October 27

Are there any foods that have never lived? Meaning, no animals, plants bacteria etc. Would it be possible to live on such diet? -- 193.64.221.25 (talk · contribs)

Water... most people might last a few weeks. Roger (Dodger67) (talk) 06:18, 27 October 2017 (UTC)[reply]

Only prokaryotes can do that, they have the enzymes to take in abiotic chemical compounds and make all the stuff they need. Eukaryotes are dependent on other organisms for their survival, e.g. they can't make vitamin B12, they don't have the enzymes for nitrogen fixation either, so they are dependent on prokaryotes for their amino-acids. Count Iblis (talk) 06:32, 27 October 2017 (UTC)[reply]

It is possible to make synthetic fatty acids [1] - mercifully, it doesn't seem to have caught on; I guess the odd-numbered ones did not even meet up to the standards of the trans fat era. Synthetic sugars are harder. [2] Vitamin supplements are an issue, yet some are produced synthetically. There is no theoretical reason why such a diet cannot be produced (though you might need to go off-planet to find carbon you are somewhat confident 'never lived'), but it would be exceedingly difficult, so I would not expect the first test subjects to live long. Also note that ethane, present on Titan, is metabolized by the rat [3] so at least some "foods" presently exist that match this criterion, though it would be poorly nutritious and a bit over-chilled on the palate. Wnt (talk) 11:03, 27 October 2017 (UTC)[reply]

There are many kinds of extremophiles that live on, for example, organic chemicals that seep into the oceans from mid-oceanic hydrothermal vents. Chemosynthesis would be the term. As to the main question, no, it is not possible for you as a person to live on food which has never lived. Excepting certain dietary minerals, which do not provide energy to your body, food entails life. All food must have been living at some time previous, for any reasonable definition of "previous". Some foods are currently living. Indeed, many raw plant foods we eat are alive while we consume them. --Jayron32 11:06, 27 October 2017 (UTC)[reply]

Can we say that plants have a diet of non-living food? I mean they just need water and minerals from the ground, CO2 in the atmosphere, and sunlight for energy. I guess the question is more about whether you accept that plants "eat" at all.— Preceding unsigned comment added by Lgriot (talk • contribs)

Well, that's it. We need to define "eating". I mean, I would define that as ingesting a substance for the purpose of obtaining energy and building materials. There are other forms of ingesting we do (drinking, smoking, taking medicine or vitamins) which we don't call eating. Wikipedia's article on eating specifically excludes most plants, since plants are autotrophs. If you change the definition of eating, then sure, you can define plants as eating. But really, if you can just change the definitions of words to fit your needs, you can "prove" anything with those words. --Jayron32 14:42, 27 October 2017 (UTC)[reply]

Note that plants depend on bacteria to do the nitrogen fixation necessary to make amino acids. Count Iblis (talk) 18:00, 27 October 2017 (UTC)[reply]

The answers to a similar question from 2014, Wikipedia:Reference_desk/Archives/Humanities/2014_August_14#Non-living_food, may be of interest.--Wikimedes (talk) 18:39, 27 October 2017 (UTC)[reply]

There aren't any foods currently consumed that have never lived, but it would be possible in principle in make some. Probably the easiest, as far as I can tell, is ethanol -- which in spite of its use as an intoxicant is actually a high-calorie food source. Other edible foods can be made by artificial photosynthesis or chemical synthesis, for example simple sugars such as glucose, but the process is very expensive. Looie496 (talk) 21:14, 27 October 2017 (UTC)[reply]

@ Looie496 What about milk and honey? 185.217.68.208 (talk) 07:14, 30 October 2017 (UTC)[reply]

There are many minerals which, by definition, are produced by inorganic processes. Sodium, iron, calcium, potassium, etc. These are essential parts of the diet, but obviously not sufficient alone. Of course, just like with carbon, they may have been part of a living organism at some point in the past. StuRat (talk) 22:50, 27 October 2017 (UTC)[reply]

