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December 3

Do facial toning exercises work?

Do facial toning exercises work? I don't see how face muscles could be different from other muscles and not adapt when stimulated by physical exercise, but it could all be just snake oil. Or the effect could be minimal.

The facial toning article might need some quality peer-reviewed scientific sources. Most of it are alternative medicine, Chinese medicine, providers of services and so on. --Hofhof (talk) 00:48, 3 December 2017 (UTC)[reply]

I agree the article is problematic, so I mentioned it at Wikipedia:Fringe theories/Noticeboard yesterday. It looks like someone has already significant cut down on the poorly sourced content. Nil Einne (talk) 12:02, 4 December 2017 (UTC)[reply]

Fire nozzles

How do different fire nozzles (fog nozzle, straight-tip nozzle, solid-bore nozzle, etc.) differ in terms of their internal profile? I.e. how do they create the required pattern? 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 10:00, 3 December 2017 (UTC)[reply]

Sounds like a homework question. Have you tried googling it? Aspro (talk) 15:44, 3 December 2017 (UTC)[reply]

In principle like the exchangeable tips for Pastry bags. --Kharon (talk) 22:01, 3 December 2017 (UTC)[reply]

No, this is NOT a homework question -- unless you count a writer's book research as homework! 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 02:57, 4 December 2017 (UTC)[reply]

A large number of U.S. patents have been issued for various fire hose nozzles: you can find images and diagrams - including cross-sections and detailed explanations - by reviewing those. The official web site of the USPTO search engine lets you search by title; you may find Google's patent-search engine interface easier to browse for images. Many of the patents are over a century old, (and probably expired); and you can probably use the imagery from any of these patent filings at no cost.

Bear in mind that not all patents-granted are for devices that actually work!

Nimur (talk) 03:14, 4 December 2017 (UTC)[reply]

Thanks, I'll try that -- in the meantime, anyone else who has this info is welcome to share! 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 03:16, 4 December 2017 (UTC)[reply]

I suppose you could look at Spray nozzle for a start... --jpgordon^{𝄢𝄆 𝄐𝄇} 05:15, 4 December 2017 (UTC)[reply]

If the patent office examiner concludes that a device built according to the specification will not do what it claims he will not accept the application. This is only fair to others who may be working on similar lines. The patent will cite the "prior art", i.e. previous inventions which are improved upon. Of course, there's no requirement to exploit the patent once granted, but if it's not worked there's a risk of losing protection (which is only for a maximum of twenty years anyway). 92.8.221.62 (talk) 17:09, 6 December 2017 (UTC)[reply]

92.8 is substantively correct here, according to patentability, a device must be 1) eligible 2) novel (does not yet exist) 3) non-obvious and 4) useful. #4 is the relevent bit here; a device which cannot work as intended fails the usefulness criteria. That is why patent offices will generall reject any application for a perpetual motion machine, which cannot perform their intended function, and thus fail the usefulness criteria. --Jayron 32 17:47, 6 December 2017 (UTC)[reply]

Construction of Britain’s railways in the 1800s

Who built Britain’s railways back in the 1800s? Did private construction companies exist back then? Who did people like Brunel work for? 90.192.100.85 (talk) 19:00, 3 December 2017 (UTC)[reply]

See History of rail transport in Great Britain - mostly small private companies applied for Acts of Parliament which allowed them to build lines between named towns. There was then a gradual process of amalgamation, leading to a small number of large companies.Wymspen (talk) 19:08, 3 December 2017 (UTC)[reply]

But did those small companies hire construction companies to build it for them? And did they hire people like Brunel? 90.192.100.85 (talk) 22:10, 3 December 2017 (UTC)[reply]

Note that there's also a distinct split between railway companies (who are mostly speculative fund raisers during this phase), chief engineers, and then contractors. The chief engineer (Stephenson, Brunel, Locke) would be engaged by the railway company to plan the route, and to decide the important trade-offs between the quality of the finished line (its level and ease of operation) vs. the construction costs and the land purchase costs. A famous engineer might have several such projects on the go at once. They might design a major engineering work such as a bridge, or they might leave it to others. The actual building work would then be done by a contractor, such as Morton Peto, Thomas Brassey, Rowland Brotherhood or Thomas A. Walker. Andy Dingley (talk) 22:18, 3 December 2017 (UTC)[reply]

I see. So would the modern equivalents be cheif engineer = consultancy, railway company = client/infrastructure authority, contractor = construction contractor? 82.132.216.104 (talk) 17:53, 4 December 2017 (UTC)[reply]

Some very good books on Brunel are Stephen K Jones' 3 volume set Brunel in South Wales ISBN 9780752432366. Much of the general history of Brunel is coloured by Tom Rolt's old paperback biography of him, which over-emphasises Bristol and especially the suspension bridge, whilst ignoring the more voluminous work in Wales - and all Brunel's standard gauge work for the Taff Vale Railway. Andy Dingley (talk) 22:26, 3 December 2017 (UTC)[reply]

Another book worth a read is, Webster, Norman W. (1972). Britain's First Trunk Line – the Grand Junction Railway. Bath: Adams & Dart. ISBN 0-239-00105-2. {{cite book}}: Invalid |ref=harv (help) which is a history of the construction of the Grand Junction Railway, later the core of the LNWR, and the book covers the process of designing and constructing such a railway very well.Andy Dingley (talk) 12:34, 4 December 2017 (UTC)[reply]

John Brogden and Sons was a very early builder of railways in the UK, but the company failed after Brogden's death when his sons seem to have mismanaged it. The company is of interest to me because it was instrumental in building the first railway lines in New Zealand, even though it was under controversial circumstances. One of my ancestors emigrated to NZ in 1872, apparently as a Brogden employee. If anyone can shed light on employment contracts or employee lists or other circumstances, I'd be interested to hear. Akld guy (talk) 23:42, 3 December 2017 (UTC)[reply]

So most were specialist railway contractors? These days railways just seem to be built by general construction companies. 90.192.100.85 (talk) 18:03, 4 December 2017 (UTC)[reply]

Possibly because the construction of a new railway is a comparatively rare event these days and companies need to keep their expensive plant occupied. Alansplodge (talk) 15:51, 5 December 2017 (UTC)[reply]

Yes, there was railway mania at that time. A group would form a company to build a railway, issue a prospectus, and there would be heavy demand for the shares. These days not much railway building goes on, although in the past few days the government has signalled that it would like to reopen the lines which were closed in the sixties. The Channel tunnel rail link was built by a dedicated company and an alternative is joint participation - see East West Rail Link. 92.8.223.3 (talk) 18:11, 5 December 2017 (UTC)[reply]

Most of the railways (by size and length) were built after the mania period. Andy Dingley (talk) 18:18, 5 December 2017 (UTC)[reply]

America did it a bit differently. They industrialized later, the population density was lower and country was bigger and from 1850 to 1871 railroads got free land if they gave gov't freight a discount to encourage such expensive national improvements. Perhaps not coincidentally, rail exploded in the 1850s. The continent's biggest river had a rail bridge by 1856 (into Iowa) and the state's newness, farmability, treelessness, featurelessness and square land plots caused a mania of parallel railways too close to each other. To this day Iowa has too many East-West lines of unusually small major settlements. Sagittarian Milky Way (talk) 00:56, 6 December 2017 (UTC)[reply]

The men who actually built the railways (and canals, before that) were known as navvies. Carbon Caryatid (talk) 00:53, 8 December 2017 (UTC)[reply]

Difference between natural gas and coal for global warming.

People seem to say all over that the natural gas is preferable to the coal and by using the gas the global warming will be delayed or even eliminated? I don't see any difference at all with the exception that the coal gives away soot. The soot should eventually settle on the ground especially in areas with frequent rain. Both coal and natural gas contribute to $CO_{2}$ growth in the atmosphere. What is the difference? AboutFace 22 (talk) 20:43, 3 December 2017 (UTC)[reply]

In general, if you remove all subsidies, direct (tax breaks/burdens) and indiret (use of public land without remediation to the environment, scrubbing of pollutants) then whichever fuel is cheaper will generally also be cleaner, since it will involve the least cost; i.e., the least effort and waste. Coal burning, for example, also produces oxides of sulfur. There is also the relative cost of extraction and transportation.

When you have sweatheart deals, government giveaways, and artificial burdens posed by regulations meant to favor one industry over another, such market calculations become skewed, and you are dealing with hidden costs. For example, natural gas means natural gas pipelines, which means fires, construction at public cost, and use of eminent domain; while use of coal can potentially mean strip mining, coal-mine fires, and higher air pollution.

Otherwise, CO2 is CO2. See Ol Doinyo Lengai, which produces ~6,000 tons of CO2 daily. μηδείς (talk) 21:15, 3 December 2017 (UTC)[reply]

One differences among fuels is that different chemicals lead to different amounts of carbon dioxide and water vapor to supply a certain amount of energy. See Natural gas#Carbon dioxide emissions for cited info. DMacks (talk) 21:23, 3 December 2017 (UTC)[reply]

Correct. With coal C+O2=CO2+ not very much heat. With nat gas CH4+2O2=CO2+2H2O plus about twice as much heat, the extra from the oxidation of the hydrogen. So for a given whiff of harmless CO2 you get twice as much heat with gas than coal, plus of course some deadly dihydrogen oxide. Greglocock (talk) 22:15, 3 December 2017 (UTC)[reply]

Coal also contains sulphur, the burning of which can lead to acid rain, another reason why you might prefer not to use it. [1] Alansplodge (talk) 23:41, 3 December 2017 (UTC)[reply]

Flue gas desulfurization is a well-known and widely-used technology -- and if you want to go even cleaner, coal gasification allows complete removal of sulfur (at extra cost). 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 03:02, 4 December 2017 (UTC)[reply]

Thanks for repeating this important fact, which I mentioned two days ago when I talked about scrubbing and oxides of sulfur. μηδείς (talk) 16:32, 4 December 2017 (UTC)[reply]

Thanks, the difference between coal and natural gas as an energy source is really what matters in the bottom line, I was using pure carbon equivalence as a proxy, but the same economic point holds--whatever form of energy is cheapest when all subsidies are removed and all costs factored in (including remediation, pollution, and disposal) will be the cleanest. In our case, at this point, it's nuclear. μηδείς (talk) 00:17, 4 December 2017 (UTC)[reply]

How do you propose factoring in the cost of carbon dioxide? Sagittarian Milky Way (talk) 01:53, 4 December 2017 (UTC)[reply]

Why should we? 2601:646:8E01:7E0B:9559:4F0F:AF97:BC2A (talk) 03:02, 4 December 2017 (UTC)[reply]

