correct that "biotic organisms are made mostly up of carbon molecules". They (we) are made of molecules most of which contain carbon. For a simple example, glucose has the formula Template:Chemical formula, meaning that each molecule contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. To be glucose rather than some isomer of it, the atoms also have to be arranged in a specific way. If a substance contains only carbon atoms, then it's coal or graphite or diamond or a fullerene, depending on how the atoms are arranged. --76.71.5.208 (talk) 21:56, 27 June 2020 (UTC)[reply]

What are the practical (i.e., explained in a way, if possible, without relying solely on mathematical statements) differences between these units? Specifically, what are the physical effects, on objects in a magnetic field (including the object generating the field), of changing the value of any one of these units? ZFT (talk) 20:48, 27 June 2020 (UTC)[reply]

As a start, let's look at Weber (unit): "In physics, the weber (/ˈveɪb-, ˈwɛb.ər/ VAY-, WEH-bər; symbol: Wb) is the SI derived unit of magnetic flux. A flux density of one Wb/m² (one weber per square metre) is one tesla." (refs omitted) So a weber is a total amount and a tesla is how concentrated or intense it is in a given area. That's like you can stand your whole weight on a bed of needles because your weight is spread over a large area (not much pressure on any one needle) but if you concentrate that same weight focused by standing on a single needle, yeeeeouch! Or if one nail can only hold up a certain-weight object on your wall, you can get more total weight held by using more nails. DMacks (talk) 21:26, 27 June 2020 (UTC)[reply]

June 28