• The relevant article is abiogenesis. Even if you hold the fringe panspermia theory, the first life to arise (or "arrive") here on Earth was, pretty much by definition, bathed in a sea of free, simple organic nutrients. Last universal common ancestor describes an organism that derived its energy using chemiosmosis, but this organism would have been quite a bit more sophisticated than the first living protocell. μηδείς (talk) 18:31, 29 October 2017 (UTC)[reply]

• See chemoautotrophy. There are archea at deep ocean vents that "eat" only inorganic chemicals that come out of the earth. This is not "food" for you or me, but it is for them, and is probably the only known thing that roughly counts as an answer to your question. SemanticMantis (talk) 18:52, 29 October 2017 (UTC)[reply]

I think hydrothermal vent nutrients may not be seeing the biosphere for the first time. My impression of the biogeochemistry of volcanism is that often magma is released relatively rapidly from descending subduction zone material. I would not, however, be ready to guarantee that is always true. Wnt (talk) 02:23, 31 October 2017 (UTC)[reply]

October 28

I was reading different sources about the number of the N-receptors (nicutinic receptors) among the cholinergic receptors. The most of the sources say that there are 2 nicutinic receptors (N1 and N2) but other source says there are 3 nicutinc receptors: "Nicotinic receptors are found in the CNS, in autonomic ganglia, and in striated muscle. They are divided into N1, N2, N3-cholinoreceptors. N1 - and N2 -cholinoreceptors are localized in the CNS, N1 -cholinoreceptors – in ganglia, N2 -cholinoreceptors – in muscular synapses, N3-cholinoreceptors – in the adrenal glands. The mechanism of nicotinic action has been clearly defined." Is that correct?--212.90.60.81 (talk) 04:08, 28 October 2017 (UTC)[reply]

We have a detailed article about Nicotinic receptors (note spelling). It categorizes them into two major groups based on location—muscular vs neuronal—and then further into ganglion-type and CNS-type of neuronal. It not mention a type specific to adrenal-gland location and does not use N1/N2/N3 terminology at all. Could you cite the source you are quoting so we can see context and if it cites other refs for us to read? DMacks (talk) 04:25, 28 October 2017 (UTC)[reply]

• If you want other sources than our article, see "Mammalian Nicotinic Acetylcholine Receptors: From Structure to Function", most recent review I could find in two minutes on PubMed. Look at tables 1 and 2. Fgf10 (talk) 10:30, 28 October 2017 (UTC)[reply]

This comes from the 19th-century book that I referenced in the toothache question of Wikipedia:Reference desk/Archives/Science/2017 October 8. I've got someone born in 1811 who moved to Iowa in 1851 and lived there until his 1880 death, and about him it's said:

The exposure which he was required to endure in a new country and among scattered societies, caused inflammatory rheumatism, which completely wrecked his physical frame, and the last ten years of his life were spent in intense bodily suffering.

Can the environment or physical exertion cause rheumatism of any sort? Apparently it can't cause rheumatoid arthritis, since Rheumatoid arthritis#Risk factors for this autoimmune disease are all irrelevant for a preacher in 19th-century Iowa who rejected drinking and smoking as sinful. I'm guessing that our Iowa friend got some sort of illness along the way (per the first sentences of Rheumatism#Types), or that he had an autoimmune disease that simply started after he moved. Is this a reasonable conclusion? Nyttend (talk) 13:16, 28 October 2017 (UTC)[reply]

I think the article rheumatism is pretty clear -- it's a generic term for pain. Serious physical exertion might cause osteoarthritis, either directly or as the result of physical injury to the joints. Damage to the sacroiliac joint or to the spine itself might cause sciatica or related conditions. There are a lot of options and I certainly can't diagnose a sentence (and am not qualified to diagnose a patient either). But going from rheumatism to rheumatoid arthritis specifically seems like a vulgar error. Wnt (talk) 15:19, 28 October 2017 (UTC)[reply]