Well, SMW, if you are just comparing coal and natural gas, the CO2 cancels out as a factor if one assumes carbon equivalence, in which case methane at the destination (other costs ignored) is a cheaper source of heat, and the question has already been answered. If you assume CO2 is a pollutant that needs to be remediated, then the burden is on you to demonstrate this and its cost. Since I have already mentioned nuclear power, I don't see your ultimate point. μηδείς (talk) 16:32, 4 December 2017 (UTC)[reply]

I don't need to prove what all the climatology PhDs have figured out. Enough CO2 to significantly increase the greenhouse effect unless [magic] means more of it is a pollutant. Eh, here it is anyway. The drawback of nuclear power is that many people are stupid and think they cause lots of radiation in peoples' homes or they can explode with the power of Hiroshima, don't know that Chernobyl was less safe than American ones and would be against new ones being built near them even outside a seismic/tsunami zone. Even if that's a minority maybe politicians (who would have to approve permit) would rather not alienate any net voters. They also take very long to turn on after approval so the government could be different people with a different view before the plant can ever start reducing carbon and the plant gets shut down (i.e. Shoreham Nuclear Power Plant took 11 years and 6 billion dollars to build and was turned off forever during 5% power tests). So though it might be best in principle in the real world it might take a dictator. Maybe in the industrializing democracies the populace wouldn't care though, they'd rather have jobs and cheap electricity and the risk of meltdown doesn't seem as significant when many people die of things development could prevent every day (i.e. tropical diseases). Sagittarian Milky Way (talk) 19:31, 4 December 2017 (UTC)[reply]

Um, no, SMW, the burden of proof lies on the one making the claim. If you want to cite the IPCC as proof, well they are a politically appointed board who don't do any science at all (it's in the lead of their article and in their mission statement) and who by their very name start with Climate Change as their premise, not objectivity. I am making no claim as to whether man-released CO2 is a problem or not. If it is, then the cost of remediating it should be included, which I mentioned in my first post. Your insistence that I recognize your concern is moral hysteria, not reasoned discourse. μηδείς (talk) 02:29, 6 December 2017 (UTC)[reply]

Not to mention that the IPCC is organized and funded by the UN -- which means that, like the UN, they are influenced by third-world interests (so they have a vested interest in hindering industrial growth in civilized nations so that third-world nations could get ahead). 2601:646:8E01:7E0B:F9B4:9A86:7938:FC5D (talk) 05:24, 6 December 2017 (UTC)[reply]

Then couldn't I say you're making the claim "there's a realistic possibility that man-released CO2 is not a problem"? This seems like a tie then. Then I defer to the experts in the field who are both very smart and the best we've got (humans having no access to superhuman truth sources) and before even reading their papers it seems more likely that the scientists are right. And since vials of CO2 get hotter in the sun then identical vials of air, even if no research was done on climate whatsoever (hint: false) it'd be simpler and more likely (Occam's Razor) for the scientists to be right then for something to prevent that which you're sure probably exists even though you don't what. Now counterintuitive findings are not unheard of in science and to actually be science and get anywhere close to proof (you know there's no absolute proof in science) you have do the math and try to rule these out but luckily for us thousands of scientists did the math and it turns out no matter how rigorously they go (i.e. cement setting, contrail water, airplane vs. low altitude emissions and urban heat island) the salvatory homeostasic effect never happens (and I bet the very few contrarians are irrationally optimistic or bribed) Seems like you're the one with more burden of evidence. Tell me by what evidence is the greenhouse effect not working in the atmosphere the obvious way more likely. And how thousands of scientists' atmosphere calculations are wrong. Whatever evidence you have I'd love to see it. Evidence for such a popular and old-news scientific topic is so easy to find, if you're too lazy or skeptical to Google such common knowledge but still manage to have such extreme agnosticism, skepticism or whatever on the topic that's not my problem. (and I know you're not lazy or you'd be a Democrat) Since you so insist I googled "evidence for anthropogenic global warming" and the first result was https://climate.nasa.gov/evidence/ NASA] (NASA isn't bribed by a vast conspiracy right?) which has links to numerous scientific society statements (all bribed?), the doesn't do any science (strawman) IPCC, B.D. Santer et.al., “A search for human influences on the thermal structure of the atmosphere,” Nature vol 382, 4 July 1996, 39-46, Gabriele C. Hegerl, “Detecting Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method,” Journal of Climate, v. 9, October 1996, 2281-2306, V. Ramaswamy et.al., “Anthropogenic and Natural Influences in the Evolution of Lower Stratospheric Cooling,” Science 311 (24 February 2006), 1138-1141, B.D. Santer et.al. and “Contributions of Anthropogenic and Natural Forcing to Recent Tropopause Height Changes,” Science vol. 301 (25 July 2003), 479-483.

I also found this from the UK government. It says "Climate change presents a unique challenge for economics: it is the greatest example of market failure we have ever seen.". The British government can't be bribed too right? (by who? the solar companies? they're not rich). And about the UN, most of the budget is paid by rich countries: [2]. Do you have evidence the General Assembly has more influence on it than their budget sources? At any rate, gaining slightly if rich countries cut sooner (or, less insignificantly, free nuclear plants or windmills to the third world) doesn't mean their answer can't still be right. So I guess my answer then is yes you would be okay with that cost being included (consistent! great!) but you're not sure if it exists. What you agree with on sulfur is called internalizing a negative externality which is actually very similar to evil living wage and socialized medicine laws where the costs of paying employees less than needed to live is passed to the employer instead of evil Food Stamps, Medicaid, small town public transit so shitty the last bus is 5-something, taxes for the fraction of welfare office employee wages that wouldn't be needed if full-time workers didn't need welfare and other otherwise cuttable welfares. And the communist healthcare where the cost of people who take their chances without insurance but then cry to the hospital to fix their broken leg so the public pays out of mercy is then passed on to those irresponsible people (poorly implemented in America I know but the general idea's good) Consistency is good! I get that Soviet-bloc life was terrible/communism won't work/the Democratic approach on crime sucks balls but just because liberals believe something doesn't make it automatically bullshit. (the cost of switching from fossil fuels over a few decades isn't even that big. Plus the new sources will last longer than a few hundred yea Sagittarian Milky Way (talk) 07:02, 6 December 2017 (UTC)[reply]

The planet is doomed anyway and it is scary. AboutFace 22 (talk) 22:29, 3 December 2017 (UTC)[reply]

If you have three and a half minutes, here's a video on the Natural Gas Initiative from my old professor, Mark Zoback. He explains his view on why natural gas is part of the bigger picture for energy policy in the United States and the rest of the world.

Optimism is irrelevant - and for that matter, so is pessimism. Actual engineers and scientists are going to work on these problems, whether the solutions are easy or hard.

Nimur (talk) 03:23, 4 December 2017 (UTC)[reply]

The earth is not doomed, at least not anytime soon. We might be doomed, but the earth is not. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:03, 4 December 2017 (UTC)[reply]

I'm a little surprised that the above answers aren't clearer. The difference between coal and natural gas is how much CO2 is produced per unit of usable energy, a concept known as the emission intensity. A 2011 IPCC review indicated that per kilowatt-hour of electricity generated burning typical coal released 1000 grams of CO2. For comparison, you only get about 470 grams of CO2 if you burn natural gas to generate a kilowatt-hour of electricity. So, for the same amount of energy, natural gas releases only about half as much CO2. The difference arises from the fact that when you burn natural gas (e.g. CH4) you get energy by converting both the C to CO2 and the H to H2O, whereas almost all the energy in coal comes from burning carbon. See also life-cycle greenhouse-gas emissions of energy sources. Dragons flight (talk) 13:42, 4 December 2017 (UTC)[reply]

^^^ That's the correct answer, but I should add that methane released from leaky natural gas infrastructure does have a stronger short-term effect on global warming... and I would speculate we're building a lot of brand new natural gas infrastructure that eventually will be old leaky natural gas infrastructure... Wnt (talk) 15:41, 4 December 2017 (UTC)[reply]

December 4

Color and pattern convergence across unrelated species

Today I saw a Hermit Thrush and was struck by how much it looked like a Spotted Sandpiper, with its brown back and white spotted belly. The birds are not closely related and they live in different habitats, so why are their patterns so similar? I have also observed that some tropical fish have patterns similar to warblers. Why would a bird and fish have the same face pattern? Is it just a coincidence, or does the resemblance have to do with some pigmentation process shared across all vertebrates? 169.228.159.244 (talk) 05:12, 4 December 2017 (UTC)[reply]

See Convergent evolution. ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:01, 4 December 2017 (UTC)[reply]

That's not really much of an answer -- one lives in coniferous forest, the other near fresh water. They both do nest on the ground, which presumably has something to do with it (they should blend in with a nest from a distance, which puts limits on the dorsal plumage). But overall, I would be lying if I tried to say if the similarity was coincidence or adaptive or if so then as an adaptation to what. Wnt (talk) 15:37, 4 December 2017 (UTC)[reply]

It's a good partial answer: mottling is good at obscuring a figure both for many types of viewers and against many backgrounds. Consider that many fish and birds both benefit from light undersides and dark top sides, and for the same reason, even though their habitats are very different.

But there's another angle too: lots of animal patterns are created by reaction diffusion systems, as described by The_Chemical_Basis_of_Morphogenesis (well ok he was guessing, but later work has confirmed this is the case in many specific examples). So there is also likely an aspect of a shared basis of pattern formation, shared even by birds and fish. Pattern_formation#Biology is sparse, but Animal_coloration#Mechanisms_of_colour_production_in_animals has plenty of good reading, links, and refs. SemanticMantis (talk) 18:21, 4 December 2017 (UTC)[reply]

And to clarify: I think the two birds in the fist example are well explained by a combination of convergent evolution, general effectiveness of mottling, and similar mechanistic basis of coat patterns. For the fish and the bird, I don't think an appeal to convergent evolution is very apt. In that case, sexual selection is likely a strong force influencing the showy pattern on the bird and fish. There may be some mechanisms of pigmentation and patterning shared between the bird and fish that makes these sorts of patterns more likely to occur, but that is just a conceptual possibility, not a claim I would make. There is a lot of research about what pigment/pattern features are common to all vertebrates, as well as the genetic basis of such. See here [3] [4] [5] for a selection of scholarly overviews. These are behind academic paywalls, I can provide copies to anyone who is interested. The first paper linked is especially relevant, using both a bird and a fish as model species in the study of pattern formation. SemanticMantis (talk) 19:12, 4 December 2017 (UTC)[reply]

This is a great answer, and I don't want to disparage it in the least. But ... I abandoned starting down a similar road in my own because I couldn't see how to get to numbers and say coincidence or not. There is no shortage of beautiful birds with spectacular plumage that can't be confused for anything else. Yet most birds look, well, kind of plain, at least for birds. If there's a mechanism that enforces plainness, then does a near match in appearance result from a random walk within a narrow set of rules that some species diverged from during evolution, or does it mean that it is a convergent set of adaptations? I'm not sure there is a difference between those two things... Wnt (talk) 23:34, 4 December 2017 (UTC)[reply]

In my circles, people get touchy about whether or not a given trait can/should be considered "adaptive", especially in the narrow sense of providing a clear fitness advantage. In that light, your two options are indeed rather different, as the one case is "this is the way it has worked, and it doesn't hinder", whereas the other is "offspring with this trait have more reproductive success than those without". My WP:OR is that truly neutral traits are vanishingly rare, much like pulling zero at random out of the (-1,1) interval has probability zero. SemanticMantis (talk) 17:13, 5 December 2017 (UTC)[reply]

As for birds, note that brown coloration with speckling is very widespread, and may even be a symplesiomorphy or 'common primitive trait' of the birds, especially given that it is found in many chicks (consider the speckles of ducklings, so the pattern may also be an example of neoteny. In other words, this is an old pattern still found in the young of many species, as well as even ratites like the Hooded Tinamou (right) which are more closely related to the Ostrich (speckled chick (left) than to thrushes or snipes.

A similar phenomenon occurs in mammals, with the brown/black -- tan/red -- white tricolor agouti pattern found in many dogs (collies, beagles, German shepherds), calico-cats, horses, and guinea pigs with a dominant color highlighted, often on the head and limbs with patches of the other colors.

All of this points to the common genetic pathways alluded to above. We should also explicitly mention counter shading, as I dont' think it's been linked to above. μηδείς (talk) 18:12, 5 December 2017 (UTC)[reply]

Another relevant article, not yet linked: Piebald (and related links in 'See also' section). 2606:A000:4C0C:E200:7851:71F8:C463:FC20 (talk) 23:54, 5 December 2017 (UTC)[reply]

Thank you all, interesting links! The camo explanation makes sense for why the thrush and sandpiper look similar. 169.228.150.149 (talk) 23:57, 5 December 2017 (UTC)[reply]

What's this arachnoid?

[6][7]

Sorry for the quality but you can still see its very thin legs. Sagittarian Milky Way (talk) 12:39, 4 December 2017 (UTC)[reply]

Hard to tell because the picture is fuzzy, but it could be a pholcus phalangioides (cellar spider), which are common worldwide and have long legs similar to your picture. --Jayron 32 13:21, 4 December 2017 (UTC)[reply]

It does look like that, probably is. Almost certainly a member of the Pholcidae. SemanticMantis (talk) 18:14, 4 December 2017 (UTC)[reply]

Thanks both. I'd seen this distinctive but ugly spider body plan (are there any pretty ones?) more than once and wondered what it was. Sagittarian Milky Way (talk) 18:37, 4 December 2017 (UTC)[reply]

Beauty is in the eye of the beholder. --Jayron 32 18:47, 4 December 2017 (UTC)[reply]

There are many lovely spiders. E.g. the peacock spider has many fans, even among non-spider-lovers. Spiders often pop up over at /r/awwnverts, Reddit's clearinghouse for photos of cute invertebrates. SemanticMantis (talk) 19:22, 4 December 2017 (UTC)[reply]

Spiders make me want to put shoe in hand. The peacock's.. a mixture of pretty and repulsive. Now insects I generally don't mind as long as they stay pets, not pests. Sagittarian Milky Way (talk) 19:43, 4 December 2017 (UTC)[reply]

Modifying magnetic pendulum circuit for larger pendulum swings

I want to make a pendulum swing back and forth using the power from a battery. I bought a solar-powered dancing flower thing and disassembled it to get this stuff which generates a regular magnetic pulse. The problem is that the swings are quite small. To get larger swings do I need a stronger magnetic pulse or just one with longer timing? Also, what is that coil called (so I can search AliExpress for a bigger one if needed)? Thanks.

It doesn't generate a regular pulse, it senses the pendulum approaching and then generates the pulse in response. The timing is from the mechanical behaviour of the pendulum

2\pi {\sqrt {l/g}}

. A bit more complicated for a flower linkage, and some of them do generate timed pulses.

If you increase the current through the coil, you can increase the power and the possible mass of the pendulum, or the extent of the swing. You can do this with a single transistor amplifier, but (IMHE) those flowers are so tiny and their coils wound with such thin wire that this itself is difficult.

I'd suggest starting again from scratch. It's a simple circuit, it's not hard to make. There should be circuits for it on the web. You can wind the coil yourself quite easily. Some of these sold as kits use a PCB board with a flat coil etched onto them. Those are (again IMHE) too weak, as they have too few turns. Andy Dingley (talk) 15:00, 4 December 2017 (UTC)[reply]

http://www.trainelectronics.com/Pendulum/article.htm Andy Dingley (talk) 15:03, 4 December 2017 (UTC)[reply]

Winding

Why does being winded or blunt trauma to the stomach often result in nausea straight after? I don’t mean shock which may set in later if severe enough. I mean nausea which is often immediate and goes away quickly. Is it just to do with the muscles in that area going into spasm? 82.132.216.104 (talk) 20:40, 4 December 2017 (UTC)[reply]

Our article Celiac plexus#Clinical significance gives a brief explanation. Dbfirs 21:49, 4 December 2017 (UTC)[reply]

This article from the BBC [8] gives some additional information, as does this first aid website [9]. For a more scholarly reference, see this [10] journal article that discusses what happens when people "have the wind knocked out of them" SemanticMantis (talk) 17:09, 5 December 2017 (UTC)[reply]

Wikipedia does not give medical advice. Baseball Bugs (talk • contribs) 22:22, 4 December 2017 (UTC)[reply]

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The following is off topic, and has been swept under the hat. μηδείς (talk) 02:44, 5 December 2017 (UTC)[reply]

Which is a good thing to keep in mind, in case anyone should ask for it. --Trovatore (talk) 22:56, 4 December 2017 (UTC)[reply]

Don't fool around with others' edits. You can't even spell "medical". ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:00, 4 December 2017 (UTC)[reply]

That seems to have been Sluzzelin's typo, but I do seem to have messed up the hatting somehow. It wouldn't have been necessary if you hadn't dumped unusual HTML into the page. I'll see if I can fix the hatting. --Trovatore (talk) 23:10, 4 December 2017 (UTC)[reply]

Take your complaint to whoever wrote the disclaimer originally. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:14, 4 December 2017 (UTC)[reply]

Yes, Trovatore, the typo/slip was mine entirely, corrected 3 minutes later (before anyone else had posted). Whatever typos linger on, may have been originated by me, but I did not post them. ---Sluzzelin talk 23:28, 4 December 2017 (UTC)[reply]

Fair enough. I made my edit based on your earlier version, I guess. I moved the comment out of the center so I could respond to it. There was an edit conflict, which I examined and resolved in favor of my text, which propagated your original version. --Trovatore (talk) 23:30, 4 December 2017 (UTC)[reply]

Alright, well I corrected the propagated typo now. ---Sluzzelin talk 23:31, 4 December 2017 (UTC)[reply]

December 5

"Elastic collisions" and time travel

Can the theory of elastic collisions, extended into spacetime, still work when one of the colliding masses' velocities is timelike? IIRC, a character in HG Wells' The Time Machine raises the concern that a time traveller might be killed by arriving inside a solid object. (I'd assume that while traveling at full temporal speed, her density would be effectively reduced, and thus she'd be able to pass through solid matter without inflicting or sustaining significant damage, just as neutrinos can.) I'm wondering whether this could be avoided by colliding elastically with that other object, forcing it to time-travel out of the way in the same temporal direction. Neon Merlin 04:03, 5 December 2017 (UTC)[reply]

Whatever about about it being an elastic collision I think something like What If - Relativistic Baseball might happen. Dmcq (talk) 12:41, 5 December 2017 (UTC)[reply]

No, because one cannot move backwards in the time dimension. One of the things about Minkowski spacetime is that the time dimension only allows macroscopic objects to move in one direction according to the Arrow of time. Backwards time travel, except under highly restricted conditions (see T-symmetry) does not really happen without violating Causality. All sorts of Temporal paradoxes are introduced, both in terms of basic lay explanations (like the Grandfather paradox), and mathematically rigorous explanations (see Causal structure). Simply put, the timelike dimension does not obey the same rules as the three spacelike dimensions, and cannot be treated as such. It is true that the mathematics is arbitrary as regards to which direction time flows; but basically once you have aligned your arrow of time to designate a future and a past (time orientability), spacetime only moves in one direction if multiple observers all agree on the direction time is moving; i.e. once the universe gets going one way, it all goes that way. --Jayron 32 12:55, 5 December 2017 (UTC)[reply]

In order to dispute the Arrow of time, space has to be counted as something that in some way can be dissipated. Before it might be yes as well as no. But the OP seem to be assuming some kind of Doppler effect as applied to teleportation. --Askedonty (talk) 16:47, 5 December 2017 (UTC)[reply]

Just a side note here — I am not sure that word timelike means what you think it means. A normal (bradyonic) particle's four-momentum is always timelike; the weird case would be spacelike. I can't seem to work out in my head right now just what "four-velocity" ought to be, but I think, if there is such a thing, it would normally be timelike. --Trovatore (talk) 23:32, 5 December 2017 (UTC)[reply]

Ah, four-velocity; if it'd been a snake it'd'a bit me. --Trovatore (talk) 23:45, 5 December 2017 (UTC)[reply]

Yeah, but after you de-Lorentz-transmogrify it - which you would have to do during any analysis that adds or subtracts vectors - you still get the right answer, and unsurprisingly, the constant "c" drops out exactly as you would expect. One cannot defeat conservation of momentum nor conservation of energy, which are ultimately the only laws of interest when we study collisions under relativistic conditions!

Landau & Lifschitz Mechanics Chapter IV, §16; from whence, those who care to follow, we can derive relativistically-corrected Thomson scattering, and then further, Compton scattering ...

What we have in this question is a fun use of the English language to obfuscate the actual physics - which is much simpler than our OP wants to admit. Even when we consider motion in time- and space- - irrespective of how we write out our vectors - we cannot forget to conserve energy and momentum. These simple facts are what keeps our physics, and our conclusions, grounded in reality. After all, we are all "traveling in time," and always at "velocity" "ct/ct"! We need neither fictional machinery nor new physics to describe it!

At this time, I would remind our new initiates (e.g. our OP, User:NeonMerlin) that relativistically-correct scattering theory is hard physics - it takes several years of gruelling preparation to attain anything close to a complete understanding; but after you put in all the effort and solve a few thousand sample problems, let me assure you that you will never forget your efforts!