Without knowing where this unfortunate person was and the nature of the terrain, it's impossible to even guess. It's possible it might have been what we now know as Lyme disease. When I received the diagnosis of RA, I was told that there are hundreds of conditions that all get lumped together as "rheumatoid arthritis" for ease of discussion. What might shed light on whether it was rheumatoid arthritis is a trace of his descendants and looking at their medical history, to see if any of them had rheumatoid arthritis or not. (OR here, well it's not my research but... I am currently taking part in a clinical trial to establish the degree of hereditability of RA, and as part of that, I have found this horrible disease seems to have affected at least 4 out of the past 6 generations of my family, up to and including myself.) --TammyMoet (talk) 10:42, 29 October 2017 (UTC)[reply]

Assuming it was genuine, approximately how many years it took for Wow signal to reach the Earth? If there's an RS, one might want to add it to the article. Thanks--212.180.235.46 (talk) 17:44, 28 October 2017 (UTC)[reply]

Depends on which star it (might have) come from. The article on Wow says that the closest easily visible star in the direction of Wow is Tau Sagittarii. The article on that star says that it is 122 light years away. But that is just a possible answer to your question,!of course. Attic Salt (talk) 17:54, 28 October 2017 (UTC)[reply]

And, in case it's not obvious, it would take a signal 122 light-years away 122 years to reach us, at the speed of light. StuRat (talk) 16:02, 29 October 2017 (UTC)[reply]

Part of the problem and mystery of the Wow signal is that the receiver wasn't really pointing at any nearby stars when the signal came in. Tau Sagittarius is the closest easily visible star to where the signal came from, but that means "closest" from our perspective. Closest if the heavens were a flat image.

If you look at the map on the Wow signal article, it came from one of the two red ovals on the star chart. (It was received by a pair of receivers, but the way they filtered the signal means they don't know which of the two receivers actually picked up the signal.) The red ovals are a bit to the north-west of Tau S.

If the signal really is extra-terrestrial and our data about it is correct, then either it came from a transmitter in deep space (a starship?) or it came from a star system incredibly far away. Much farther than Tau S. ApLundell (talk) 15:52, 30 October 2017 (UTC)[reply]

October 29

Are there any cases in which cis-trans notation would still be ambiguous if -cis- and -trans- were used as infixes before pairs of substituents? For example, (Z)-1-Bromo-1,2-dichloroethene could just be called bromotransdichloroethene. (Note the advantage of also being able to eliminate the numeric infixes in that case, since 1,1-dichloro wouldn't be transdichloro.) Likewise, the haloalkene with SMILES C(/Cl)(\Br)=C/F would be 1-chloro-cis-1-bromo-2-fluoroethene. NeonMerlin 11:59, 29 October 2017 (UTC)[reply]

I think it is hard to answer this sort of "why didn't they do it like that?" question. The rules used have some arbitrary components. At this point though, practically, suppose someone introduces your rule. What does it mean? Well, sometimes you can use it, sometimes you might use it, often you would encounter things labelled with E/Z notation. So it means we have to learn your scheme and how to apply it to compounds like [4] with four different kinds of atoms attached to the double-bonded carbons (which is actually not recommended according to our cis-trans article) and whether the "cis" applies to the thing directly after it or the two things in the "di" or ... whatever. And then we also have to be ready to understand E-Z notation. Which amounts to more trouble to learn, more entries in the tables of synonyms in a PubChem entry (exponentially more, since this permutes with every other arbitrary decision we make between naming systems), more errors. I think many people would not be pleased to encounter this kind of creativity in their chemical closets. Wnt (talk) 15:52, 29 October 2017 (UTC)[reply]

This explains situations where cis-trans is different from Z-E. Cis-trans is a subset of Z-E notation, such that all cis are Z and all trans are E, but the inverse is not true. The Z-E notation, it should be noted, is formal IUPAC convention, where as cis-trans is more informal (i.e. the difference between "ethanoic acid" and "acetic acid") As noted, there is no meaningful way to answer a question "why didn't they". Because they didn't. This is the system. --Jayron32 12:18, 30 October 2017 (UTC)[reply]

Your first statement is not true either. Trans-2,bromobut-2-ene is (Z)-2,bromobut-2-ene, because the groups with the higher priority on each end of the double bond are CH₃ and Br respectively. So the E-Z convention compares the CH₃ and the Br, while the cis-trans convention compares both CH₃ groups, producing opposite results. Double sharp (talk) 13:04, 30 October 2017 (UTC)[reply]

Even more reason why there are two systems. Thank you, Double Sharp! Well answered! --Jayron32 13:23, 30 October 2017 (UTC)[reply]

Thank you!

As for the OP's original question: in principle, you could indeed build a consistent system this way. However, (1) it's not used by anyone, and (2) it seems to be more problematic to decode because cis and trans only encode relative stereochemistry, whereas E and Z use an absolute frame of reference from the priority rules, as can be seen from my previous example. But you can certainly be the judge: try decoding the molecule name (4E,6Z)-1,1,7-trichloro-4,6-dimethyl-1,4,6-nonatriene (an example I got from the wonderful resource Master Organic Chemistry), and then try writing its name under your proposal. I think you'll find that the need to constantly shift your frame of reference in the relative nomenclature and nest the "cis" and "trans" in such a case is not worth the backward compatibility for the simple cases. Double sharp (talk) 14:51, 30 October 2017 (UTC)[reply]

There is no direct reference to J. E. Hogarth in Wikipedia, or the WEB, except for indirect links that cite his published work as for example in Stephen Hawkings dissertation. Why is this?

Is he notable in the Wikipedia sense? If he is, then he will have been written about elsewhere (try libraries if not on the web), and if not then he doesn't merit an article here. Dbfirs 16:38, 29 October 2017 (UTC)[reply]

I think maybe not? Here [5] is all the records for JE Hogarth on Google Scholar. Many of those are clearly not a guy who Hawking would be citing in his dissertation. His most notable work is published in Proc. Roy. Soc. A in 1962 (PDF here [6], it's about the arrow of time, among other things, and it seems the sort of cosmological thing that Hawking would have been interested in. It has attracted only 130 citations since then. Now, bibliometrics alone cannot establish or rule out notability on their own, but honestly, that's just not a very big impact (e.g. I have a paper with around that many citations published in 2011, and I'm a total nobody as far as WP notability is concerned, even if a few famous folks have cited my work).

Other than that, I can see a record of his dissertation and abstract [7], and that he was an editor for a few years [8] for the Ontario Association for Mathematics Education, and a member of the Canadian Mathematical congress [9] SemanticMantis (talk) 18:47, 29 October 2017 (UTC)[reply]

If you search Google Books rather than Google Scholar, you will find at least one that describes his work rather extensively, so I think he meets the notability criteria. The real problem is that hardly any information about him. He was in the Math Department at Queen's University in Ontario for many years, and has children living in the area, but that's basically all I can find out about him. He doesn't seem to have published anything significant after 1963. Looie496 (talk) 18:53, 29 October 2017 (UTC)[reply]

From what is accessible using Google, the most detailed might be this. Curiously, or ambiguously it states: "Although Hogarth only published his analysis in 1962, it was generally known to many people before that time." I think there is mention of a thesis of him dated 1953, if that is correct I would be curious to know what was the situation precisely between 1953 and 1962. --Askedonty (talk) 19:37, 29 October 2017 (UTC)[reply]

I suppose it could go either way. For this kind of guy, we'd have to specifically apply Wikipedia:Notability_(academics)#Criteria, not just general notability standards. Maybe his "research has had a significant impact in their scholarly discipline", but that seems a little odd given his frankly thin publication and citation counts. Then again, it's quality not quantity that counts, so perhaps the book you mention could be used as an RS to demonstrate significant impact. SemanticMantis (talk) 14:32, 30 October 2017 (UTC)[reply]

October 30

What is the highest thermal efficiency ever achieved by a steam locomotive? I know their typical efficiency is only 5-10%, yet I've read somewhere that some of them (notably some of the later French De Glenn compounds) achieved an efficiency of up to 25% (at the cost of greatly complicating both operation and maintenance) -- is that true? 2601:646:8E01:7E0B:65AB:303D:F2EB:232 (talk) 06:16, 30 October 2017 (UTC)[reply]