Nimur (talk) 19:33, 7 December 2017 (UTC)[reply]

Cconceptually, I suspect there are some scenarios within an extremely large gravitational field where the same object can appear arbitrarily close yet separated by long light cones and therefore time. The Einstein Cross is in essence, the same object at different points in time affecting telescopes on earth. It's not time travel per se but an interesting phenomena. Everyones current frame is at the tip of the time arrow and and we are constantly being held by the past. --DHeyward (talk) 00:10, 6 December 2017 (UTC)[reply]

Speed of molecular machines

I've seen this video and others of molecular machines. Is the speed shown the speed at which they operate, or are they faster or slower? Bubba73 ^{You talkin' to me?} 04:47, 5 December 2017 (UTC)[reply]

The animation is pretty famous - it's an excerpt from a 2003 work called Molecular Movies by Drew Berry, whose various animations have been published, and cited, in many peer-reviewed publications including Science. The original video has detailed narration and scientific commentary.

"The dynamics and molecular shapes were based on X-ray crystallographic models and other published scientific data sets. Leading scientists, including many Nobel Laureates, critiqued the animations during their development. Particular effort was made to ensure the relative shapes, sizes and 'real-time' dynamics were as accurate as possible."

And, in this 2012 TED talk, Berry again discusses the accuracy of the animations.

Of course, the real molecules "look" nothing like this - the molecule-scale features are too small to resolve with visible light!

After all, it's just a cartoon - but it is meant to be a realistic model, and effort was put toward that end.

Nimur (talk) 05:30, 5 December 2017 (UTC)[reply]

Thanks, that is fascinating stuff. Bubba73 ^{You talkin' to me?} 18:51, 5 December 2017 (UTC)[reply]

Resolved

If you look at 1:20 into that video [11], it describes a helicase spinning at the speed of a jet engine. Now a jet engine spins at tens of thousands of RPMs [12] so at least in this case a molecular machine is depicted as moving much slower than it actually does. --Bob K31416 (talk) 19:03, 5 December 2017 (UTC)[reply]

Why do people use that "resolved" tag? Don't they know it's like waving a red flag in front of a bull would be, if bulls could see red? More about the helicase here; looks like it has useful links to further reading. The max speed is 10,000 rpm.

I should point out more generally though that molecular machines work differently than the ones we know. ATP doesn't magically jump into a binding site for a helicase to turn, for example; it will jam in this way and that, fly away, another ATP comes, that flies away, between, countless water molecules, the occasional ADP or chloride ion tries ... who knows how long until a fit is made? Which brings us to the point that these are small distances, yet according to the Boltzmann distribution the molecules are moving faster than macroscopic objects. So they are doing an unfathomable amount of stuff that isn't shown in the video between every two frames that have a result you expect. That's why the ATP requirement at all - without it, that helicase would spin 10,000 rpm backward just as often as forward. That's another thing to notice -- in the microscopic world, there's practically no momentum built up by a spinning helicase compared to, say, a jet engine. The distances are small, after all - if something is say 100 angstroms in circumference, 10,000 rpm means it moves a tenth of a millimeter every minute. By contrast, the electrons in atoms that make up that engine may be moving around their nuclei at something like 1/137 the speed of light (this should be discussed at fine structure constant). Wnt (talk) 21:51, 5 December 2017 (UTC)[reply]

How are these videos made - do they calculate what the molecules will do or are they an animation of observations? Bubba73 ^{You talkin' to me?} 03:30, 6 December 2017 (UTC)[reply]

These specific animations are “cartoons” or pictures drawn by an artist, guided by actual scientific data like x-ray crystallography (which produces graphical results that require scientific training and discipline to interpret). In specific, the digital artist uses Maya and other specialized software. Molecule movements and trajectories can be programmed, like any other computer-aided animation - in a sense, this is Digital puppetry with atom-shaped puppets. The shapes and movements are meant to illustrate molecular motion, but they are not in themselves a “simulation” in the sense of computational chemistry or molecular dynamics scientific software. The author says in his presentation that it is “expressing science through art.”

Here’s another promotional video from the Linear Coherent Light Source team: using X-ray lasers to image nucleic acid reaction kinetics. That equipment, and the data it produces, are much newer but are in the same category as the type of pictures that Drew Berry would use to inform his animations. In the SLAC video, you can see a sort of transition from raw data to “science product” and finally to cartoon-for-layperson-consumption, as the narrator explains the science.

Nimur (talk) 18:43, 6 December 2017 (UTC)[reply]

Thank you. Bubba73 ^{You talkin' to me?} 00:34, 7 December 2017 (UTC)[reply]

Just here to note that Autodesk Maya has an article, so we can learn it's "specialized" as general purpose high quality animation rather than science-specialized. DMacks (talk) 06:32, 7 December 2017 (UTC)[reply]

Anthropology and VO2 max

I am looking for information regarding how VO2 max relates to ethnicity and how it has changed since early humans (possible relating to Endurance running hypothesis). On average do certain ethnicity have better VO2 max L/min? Trick on (talk) 18:01, 5 December 2017 (UTC)[reply]

Venlafaxine

One of the reported side effects of Venlafaxine is loss of appetite. By what mechanism does Venlafaxine exert this appetite suppressing effect? — Preceding unsigned comment added by 182.253.176.176 (talk) 19:51, 5 December 2017 (UTC)[reply]

Where did you see that reported side effect? ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:29, 5 December 2017 (UTC)[reply]

There's a comically long list at List of adverse effects of venlafaxine (are all these proved to a level of statistical significance?), which include weight loss, but not "loss of appetite" per se (and theoretically the two can be unlinked, as by uncoupling agents, though I doubt it here). It also gives nausea as a side effect; [13] adds constipation; so maybe that gives an explanation. But I don't know that. Since they are side effects I would be surprised to see detailed information about the mechanism but I haven't looked. Wnt (talk) 21:28, 5 December 2017 (UTC) ... Hmmm, having looked, at least the first four PubMed screens, not much obvious to me; [14] gives nausea as a side effect in meta-analysis but doesn't try (as I expected) to break down cause and effect. Found general support for antidepressants in binge eating disorder. [15] I could look harder if someone got me interested. Wnt (talk) 21:34, 5 December 2017 (UTC)[reply]

I just noticed the mixing of "adverse event" and "side effect" here to create "adverse effect." In our pharmacy school, students must know the difference between a Type A adverse event, Type B adverse event, side effect, and toxic effect. I understand that the general public doesn't need to know it, but mixing and matching words between "adverse event" and "side effect" in what claims to be an encyclopedia seems a bit clumsy to me. 209.149.113.5 (talk) 14:20, 6 December 2017 (UTC)[reply]

Since you don't have a talk page, I'll encourage here that you raise this issue at the appropriate article talk pages. I'll note that we have separate articles for adverse event and adverse effect, and at a glace they seem to be about (somewhat) distinct things. SemanticMantis (talk) 02:09, 7 December 2017 (UTC)[reply]

At least part of the cause it that venlafaxine is a serotonin reuptake inhibitor. This means it increases serotonin levels in the brain, and one of the effects of serotonin is to reduce appetite. The well-known anti-obesity drug fen-phen relies heavily on that mechanism. Looie496 (talk) 19:36, 6 December 2017 (UTC)[reply]

Yes, venlafaxine is an "upper," that is it acts as a psychostimulant for many people, improves attention span, reduces need for sleep, may cause insomnia. It is actually a dual serotonin and norepinephrine reuptake inhibitor. - AboutFace 22 (talk) 02:18, 7 December 2017 (UTC)[reply]

Ice-free northern Greenland

The Greenland article says The extreme north of Greenland, Peary Land, is not covered by an ice sheet, because the air there is too dry to produce snow, which is essential in the production and maintenance of an ice sheet. Why doesn't the main ice sheet spread over Peary Land? Is it unable to get past the fjord south of Peary Land (i.e. the ice that would go north just goes into the ocean instead), or is there some other reason? Nyttend (talk) 23:54, 5 December 2017 (UTC)[reply]

Didn't you just quote the answer to your own question? --Jayron 32 13:14, 6 December 2017 (UTC)[reply]

No. Nyttend backup (talk) 14:06, 6 December 2017 (UTC)[reply]

Question: "Why doesn't the main ice sheet spread over Peary Land?" Answer: "because the air there is too dry to produce snow, which is essential in the production and maintenance of an ice sheet". I am confused as to what you are asking if that is not the answer. If you can clarify your question in some meaningful way, then people can help you find the answer. --Jayron 32 14:47, 6 December 2017 (UTC)[reply]

I believe the question meant is "Why is the air so dry there that it cannot produce snow?" I do not know the answer to that, but there are, similarly, small areas of Antarctica without snow. Our article is at Antarctic oasis and it similarly fails to account for why these areas have the low humidity that causes lack of snowfall. Matt Deres (talk) 14:21, 6 December 2017 (UTC)[reply]

The question is: "Why doesn't the ice sheet to the south of Peary Land slide North and, eventually, cover Peary Land?" For background, ice sheets move. There are ice sheets moving into Peary Land. It is easy to find many photo collections of the ice sheet edge. They don't cover Peary Land because during the summer it warms too much. The ground is permafrost, which absorbs solar light. Also, ice in dry air will melt in direct sunlight even if the air is below freezing. (Just as you can see ice melting off a roof when it is well below freezing.) So, it is a flow and ebb system. The ice sheet moves in during the winter, but melts away during the summer. Overall, Peary Land is speckled with snow in the winter, but dry and clear in the summer. You can get information on this type of system easier by looking for information on arctic deserts in Alaska and Canada. 209.149.113.5 (talk) 17:47, 6 December 2017 (UTC)[reply]

Thank you for that explanation. It didn't occur to me that summer melting would be an issue; I figured that the sheer size of the sheet was great enough that melting wouldn't be able to prevent its expansion. And on sublimation, again I'd figured that only a small percentage would be lost, so thank you for correcting me. Nyttend (talk) 00:28, 7 December 2017 (UTC)[reply]

I thought the question clearly was about the ice moving, which you have also answered. It may also be mentioned that ice in dry air and sunlight may not only melt but may also sublime, i.e. evaporate directly from the solid state. --69.159.60.147 (talk) 19:46, 6 December 2017 (UTC)[reply]

It looks like the sheet did get in to Peary Land in the past. Here [16] is a scholarly article discussing the historical and current limits of that ice sheet, here [17] is another that includes more maps. SemanticMantis (talk) 19:42, 6 December 2017 (UTC)[reply]

December 7

Effect of CO2 emissions on the metabolic energy obtained from glucose

One of the basic biology factoids is that glycolysis + Kreb's cycle + oxidative phosphorylation gets "up to" 38 ATPs out of a glucose molecule.