Locomotive engines in particular face severe practical limitations that reduce their efficiency. Even battleships had to make some compromise in their reciprocating steam engines, for example few if any used quad expansion expansion engines. Even so the efficiency of their massive engines maxed out at 13%. Derived from "Ship Form, Resistance and Screw Propulsion" by GS Baker, published in 1920. So how could the necessarily compromised railway locomotives get double that? By going to a steam turbine possibly. But that incurs losses in the transmission. I suggest you challenge the 25% figure, it doesn't pass the sniff test. Greglocock (talk) 06:44, 30 October 2017 (UTC)[reply]

Coincidentally the highest efficiency I can find for a Andre Chapelon design is 12%. Greglocock (talk) 06:55, 30 October 2017 (UTC)[reply]

And 12-13% for Argentina https://static1.squarespace.com/static/55e5ef3fe4b0d3b9ddaa5954/t/55e637bee4b0bef289260255/1441150910433/%23+DOMS-2_PORTA_Argentina.pdf Greglocock (talk) 07:09, 30 October 2017 (UTC)[reply]

• The most efficient weren't the French de Glehn's, but rather Chapelon's larger 8-coupled locos, the 242 A 1 and 240P. Another couple of engineers worth looking at L.D. Porta in Argentina and David Wardale's Red Devil in South Africa. Much of this later work wasn't about thermal efficiency so much as improved mechanics (the developing technology of the time was offering useful developments here, such as roller bearings), and in more efficient combustion with worse fuels. Porta's Gas Producer Combustion System in particular. Koopmans. The Fire Burns Much Better. ISBN 1909358053. is an important text in this field.

A steam locomotive is first of all a locomotive: it has to move itself, it has to fit through the railway loading gauge. This has always been a limitation on their performance and the sophistication possible. As a result they always lagged behind marine and stationary engine practice. High boiler pressures, steam turbines, condensing and even superheating either didn't appear on locomotives or only later and with less success. Turbines in particular were a notable failure owing to the lack of a successful high pressure watertube boiler and the only one that was adequately reliable was the Turbomotive, the least technically adventurous of them. Andy Dingley (talk) 11:01, 30 October 2017 (UTC)[reply]

I found a project to rebuild a 1956 locomotive, ATSF 3463, to run on torrified biomass. The modernised boiler arrangement is being claimed to double the original thermal efficiency, although there is much scepticism [10]. Alansplodge (talk) 17:16, 30 October 2017 (UTC)[reply]

Whatever the peak efficiency was, it was likely "topped" by the DR 18 201. Unfortunately for you it was not common in the steam engine technology to measure efficiency in "%". Never the less i doubt classical steam engines can manage more than 10%, because they only use the pressure part of the total thermal energy and even that rather unefficient. Steam turbine systems in power stations can reach up to 45% but these are huge, stationary cyclic systems with buid investments of up to 1 billion $, so its sure that these are all state of the art in peak efficient at the time they where build. --Kharon (talk) 01:30, 31 October 2017 (UTC)[reply]

A rather out-of-sequence one-off loco, not particularly fast (182.4 km/h or 113.3 mph is not exceptional for steam locos) and designed in its day just to be fast enough to test new coaching stock (see the MÁV Class 242 too). It's notable today for having been preserved, not for its speed. There's no indication that it was ever especially efficient. Andy Dingley (talk) 11:28, 31 October 2017 (UTC)[reply]

I was intrigued by the question above. Unless I missed some nuance in the question, my immediate thought was "milk and honey". Neither of these has ever "lived". Sure they were produced by living creatures but they in themselves are not considered alive. Would this fit the OPs question? 185.217.68.208 (talk) 07:12, 30 October 2017 (UTC)[reply]

You'd have to ask the OP (193.64.221.25 (talk · contribs)) that question. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:31, 30 October 2017 (UTC)[reply]

Both of those things are mode from living things.

Honey is made from pollen. Pollen was certainly once alive.

Milk is less obvious, but it must ultimately came from whatever the cow ate. (Probably grass? Or corn?)

Of course, as Bugs points out, you'd have to ask the guy who wrote the original question if that "counts" for his purposes. ApLundell (talk) 20:50, 30 October 2017 (UTC)[reply]

Yes. It would be nice if he would come back here and Finnish. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:05, 31 October 2017 (UTC)[reply]

What data sources are available for the density of moist ordinary salt (sodium chloride) samples as a function of water content and perhaps porosity or void fraction? (Thanks)--82.137.11.59 (talk) 10:43, 30 October 2017 (UTC)[reply]

At Manley’s Technology of Biscuits, Crackers and Cookies you can see the bulk density of granular dry salt 1.22 to 1.32. Using this and the density of sodium chloride crystals of 2.165, you could work out the void space that could contain water and then work out how much water would add what weight, and so get a new density for damp salt. See Bulk density to read about issues to do with density. Graeme Bartlett (talk) 12:02, 30 October 2017 (UTC)[reply]

It's not quite that simple, because some of the water will dissolve some of the salt and form a saturated brine. Because of this, the relationship is likely to be highly non-linear, and just a raw calculation of "filling the void space with water" is unlikely to work; it would work for an insoluble solid like sand, but for salt it gets quite messy to work it out by calculation. You could get a number assuming simply filling in the void space; but that number would bear little connection to the actual denisty. --Jayron32 12:12, 30 October 2017 (UTC)[reply]

Perhaps predetermining porosity of dry solid salt with liquids like mercury would be a workable variant? Or perhaps checking the plausibility of the assumption that solid dry salt has near zero porosity? An other aspect I think it should be considered and had in mind when formulating the above question is water activity in humid solid salt! I have put the question mainly to address the issue of water activity in this solid substance and to check the degree of non-ideality of the water salt solid mixture as non-ideal solution!

Considering these aspects, another question arises: How can the brine content in the possible void spaces in solid salt be determined?(Thanks)--82.137.14.216 (talk) 13:35, 30 October 2017 (UTC)[reply]

Sodium chloride, thankfully, has a relatively flat solubility curve, so the density of saturated brine is fairly constant at all temperatures from the freezing to the boiling point, 1.202 grams/mL That may be useful. --Jayron32 15:37, 30 October 2017 (UTC)[reply]

Salt is expected to be sold dry. Normally it does not absorb water from the atmosphere unless it is very humid.[11] The density of bulk depends on how it is handled.

Isn't the rate of change in density with respect to the propotion of water a linear relationship at constant temperature and pressure, in the special case where the solution is saturated? Should the density lie on a straight line between the density at a concentration of 359 g/L and the density of pure salt at 2.165 g/mL? It could also depend on a energy minimum, whether or not the system has an energetic preference for a certain amount of water to be incorporated. Plasmic Physics (talk) 19:23, 30 October 2017 (UTC)[reply]

For some reasonable definition of coastline and ocean. I always liked "where mean water level = mean sea level". Do small islands change the answer much through sheer numbers and often being far offshore where tides are smaller? Sagittarian Milky Way (talk) 14:03, 30 October 2017 (UTC)[reply]

There may be a real number for this, but I can't find anyone that has actually calculated it. I've checked several likely google searches, and I can't find anywhere that anyone has ever calculated a worldwide mean tide. The variation is highly dependent on where and when the tide is measured. Hypothetically it may be calculable. Realistically, I can't find any reference to help you figure it out. --Jayron32 15:35, 30 October 2017 (UTC)[reply]

Sorry, maybe I'm just being dense. Are you asking about the average (mean) difference in height between high and low tide, based on the sample of all the coastlines in the world? The coastline paradox still comes back to bite you, right? Whatever unit you use to determine how many points to measure (every x miles or millimeters of coastline) will affect your answer with the added bonus that the tides also affect some portion of river's edge deeper inland (as with a tidal bore). Matt Deres (talk) 16:31, 30 October 2017 (UTC)[reply]

• far offshore where tides are smaller - I would have thought this was "obviously" wrong because outside of areas where water flow is restricted (e.g. Gibraltar is a small passage to the Mediterranean Sea), sea level would simply follow the equipotential of gravitational energy (IIRC if you assume two point-like masses at the centers of Earth and Moon, it is an ellipse). It turns out that is not the case (example: the Azores have much less tide than Lisbon at the same latitude).