It occurs to me that, just as the temperature of cooling water affects the efficiency of a power plant, the concentration of CO2 should affect the efficiency of respiration. Searching I found many articles on plants, but I wanted to look at the same from an animal point of view.

Back of the envelope calculation: carbon dioxide in Earth's atmosphere has gone from 280 to 407 ppm. Gibbs free energy includes a term for RT ln (407/280) = 8.134 J/K * 300 K * 0.374, which gets me 0.93 kJ per, I think, 1 mol of CO2 that crosses a membrane between these two concentrations. Since there are 6 CO2s per glucose, that gets 6.00 kJ of energy difference between the two conditions per starting glucose! If so, well, adenosine triphosphate cites a change in free energy of 3.4 kJ/mol, so that would be 1.64 fewer ATPs per starting glucose than in pre-industrial times. (Note this goes by ln, so it takes larger and larger increases in CO2 to reduce the ATP count further; a 1000000 ppm concentration would, by this calculation, reduce it by about ... 38 ATPs).

First, did I do something stupid in the calculation? I haven't used these chemical concepts this way before.

Next, is there a way to call shenanigans on it for external reasons? For example, the CO2 concentration in the lungs will be much higher on exhalation. However, I'm thinking that this might go up somehow in proportion to the air concentration ... actually, I have no idea one way or the other.

Could a decrease in ATP production tend to turn everyone into couch potatoes, make us feel like aerobic exercise is too hard, cause overeating and so on? Just woolgathering here. Wnt (talk) 02:34, 7 December 2017 (UTC)[reply]

This appears to say the first noticeable without equipment effects don't start till 1000 ppm. Sagittarian Milky Way (talk) 03:11, 7 December 2017 (UTC)[reply]

I think that type of value is determined by acute exposure rather than lifetime exposure. Also, note that it is possible to waste significant amounts of cellular energy (e.g. uncoupling agent) with relatively little perceived effect. Something like 2,4-Dinitrophenol could be marketed as a "dieting aid" (indicating substantial loss of energy), though it causes symptoms up to and including death at sufficient levels. If the math above is correct it describes less than a 5% reduction in energy from carbohydrates (less from fats because the H2O is not affected), which is scarcely noticeable for dieting purposes. Wnt (talk) 14:06, 7 December 2017 (UTC)[reply]

It'd be interesting to do an analysis of the rate of world record breaking in as many probably steroid-free less-team/people vs people (too many variables) outdoor aerobic sports as possible. I'm not sure if you could see a signal in the noise of numerous other factors i.e. once-a-generation+ x players causing more kids to want to be pro x players, and x players with sudden big improvements on the previous best are still appearing in major sports (like a man can be many inches too tall (Usain) and still pulverize 100m records, a man can shoot well while being bumped when no one else could (LeBron) and that huge Australian high school football player could possibly not be too slow to play NFL at that size. Are the outdoor more individual aerobic sports (i.e. marathoning) also still capable of having something like that happening in the near future screwing up trying to use their world record progression to see if something more than the usual slowdown of record-breaking is happening? If your math is correct it's probably been thought of by now and you'd probably hear about it at least as much as ocean acidification or runaway clathrates warming but it'd be nice to see research on someone kept at CO2s between 280 and 1000 for a long time. I now wonder if any important sports events had enough building-related CO2 or oxygen abnormality to affect the performances lol. Or if it'd be allowed to mess with the air of sports venues to increase your team's or event's performance or even favor the home team. Do the Denver Nuggets want to try installing airlocks and O2 injection during games? Does Tokyo want more world records in their games? Make them play in 40% O2 at 60% pressure! Sagittarian Milky Way (talk) 18:40, 7 December 2017 (UTC)[reply]

You problems are: (i) you do not take into account the limited efficiency of the Kreb's cycle. 38 ATPs contain much less energy than that is released during oxidation of 1 molecule of glucose. The remaining energy turns into heat. So, when you calculate balance of Gibbs (or free) energy you need to take this into account. (ii) In addition you seems to confuse Gibbs (or free) energy and energy itself. The free energy is only useful when you want to determine the direction of a reaction: will glucose oxidase or will it form instead!? On the other hand the true energy balance does not depend much on the external CO2 concentration. So, the Kreb's cycle consists of a fixed number of steps. Each step gives the fixed number of ATPs. This will not change as the CO2 concentration increases. The changes of the Gibbs energy that you refer to are essentially changes in entropy multiplied by temperature. Ruslik_Zero 20:47, 7 December 2017 (UTC)[reply]

@Ruslik0: The Krebs cycle involves a fixed amount of reduction and phosphorylation producing 10 NADH, 2 FADH2, and 4 ATP, it is true. But oxidative phosphorylation is less certain and is said to produce "up to" 34 ATP (3 per NADH and 2 per FADH2). There are costs in moving precursors and products (e.g. NADH, ATP) to keep them on hand to make the reaction go forward. Additionally, alternate mechanisms exist that generally have a lower yield. The result is that estimates tend to say things like "30 to 38 ATP", though it looks like eukaryotes can't hit the top figure.

Whenever there is a choice of regulated mechanisms, this means that the final energy figure has a chance to talk back to the reaction. For example, if ATP is produced abundantly in the mitochondrion I think it might be valuable to let it diffuse out through a channel, though I don't know that. But if anemic amounts are produced, a proton from the gradient might be spent wringing out ATPs from a less rich storehouse inside the organelle. Similarly, one of the alternate biochemical mechanisms might serve to add some extra free energy to the reaction to keep the process going. My memory of metabolism is limited, but it is surely not a rigid reaction that can be allowed to sputter to a halt based on a small change in free energy. Note that although a typical figure lists a metabolic efficiency under 40%, it is more like 50% in cells due to free energy considerations. [18] In other words, if ATP and ADP had exactly the same amount of energy in their chemical bonds, the cell has 10 times more ATP, so any reaction ATP + X -> ADP + Y would still be pushed forward, which means that that 10% of the energy was never actually lost to begin with. Now to be sure, yes, even if it is 50% I can say a 5% difference in ATP production is a 2.5% difference in efficiency, but it seems just as relevant no matter what I compare it to. Wnt (talk) 22:36, 7 December 2017 (UTC)[reply]

The Kerb's cycle efficiency can vary, of course, but it does not depend on the ambient CO2 partial pressure unless this pressure is extremely high. This is my point. Ruslik_Zero 20:26, 8 December 2017 (UTC)[reply]

Natural satellites of planets

I glanced through the Wikipedia material on the satellites (or moons) of planets. It gives very specific numbers, all of them in the order of one to a few dozens, for the known satellites of Jupiter, Saturn, Uranus and Neptune. But it also says that there's no agreed-upon threshold for size that objects have to pass so they can be considered satellites. And there doesn't seem to be any specification that a satellite mustn't be located in the planet's ring system. So why don't we say instead that these planets have billions and billions of satellites, all but a handful of which are tiny ones found in their ring systems? --Qnowledge (talk) 07:33, 7 December 2017 (UTC)[reply]

You are right to include the qualifier "natural". If you look at space debris you will see the term "satellite" is usually reserved for larger objects. 92.27.49.50 (talk) 11:06, 7 December 2017 (UTC)[reply]

Also, see Natural satellite#Definition of a moon. Dolphin (t) 12:54, 7 December 2017 (UTC)[reply]

I'm not sure, but I think some of that has to do with the Roche limit. A ring system like Saturn's contains particles that AFAIK would continue to break up under tidal forces were they not held together by chemical forces, i.e. electromagnetism rather than gravity. I think such assemblages are reasonably disqualified from being moons. (I'm not sure at the moment what distinguishes ring particles from shepherd moons, should look up later if someone doesn't explain) Wnt (talk) 14:11, 7 December 2017 (UTC) (withdrawn - see below)[reply]

Probably being big enough to be seen and have a significant shepherding effect. Ring particles in this solar system are only the size of a house or smaller. Since shepherd moons are big enough to be seen by spaceprobes the Roche limit isn't absolute and natural satellites big enough to be seen by them and thus named and numbered can have enough structural integrity to avoid being broken up by tidal forces. Sagittarian Milky Way (talk) 17:44, 7 December 2017 (UTC)[reply]

A Ring system can be regarded as one or sometimes even multiple satellite entity for originating from a satellite that broke up but also in perspective to eventually bake together a new satellite, just like all other planets and satellites evolved. Its a placeholder for a potential satellite if you like and it also has a mass and motion fitting Kepler's laws of planetary motion. Its an ongoing exploration and discussion. You can read about it in Kuiper belt and Oort cloud which can be regarded satellites of our sun or orbits with multiple satelites, maybe even planets, without one body dominating the part. In that you can also find the distinction, what is generally counted as planet, satellite, meteorite of a star- or planetary system and what is not: The origin of its matter and its orbit. --Kharon (talk) 21:30, 7 December 2017 (UTC)[reply]

It appears my confidence in the Roche limit was misplaced. According to [19], "If you broke up all the satellites within the Roche limit of Neptune, you'd get a ring system that would not look too terribly different from Saturn's." So this clearly is not a criterion to say they aren't moons. It is a good reason to watch your step on Larissa (moon)! (N.B. [20] says Larissa is inside the Roche limit while our article says it will break up someday when it passes it. Since Roche limit depends on density I'm not sure good sources don't disagree, but can someone confirm an error?) Wnt (talk) 22:00, 7 December 2017 (UTC)[reply]

Astronomy is a very bad science that is completely unable or unwilling to keep theory and facts separately. Just some weeks ago they found a super massive black hole so old that its assumed formation process can not be added up with the age of our universe according to the big bang theory. So maybe the big bang theory is bullocks but no one dares to say it out loud!! Its a very mainstream centered science like economics where you are either neoliberal or outcast (to put it slightly exaggerated). So don't expect to much! --Kharon (talk) 22:22, 7 December 2017 (UTC)[reply]

Well, if it's a choice between bad science in astronomy and bad science in our current Wikipedia draft I know which I find a priori most likely. ;) Wnt (talk) 22:37, 7 December 2017 (UTC)[reply]

The Big Bang is not bollocks, it's how'd it get from ~380,000 years after the Big Bang to galaxies that's not well understood. Sagittarian Milky Way (talk) 22:49, 7 December 2017 (UTC)[reply]

That's a new record in Dogmatism. Now even whole (known) galaxies must be wrong if they don't fit the mainstream. Btw. the mainstream core argument is not the background radiation but the Redshift. --Kharon (talk) 23:16, 7 December 2017 (UTC)[reply]

I suggest you work on your reading comprehension and check again what Sag has written. He comments on our incomplete state of knowledge, not any galaxies that "must be wrong". And while the redshift was one piece of evidence for an expanding universe, there were competing models - see Steady State theory. The CMB, on the other hand, is very well explained by the big bang theory (it's the red-shifted image of the surface of last scattering), but does not fit into e.g. Steady State. --Stephan Schulz (talk) 00:52, 8 December 2017 (UTC)[reply]

This is way off topic, but I should note [21] describes the black hole and links the original paper (I didn't check Sci-Hub though). It's 10% younger than the previous record holder. There's something there about "episodic hyper-Eddington accretion". I have no idea, but my gut feeling is it seems odd to say that a region of twisted space 800 millions times the mass of the sun forming in 800 million years would be perfectly logical, but 690 million years buggers all belief. Wnt (talk) 00:11, 8 December 2017 (UTC)[reply]

Modified Atmosphere Article -Clarification Questions & Suggestions

Hi,I am no expert in this subject, but thought I would give some feedback in the hope of making the article easier to read & understand. I was unable by clicking the Talk button to access anything other than my account page User talk:Mpe123

severity of preparation (give example to make the meaning clearer) does it mean something like processing such as washing salad or grating carrots?