This and that indicates that the tide level is a matter of forced oscillation of the water masses in the ocean basins. It is therefore unlikely that there is an easy way to compute tide height at any given location.

You could pull a database of historical tide heights at a lot of locations where that is measured and average them, hoping that it gives a good proxy of the average tidal height (it probably isn't; for instance, ports are at places where tide is low and measurements are done where people are interested to have the data i.e. at ports). I was initially hopeful to find this in a reasonable format for free on the web, but my enthusiasm dissipated after reading this. The closest I found is [12] but that is a pdf format probably impossible to feed to a program. Tigraan^{Click here to contact me} 18:31, 30 October 2017 (UTC)[reply]

An OCR program could pull (digitize) the tide data from the pdf tables but the same data is more readily available ready digitized at [13]. Coastlines may be drawn at Mean High Water (on maps and charts), at Mean Sea Level (on maps showing sea depth) or at Lowest Astronomical Tide (on nautical charts), see Tide#Definitions. Harmonic analysis of tides was introduced in the 1860s by William Thomson (titled "Lord Kelvin" after the river near his laboratory) who built impressive mechanical Tide-predicting machines that employed Ball-and-disk integrators. Harmonic analysis offers the means to subtract all the oscillatory terms of a long-term (19-year, see Metonic cycle) Fourier series analysis to leave only the zeroth term corresponding to the mathematical average. Tidal prediction data thus obtained were kept secret during WW1 and WW2, which is understandable, were then made public, but then in the USA were removed from the public domain after the fact by SCOTUS in Golan v. Holder in 2012 - a ruling on which the WMF in collaboration with the EFF had words to say. Blooteuth (talk) 20:15, 30 October 2017 (UTC)[reply]

As I understand it, and this seems to be supported by our article, Golan v. Holder did not remove anything from the public domain. It simply affirmed the removal from the public domain by the Act in question. Quite a few parties felt the removal was unconstitutional in some way, but few disputed that the Act in question claimed to do so. Incidentally, please remember that there is a difference between something being in the public domain, which generally refers to copyright and definitely does in the court case in question, and whether something is a classified/secret or public information. (Both can restrict access to information in various ways, but the manner of these restrictions is often quite different, hence they are not normally treated the same.) Nil Einne (talk) 06:34, 31 October 2017 (UTC)[reply]

Note that while mean and median aren't the same, mathematically, they may work out to be similar in the case of a sinusoidal wave, like tides. See measures of central tendency. StuRat (talk) 04:16, 31 October 2017 (UTC)[reply]

When Voyager 1 runs out of power and we develop manned space travel past our planet's orbit, how easy will it be to find Voyager 1 to study it? I realize this is sort of crystal balling but maybe someone has thought of it before and did some research. †dismas†|^(talk) 18:34, 30 October 2017 (UTC)[reply]

Well, we know the trajectory quite precisely, but the problem is that the Trans-Neptunian objects aren't comprehensively mapped out, and there may be large objects Voyager will encounter. Now the chances of an impact are extremely small, but even the most modest of gravitational deflection could have a major effect on the location, over centuries. So, the time period elapsed would be important in knowing how great the error will be, and we also don't know how sophisticated our scanning devices will be by then. There's also the political climate to consider in the future. That is, would they really think retrieving Voyager was a good use of taxpayer money ? So yes, unfortunately, this does get into crystal ball category. StuRat (talk) 19:08, 30 October 2017 (UTC)[reply]

The two Voyager missions will start the process of shutting down according to the schedule here. According to that webpage (from NASA) in 2020-2021, NASA will begin powering down various science experiments on the probes to conserve fuel, and all science experiments will cease by 2025, however NASA will still receive telemetry data from the probes until about 2036, when all power to the probes will fail completely. --Jayron32 19:19, 30 October 2017 (UTC)[reply]