A paragraph/comparison chart outlining the difference between EMAP and MAP could be helpful,to me they sounded pretty similar.(respiring product,permeability,"an equilibrium modified atmosphere will be established in the package and the shelf-life of the product will increase.")

When gas flushing & compensated vacuum are 1st mentioned (paragraph above scientific terms) it would be good to have a note mentioning that more details are given further in the article.

Isn't a potato a vegetable? I checked 2dictionary definitions & it says that they are vegetables "An example of a gas mixture used for non-vegetable packaged food (such as crisps)"

"breathable" films called EMAP are mentioned at the beginning of the article, but later(packaging films section) are referred to as "MA/MH films" are they the same?

Thanks in advance! — Preceding unsigned comment added by Mpe123 (talk • contribs) 17:58, 7 December 2017 (UTC)[reply]

Why isn't bitcoin mining causing the price of bitcoin to level off?

Bitcoin mining has now become hugely profitable at a bitcoin price of nearly $20,000. You could already make a modest profit at a bitcoin price of around $3000. So, why is the price going up and why isn't the bitcoin boom being accompanied by a boom in the sales of fast computer processors? Count Iblis (talk) 21:08, 7 December 2017 (UTC)[reply]

Maybe it's a function of Bitcoin being a scam. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:25, 7 December 2017 (UTC)[reply]
Bitcoin "mining" really is a misnomer. What is really going on is the creation of new blocks in the blockchain (each of which gives the successful creator a pre-defined reward). The bitcoin network automatically adjusts the difficulty of the block creation so that, on average, one new block is created every 10 minutes, independent of the total amount of compute power in the net. More miners spreads the same reward among more parties, but does not increase the supply. --Stephan Schulz (talk) 21:41, 7 December 2017 (UTC)[reply]

Your central assumption is wrong because the gratification for the mining is adaptive. There is no fixed rate like you would always get say 1 Bitcoin for solving/verifying a block. With the current high prize the gratification is most likely very very low now because there is only a limited number of blocks to be verified and many computers and computer pools try to solve one of these. Also if you add more computers and computer pools that is only more competition, more supply but not more demand, which is at the end essentially biting its own ass according to the rules of supply and demand. --Kharon (talk) 21:58, 7 December 2017 (UTC)[reply]

Are you replying to me or to the Count? The reward for mining is changing, but with a long-term predefined schedule - the reward is cut in half every 210000 "mined" blocks (which is once every couple of years). What is "adaptive" is the difficulty of creating a correct block (you need to find a nonce that will produce a hash with a given number of leading zeros, and that required number is adjusted to keep the rate of block creation roughly constant). --Stephan Schulz (talk) 22:11, 7 December 2017 (UTC)[reply]

No, i just saw an edit conflict and i did'nt want to rework it, in parts because of fearing to run into the next edit conflict and thus getting trapped into an adapting loop. --Kharon (talk) 22:31, 7 December 2017 (UTC)[reply]

One must be aware that the mining of Bitcoin gets you two kinds of money: the "Bitcoin mining" part where you create new Bitcoins that you get to keep, and the "transaction fee" part where people pay miners to validate their transactions in priority. I think I had read somewhere that the latter is what really gets you the money these days, but the only semi-serious source I could find is [22], whose numbers do not allow to compare the recent mining/commission parts in a meaningful way. Tigraan^{Click here to contact me} 10:19, 8 December 2017 (UTC)[reply]
While true, transaction fees don't increase the Bitcoin supply - they only move Bitcoin from one market participant to another. It may cause people to keep mining, even if the built-in rewards are no longer cost effective, but it has not direct effect on the supply/demand situation. --Stephan Schulz (talk) 11:27, 8 December 2017 (UTC)[reply]
Well, it does impact the supply and the demand of Bitcoin mining even if the impact on the Bitcoin possession market is limited, and the OP is explicitly about mining. (Maybe my indentation choice was questionable, since I was not really replying to your post after all.) Tigraan^{Click here to contact me} 12:22, 8 December 2017 (UTC)[reply]

Alternatively, many economists make the case that the price is overwhelmingly speculative, and is therefore detached from supply-and-demand economics. The actual availability of the "resource" - constrained by mathematical details, or otherwise - is no longer a contributing factor the market-price at which people are buying and selling.

Furthermore, fully 100% of the "bitcoin-to-dollar" conversion price is a snapshot of a secondary market - not "some" or "most," but fully all of that price is sustained on such a market. And it is an entirely unregulated secondary market! So this means that price arbitrage can occur with catastrophically enormous price-spreads - ratios that would be orders of magnitude larger than any other conventional marketplace.

In my opinion, I think I have composed my explanation using certain technical terms that are more ... shall we say, precise than the word "scam," but to the informed investor, these descriptions ought to carry equal weight.

For even more verbosity on the topic, here's Susan Athey, an economist specializing in internet commerce: Bitcoin Pricing, Adoption, and Usage: Theory and Evidence (2016). She's written several well-researched commentaries on bitcoin over the year. She couches her statements in even more jargon: given "the presence of frictions arising from exchange rate uncertainty," ... "the idea of bubbles seems salient for Bitcoin..."

Again, the language is florid but, in my reading, the implications are equally lurid. ...Scam.

To put it more bluntly: if you want to invest in bitcoin, just try to put a non-trivial amount of money (let's say, U.S. Dollars) into an exchange on some proverbial Monday; wait for the price to vary by some non-trivial amount; and try to get your money back out on the proverbial Friday.

See, in a regulated market, they have to give you your money. In fact, as of right now, in the United States, starting in 2017, they have to give it to you within two business days: this is called T+2 and it dramatically changed the financial marketplace this year - even though it got almost no media coverage outside of specialist investment and economics publications! But Bitcoin exchanges follow no such regulatory oversight. They can arbitrate your withdrawal, at any price, on any schedule. You won't be able to withdraw your proverbial investment return of 5%, or 50%, or 50000%, because the exchange maker sets the schedule for paying you.

The exchanges that convert bitcoin to hard-currency are ponzi schemes. What you will find is that you might be able to pull a few hundred dollars of "earnings" out of them, at a massively inflated price (so that they can sucker in the next guy with unrealistic inflated growth statistics). But macro-economics does not work via "a few hundred dollars." Even a 50x growth in an investment of a few hundred dollars still won't buy you a private jet! As soon as you attempt to invest any nontrivial amount of money, and try to reap your well-invested earnings, you will find your arbiter mysteriously goes bust in a bank run. This has already happened multiple times, but new suckers keep buying!

Nimur (talk) 22:36, 7 December 2017 (UTC)[reply]

I believe that @David Gerard: is something of an expert on cryptocurrencies. He may be able to weigh in here. --Jayron 32 01:17, 8 December 2017 (UTC)[reply]

The "boom"-part is nothing specific to bitcoin or other cryptocurrencies. There was a similar development in the Shadow banking system and we all read about how some companies that serve the tax havens lost their pants lately and what became visible. Behind all of this is a world financial system which contains more wealth than the whole world industrial economy can craft in 100 years.[23] One obvious side effect of this is a flood of "investors" desperately trying to put their wealth somewhere "save". Even a 10-year German government bond with negative interest rates was sold out in hours. There is going to be a huge financial "bloodbath" somewhere again soon and bitcoin looks like build to survive it almost as save as German government bonds. --Kharon (talk) 03:15, 8 December 2017 (UTC)[reply]

A few exchanges, including Coinbase, one of the largest, are regulated. Of course, I have no idea what kinds of standards are enforced by the regulators or how strictly they are enforced. Also, although it's true the vast majority of Bitcoin holders hold Bitcoins through a broker, Bitcoin intentionally doesn't require this. You can run Bitcoin wallet software on your computer and transact directly with others. Of course, then you are taking on the settlement risk yourself. --47.157.122.192 (talk) 03:19, 8 December 2017 (UTC)[reply]

Purely addressing the computing aspects of this: it's impossible to make a profit anymore mining Bitcoin on general-purpose CPUs, assuming those are what you mean by "fast computer processors". All "serious" Bitcoin mining today is done with custom hardware based on ASICs designed for the Bitcoin algorithm. Have you checked the price of those? --47.157.122.192 (talk) 03:19, 8 December 2017 (UTC)[reply]

A sharp rise in the price of tin has resulted in the re-opening of a mine in Cornwall. However, one mine which isn't going to be opened is this one: [24]. 82.13.208.70 (talk) 11:38, 8 December 2017 (UTC)[reply]

I'm calling a major ^{[citation needed]} on your claim that the surge in bitcoin pricing is primarily because people are looking at a safe haven. Sure it may have originally been a factor, but while I guess there may be a few who agree with you, most experts on economics question whether it's a significant factor with the current insane rises, generally suggesting as Nimur said it shows all signs of a bubble. Let's not forget other safe havens have not experience anything even close.

At a basic level, it's not that hard to understand either. If something has risen 10x in a few months, it's easy to see the attraction. If you'd only put $10k in it not long ago, you'd now have $100k. You've already missed the part of the boat, you don't want to miss the whole thing. And even those predicting doom are generally reluctant to say the value isn't going to go 10x more before there's a correction.

While Nimur had some points about the state of the market, I haven't seen strong evidence that you really can't get in or out as long as things stay as they are and you're not talking about too much money. (E.g. I'm not saying the Winklevoss twins could really easily get their $1 billion or whatever it is now.) Sure you may lose a silly amount compared to what you feel you should get but if you spent $10000 and are now getting $80k that's still a great deal. You're fine as long as there's enough suckers, er other people, who want to get in. When the shit hits the fan is if the value does collapse. You could easily find your $10k (or whatever) nearly gone.

But even then, this doesn't even mean that it's always a bad idea. The evidence suggests plenty of people who do think it's a bubble and fairly experienced investors are getting in, treating it similar to other high risk high reward things like VC. If you have enough money you can afford to put some in with the hope you'll get lucky and get out before it collapses. You have several different investments of the sort and you just need one to pay off for it to have been worthwhile. The issue is those who don't really understand the risks and are putting money in they can't actually afford to lose (or would otherwise be better places to be choosing less risky investments).

Nil Einne (talk) 12:06, 9 December 2017 (UTC)[reply]

The answer to the original question: bitcoin "mining" is actually on an approximately predetermined schedule of one block every 10 minutes (average), and whoever figures the block first gets the mining reward (12.5 BTC). Throwing more computing at the problem mines faster very temporarily - because every 2016 blocks, the mining difficulty is adjusted to be approximately every 10 minutes again. So, mining is an evolutionary arms race.

But this won't supply more bitcoin to drive the price down, because it's a somewhat-regular release of bitcoins - David Gerard (talk) 20:44, 8 December 2017 (UTC)[reply]

So is it more likely to mine a bitcoin at certain times like northern hemisphere summer (since the cost of computer cooling's higher there) and the 4th of July (since that's when the most populous rich country has its only major summer holiday)? (are there any miners that *don't* run 24/7/365? since they're pro now and have big hardware investments to recoup) Sagittarian Milky Way (talk) 21:12, 8 December 2017 (UTC)[reply]

Cooling does not add much cost difference. For example common mining/3D graphics cards need 250 watts and only 5-10 watts are needed for the cooling fans. The main factor is the price of electrical power which is why the biggest farms work in cooperation with a local power plant and why they are only located in countries like china and island, where electrical power is very cheap. That is also why most amateurs dont stand a chance in the long run unless they produce their own power very cheap. --Kharon (talk) 05:47, 9 December 2017 (UTC)[reply]

While you're right that power usage of the components tends to be significantly higher than the cooling costs, it definitely can be a factor. That's why you get things like [25] [26] [27] [28] [29] (the last one deals in particular with bitcoin). Just because you can get away with just leaving your desktop computer (which is probably idle most the time anyway) in your house with just the HSF doesn't mean it works at a large scale. Of course if your house uses AC you probably are paying for it anyway albeit it's likely almost lost in the noise if you just have a one or two computers which are idle most of the time. Of course as others have noted no one uses GPUs for serious bitcoin mining now anyway. Nil Einne (talk) 11:47, 9 December 2017 (UTC)[reply]

The price of electrical power for heavy industries is below 20 USD/MWh in Iceland.[30] [31]. 75% renewable energy there - mostly geothermic. --Kharon (talk) 15:24, 9 December 2017 (UTC)[reply]

What does that have to do with anything? The only source I linked to which talks about Iceland mentions that the price of power, the use of renewable energy and the cool climate are all factors. All the rest do not deal specifically with Iceland, including the one which talks specifically about Bitcoin. It's true that a number of them are dual use cases i.e. by reusing the heat you could reduce the cost by getting someone to pay for the heating, although it's clearly not happening in some cases e.g. the Norwegian one it's mentioned there's no charge to the people with the devices other than an initial setup cost. Maybe a per use cost is/was the long term plan, but as some of the other sources demonstrate, the cost of cooling is often a factor in large data centres so simply getting rid of the heat without having to pay can be useful. You haven't shown any sources that the cost of cooling isn't a factor or that it only adds 5-10W for cooling fans in large scale use, as you implied. As I said, you seemed to make the mistaken assumption that what works with a computer at your home (which is probably idle most of the time anyway) works when you have a lot of devices in a small area with very high constant use but it doesn't. And as I also said even with the home case it's not necessarily true that the only cost comes from running the fans, it probably doesn't if you have an AC. Nil Einne (talk) 07:11, 10 December 2017 (UTC)[reply]

December 8

Please identify a weapon

What is this weapon mounted on a Ugandan Army Casspir APC? I suspect is is a type of light mortar or grenade launcher. Roger (Dodger67) (talk) 09:00, 8 December 2017 (UTC)[reply]

My best guess would be the QLZ-87 grenade launcher. Mũeller (talk) 09:20, 8 December 2017 (UTC)[reply]

Perfect match, thanks Mũeller, and I see Uganda is known to be a user. Roger (Dodger67) (talk) 12:05, 8 December 2017 (UTC)[reply]

Cheese Curd

From Cheese Curd:

   Most varieties, as in Ontario, Quebec, Nova Scotia, Vermont, or New York State, are naturally uncolored. The American variety is usually yellow or orange, like most American Cheddar cheese, but it does not require the artificial coloring.

So what's making American cheese curd yellow or orange, if no artificial coloring is added? Is it because of some difference between Canadian milk and American milk? Or some other factor? Mũeller (talk) 09:17, 8 December 2017 (UTC)[reply]

Annatto.--Jayron 32 09:21, 8 December 2017 (UTC)[reply]

Missing the point that Annatto is a plant pigment, not synthetic, so a rewrite is required. Roger (Dodger67) (talk) 12:07, 8 December 2017 (UTC)[reply]

Square signal as only clock signal?

We have so many signals like triangular, ramp, unit step, impulse, square, etc. Why do we use only square signal for the clock signal in digital electronics? Sunnynitb (talk) 13:59, 8 December 2017 (UTC)[reply]

For the same reason that the time "pips" on the radio are short and clear rather than fading in from no sound over a 30 second period. There is a definite sharp step that can be used to trigger events. -- Q Chris (talk) 14:28, 8 December 2017 (UTC)[reply]

Thank you for your reply, but I didn't get it. Please, if possible, explain it a little bit or provide me some link regarding this. Sunnynitb (talk) 15:27, 8 December 2017 (UTC)[reply]

The purpose of a clock signal is to ensure that several events occur at exactly the same time. A number of different electronic components receive the clock signal, and each of them performs an action at a certain point in time based on the clock signal. Suppose the clock signal were a triangular wave, and the components were supposed to perform their action at the peak of the clock wave. It would be difficult for the component to tell exactly when the clock signal was at its peak, because the voltage a short time before the peak or a short time after the peak isn't much different than it is exactly at the peak. So one component might perform its action a significant amount of time before or after another one. A square wave has the desirable property that the signal changes very quickly at the point where the wave rises and at the point where it falls. So if all the components are watching for when the clock signal changes, they will all detect that event at nearly the same point in time. CodeTalker (talk) 17:44, 8 December 2017 (UTC)[reply]

And squares enable this at double data rate unlike other sharp-jumped waves like sawtooth waves. This is used for instance to make RAM since c. 2000 twice as fast as it would've been otherwise. Sagittarian Milky Way (talk) 18:05, 8 December 2017 (UTC)[reply]

adding to the answers above, many components are allergic to slowly-changing signals. they can latch up in some indeterminate state (metastability) or begin to oscillate. read any datasheet for a digital IC, it will specify maximum rise and fall times. 78.53.108.2 (talk) 23:35, 8 December 2017 (UTC)[reply]

Digital logic doesn't like inputs that are in an intermediate state - it tends to turn on two transistors, one pulling the next state high, and the other the same next stage low. This increases power usage, and can overheat the device. In addition, most loigc circuits use the rising (or falling) edge of the clock signal, rather than the actual high (or low) period to trigger the event. LongHairedFop (talk) 11:49, 9 December 2017 (UTC)[reply]

current mass ULAS J1342+0928

The mass of the black hole is given as 800 million solar masses. Since the light that this object is seen by is from 13 billion years ago, how large could we expect its mass to be now? I suppose in this time it has had a chance to merge/collide with galaxies.144.35.114.190 (talk) 14:57, 8 December 2017 (UTC)[reply]

Supermassive black holes (the technical term) can have masses of tens of billions of solar masses (at least several percent of the galaxy they're in). Sagittarian Milky Way (talk) 15:20, 8 December 2017 (UTC)[reply]

Though reading that article carefully, it does also say that the theoretical maximum is around 50 billion solar masses, as the rate of growth slows above 10 billion. Of course, there is also the possibility that it no longer even exists!

How could a black hole disappear? (besides Hawking radiation, which would take way more than the current age of the universe for an 800 million solar mass black hole) Sagittarian Milky Way (talk) 23:29, 8 December 2017 (UTC)[reply]

Seemingly odd it does not matter how big a black hole is - the gravitation is the same - equal to the speed of light. So in itself a tiny black hole has the same potential to grow as the biggest black hole we will ever find. It depends how much mass is in its reach and how much time you calculate for the grow. 13 billion years seems allot but if you put the Galactic year into perspective our home galaxy just made 58 turns in 13 billion years. Also galaxies are usually separated by millions of lightyears of empty space between them. Not that much traffic locally unless you are really close to something. If that giant black hole ate its own galaxy it might need another 500 billion years for another galaxy to cross its path.

Additionally odd is that according to its mass it seems to have already eaten a few hundred million suns aka every thing around it, if you consider only very, very, very few stars are as big or bigger than our 640 lightyears close neighbor sun Betelgeuse, which has 11.6 times or VY Canis Majoris estimated at 17±8 times the mass of our sun (see List of most massive stars). That is why there seems no possible explanation how a black hole could accumulate so much mass just a few hundred million years after the so called big bang. --Kharon (talk) 04:52, 9 December 2017 (UTC)[reply]

The speed of light escape velocity defines the black hole. If it was less light could escape and it wouldn't be a black hole and it'd just be matter, not some crazy thing that bends reality to the degree it can only have spin, change and mass. That's like saying strange how all the boats weigh as much as the water they displace. Well duh. Sagittarian Milky Way (talk) 05:29, 9 December 2017 (UTC)[reply]

There is so much wrong in this comparison that i feel the urge to look for the biggest book about physics i can find, to slap you with that until i fall asleep from exhaustion. --Kharon (talk) 08:28, 9 December 2017 (UTC)[reply]

Bytownite - industrial uses?

Does Bytownite have any industrial uses? Thank you, DuncanHill (talk) 15:11, 8 December 2017 (UTC)[reply]

According to this, No. --Jayron 32 15:33, 8 December 2017 (UTC)[reply]

In general plagioclase feldspars are very common and have some routine industrial uses like ground up in ceramics or used for gravel. [32] But it isn't very common; also, the alkali feldspars are apparently used more than plagioclase. [33] Apparently feldspar is used in ceramics at 20-25%. [34] Amusingly, someone is tracking this conversation elsewhere [35] and thinks the rarity works against it. The one thing I know it's being used for "industrially" is that some people are selling samples supposedly for healing chakras and such. Not sure how much of an industry that is. ;) Wnt (talk) 17:33, 8 December 2017 (UTC)[reply]

The "Duncan Hill" who asked the question on MinDat is the "DuncanHill" who started this thread. Neither of me is the IP who originally asked on the article talk page. DuncanHill (talk) 18:03, 8 December 2017 (UTC)[reply]

Could x moles of acid or base stochiometrically react with more liters or molarity of reactant if it's added quicker?