Also, you mentioned manned space travel, but such a task would be far better suited to a unmanned spacecraft. That is, unless we develop some way to get there much faster, such a mission would take years, and a human would need food, water, air, heat, etc., for all that time. (Considering that they've been flying away from Earth for over 40 years now, even if we had some way to get there 10 times as fast, that would be 4 years, and by then they would have moved on a bit further, and then we have to add the time to locate and retrieve the ship, and the return trip, so we'd be talking about some 9 years.) StuRat (talk) 19:31, 30 October 2017 (UTC)[reply]

There was an XKCD "Whatif" column about retrieving Voyager. [14] Unfortunately, it's one of the early ones that's not really referenced. But you can usually trust Randall Munroe's math. ApLundell (talk) 20:29, 30 October 2017 (UTC)[reply]

Excellent info. But what if a chemical rocket with planetary gravity assists was used to get part of the way there, with fast acceleration, then ejected, using an ion engine for the rest ? Hopefully that combo would cut the time down somewhat. StuRat (talk) 21:06, 30 October 2017 (UTC)[reply]

If we don't have to wait until it goes dark then I think two missions would be most realistic. Mission one catches up to Voyager 1 when it's still transmitting, grabs hold of it, and brings enough reliable resources to keep transmitting for far longer. Mission two launches when rocket technology is good enough for a return mission. PrimeHunter (talk) 21:14, 30 October 2017 (UTC)[reply]

This is no "crystal balling" but plain madness! Are you aware of the pricetags of such projects? In case you are a multi-billionair dump you money where you like, else get sober and think again about asking this. --Kharon (talk) 02:07, 31 October 2017 (UTC)[reply]

Actually cost may be less of a factor than you would think, if the cost of space travel starts to steadily decrease. Give it a century, and such a thing might be financially feasible. In particular, at some point I would expect space probes to start being mass produced, and no longer cost billions each. StuRat (talk) 04:20, 31 October 2017 (UTC)[reply]

Even so, such an exercise would be pretty pointless. I'm struggling to think of anything that could be usefully gained from physically studying Voyager 1.--Shantavira|^{feed me} 07:55, 31 October 2017 (UTC)[reply]

The effects on technology of long-time exposure to interstellar space? If the return cost becomes low enough then you might want that before launching more expensive interstellar missions, but it would probably be easier to extrapolate from short-term exposure. Future space historians may also be interested. It would be a nice museum exhibition. PrimeHunter (talk) 10:59, 31 October 2017 (UTC)[reply]

October 31

A question on the math desk about math in med school raised this question in my mind: What types of math are used in (a) astronomy, (b) physics, (c) chemistry, (d) biology, and (e) geology? (I presume that for physics the answer is “all of it except number theory”, so I’m more interested in the answers for the others.) Loraof (talk) 00:53, 31 October 2017 (UTC)[reply]

Stoichiometry and Statistics are special tools of choice in chemistry and biology. In Astronomy Geometry (yes that counts as math) has wide application but then the "included" Astrophysics is physics (and chemistry) too! Like in Astronomy physic science is used as base in every "natural" science, so what applies to physics applies to all the others you mentioned at some point. --Kharon (talk) 01:50, 31 October 2017 (UTC)[reply]

Some of the nastier math in biology is encountered in the context of Ronald Fisher regarding population genetics. But some serious computational issues go into things like protein structure prediction. Of course this is not an exhaustive list. Wnt (talk) 02:18, 31 October 2017 (UTC)[reply]

It depends on which specific subfield you are working in; for many fields of Chemistry, daily working knowledge of mathematics beyond basic algebra probably isn't necessary, though for some others being able to understand, calculus is essential, such as the fourier transform or partial differential equations involved in Lagrangian mechanics and Hamiltonian mechanics, especially in people who work in physical chemistry. --Jayron32 10:48, 31 October 2017 (UTC)[reply]