(at least up to a point) If there's never much more acid/base concentration in the reactant container than needed to cause a reaction to happen (cause it's added as slow as it's used up) then might it stop after less reactant than if the acid/base is added all at once and the initial concentration's much higher? Or does it all even out by the end so it doesn't matter much as long as "all at once "is still reasonably civilized (no exploding, decomposing, boiling, igniting, large temperature rises etc.) and "slower" isn't so slow that something like evaporation or oxidation changes the nature of the reaction much? Sagittarian Milky Way (talk) 20:19, 8 December 2017 (UTC)[reply]

Given my PO's advice, I am not going to hat this, but are you seriously asking whether one should combine an acid and a base quickly? You'd probably not just be failed out of high school chemistry, but you expelled and your teacher fired. This sort of BS question really doesn't belong here. Do you contribute to WP, or are you simply WP:NOTHERE? μηδείς (talk) 22:03, 8 December 2017 (UTC)[reply]

It doesn't have to be a strong acid and a strong base, it could be supermarket vinegar and baby teeth or those drain cleaners that take hours to work and clogs. I think it doesn't matter with acid/base neutralization anyway since titration's very accurate (but you're the expert). Even so, I've poured baking soda straight into supermarket vinegar and didn't have <10 fingers when HS chem teacher got tarred and feathered. Sagittarian Milky Way (talk) 22:24, 8 December 2017 (UTC)[reply]

I can picture something different happening if some extra reaction could occur at an extreme pH value. For example, if you have a sodium carbonate (Na2CO3) solution and you slooooowly drip in less than one equivalent of hydrochloric acid while stirring rapidly, I would expect you to end up with a nice buffer of sodium bicarbonate (NaHCO3). But if you pour in the HCl all at once without stirring, then that NaHCO3 will go fully to carbonic acid (H2CO3), which then can release carbon dioxide (CO2) by eliminating water (H2O). If much of the carbon dioxide bubbles away into the air, then you would have to keep stirring for a very long time indeed to reverse that (by picking up traces of CO2 from the air, which happens, but would continue to happen past the original equilibrium point). However, in this case, and I think in most others like it, exposure to concentrated acid effectively reduces the expected effect of the acid (in this case production of sodium bicarbonate), because (in this case) one proton is used up getting rid of the product that was created by another. Wnt (talk) 01:50, 9 December 2017 (UTC)[reply]

Using air bubbles to stabilize a ship

Cruiseships use stabilizers that act like wings to counteract the rolling movement of the ship. Would it be possible to get a similar result by using airbubbles? So, when a wave comes from starboard and the ship starts to tilt to portside, the ship would pump out air on starboard to decrease its buoyancy on that side? Joepnl (talk) 21:48, 8 December 2017 (UTC)[reply]

Any company that did this would open up its owners to liability for negligence if it sank, given that sinking due to loss of buoyancy is a well-documented factor. It's like telling your anger management patient to drink. μηδείς (talk) 21:58, 8 December 2017 (UTC)[reply]

I can't think of a single invention that wouldn't raise eyebrows in the legal department before it got implemented. Joepnl (talk) 00:21, 9 December 2017 (UTC)[reply]

The rolling motion of a ship is not caused by wave action. It is an oscillatory motion that represents conservation of mechanical energy - similar to the motion of a pendulum. When the ship's mechanical energy is too great it manifests as a rolling motion of excessive amplitude. The solution to the problem is to reduce the mechanical energy by using a force (or torque) that does negative work on the ship; and this is the function of the hydrofoils (also called stabilizers). Dolphin (t) 00:30, 9 December 2017 (UTC)[reply]

How would a ship roll if there are no waves? Look out of the window on a ship. Waves: the ship moves. No waves: the ship doesn't roll or pitch. I had the absurd idea that removing messages from trolls was OK but apparently it's not. Joepnl (talk) 00:58, 9 December 2017 (UTC)[reply]

A ship rolls at its natural frequency which is usually different to the frequency at which swells and waves arrive at the ship. Swells and waves will excite the rolling motion of a ship, but other things can do so too. For example, the wind blowing through the superstructure can excite the rolling motion even though the wind is steady in speed and direction rather than oscillatory like swells and waves. It is true that large swells and waves will excite strong rolling motion, but it isn't true to say that if there are no swells or waves there will be no rolling motion. Dolphin (t) 01:13, 9 December 2017 (UTC)[reply]

We were discussing "The rolling motion of a ship is not caused by wave action". Yes there are other possible reasons, including winds, asteroids, and fat people running starboard but those are not the main reason a ship moves. Joepnl (talk) 01:44, 9 December 2017 (UTC)[reply]

Movement of cargo could cause a ship to roll.194.126.80.63 (talk) 01:04, 9 December 2017 (UTC)[reply]

Do you mean list or roll? And @Joepnl: who's the troll? If they're blocked, revert'em. μηδείς (talk) 01:10, 9 December 2017 (UTC)[reply]

December 9

Is there a way to know that NASA didn't know about an asteroid?

I just spotted a sensationalist news article ([36]) that an asteroid capable of "destroying New York City" went past the Earth at a third the distance to the Moon, and NASA didn't detect it until it was headed away. They accept the explanation that NASA simply missed spotting the asteroid before that -- they are supposed to have found most of them but of course never all of them.

But of course, I can think of another potential interpretation. Maybe NASA knew it was coming but couldn't be sure it was really going to miss Earth, and stayed mum about it. Possibly some senior politicians were given a chance to shelter, but the general proletariat needs to work, not panic, right?

So... is there a way to post mortem what happened? Can you look at the asteroid's trajectory, look up how NASA did its scan, and say oh, it went here before they looked thataway and after they looked thataway? I would imagine that some post mortem would be expected to come out in a case like this. Wnt (talk) 01:38, 9 December 2017 (UTC)[reply]

If NASA failed to tell us something, it will eventually come out. But how would widespread panic have served anyone's purpose? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:49, 9 December 2017 (UTC)[reply]

hehe, you remind me of the guy with the bullhorn at the World Trade Center who told the cubicle drones to get back to work. "نفديك بالروح وبالدم", American style, eh? Wnt (talk) 02:06, 9 December 2017 (UTC)[reply]

"We give you soul and blood"? What has that got to do with anything? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:47, 9 December 2017 (UTC)[reply]

There's a rather creepy tradition in the Middle East of people chanting that they sacrifice their blood and their souls to (some leader). In the WTC I guess it was the corporation. And here, well ... a lot of little people have to keep going about their lives if the big shots are going to catch their cab and their plane to the deep shelter, no? Wnt (talk) 18:11, 9 December 2017 (UTC)[reply]

All of NASAs data is public domain, and nearly all of it is regularly published on publicly available scientific repositories. In particular, the data of the various sky surveys is available. Space is big and asteroids are small, often dark, and fast - we cannot constantly scan all of the heavens all of the time. Any data will first be seen by some random NASA scientists, not by upper management. Just imagine how big a conspiracy you would need to keep such a thing secret. Then read On the Viability of Conspiratorial Beliefs. --Stephan Schulz (talk) 01:57, 9 December 2017 (UTC)[reply]

This is what I would hope. But is the data really being reviewed by random scientists like Lowell looking at glass plates, or do all these sky surveys go into a big computer program that spits out candidates ... and might omit some, leaving those who think they control it none the wiser? Wnt (talk) 02:08, 9 December 2017 (UTC)[reply]

At max brightness (c. 6:30a EST) it wasn't especially dim and not far from the anti-Sun, the Moon was 65% full and less than 90° away but not especially close, it was over 13 or 14°N latitude which isn't very inconvenient and near the plane of the solar system which is the most likely plane to look for asteroids. However it wasn't discovered till November 10th but it's designation is still only 2017 VL2. This means 2017 VA to VH and VJ to VZ were discovered some time time after October (by definition), then the second cycle (2017 Vx1), then half of the third. This has continued for a third of a thousand cycles in a dark V half-month which means very few minor planets were discovered before it this November. The 5 or 6 days before W half-month began saw 13 times more asteroids discovered than the other 9-10 days. This suggests that asteroid survey activity sharply drops off around Full Moon even when it's not close enough to full for avoidance of moonlight and twilight to be impossible (one of the best places to see it would've been Guam, it wouldn't have been that much harder to find (at a different time of November 9) for much of the big observatories outside Asia-Pacific though). If any amateur astronomers saw it they might've thought it'd already been discovered and didn't call it in. Amateur astronomers have a much harder time discovering asteroids and comets than say 2000 or 1995. There's lots of computer surveys now that I think automatically tag all moving objects based on whether they've discovered. It'd still require any amateur astronomer who saw it on the 9th to not be interested enough in a not that dim moving pretty fast (so near Earth) to look up what it is and then discover it's not discovered yet. They'd also have to not keep up with contemporary near-Earth asteroid flybys. If they did they'd probably wonder why they hadn't heard of a bright asteroid this fast and look it up and become the discoverer instead (emailing its coordinates to the Bureau of Astronomical Telegrams (is it still called that?) should make NASA know about it) Sagittarian Milky Way (talk) 05:17, 9 December 2017 (UTC)[reply]

CENTRAL BUREAU FOR ASTRONOMICAL TELEGRAMS STOP --47.157.122.192 (talk) 18:28, 9 December 2017 (UTC)[reply]

I stupidly ~~rad~~read the story when I saw it somewhere else before you linked to it. Well I mean I read the first few lines. It quickly became clear it was utter nonsense. As with all Daily Mail (edit: well I wasn't sure it was DM when I clicked but strongly suspect it was) stories it's sensationalistic, missing the point that this sort of thing isn't exactly a rare event. We're finding out all the time that something got slightly close to earth and we only just realised a few weeks or months later. (Edit: And those are the ones we know about!) Many people ~~thing~~think we need to get better at detecting these things sooner, although they often also acknowledge in some ways there's probably little ~~point~~actual advantage at ~~the~~this time since silly action movies aside, if we do find something headed here even in good time there's probably little we can do with ~~out~~our current level of tech. Nil Einne (talk) 12:12, 9 December 2017 (UTC) edited at 06:48, 10 December 2017 (UTC)[reply]

It's worth noting that we could be doing a lot more to spot asteroids that might threaten Earth, like putting a telescope between Earth and Venus, but we don't because there's no political will to do so. Few people vote based on candidates' positions on asteroid defense. Of course, "conspiracy theories" are non-falsifiable, so maybe there is one there but the data is only made available to the Secret Conspiracy, and maybe they have plans to escape to their secret NASA child sex dungeons on Mars, and so on and so on. --47.157.122.192 (talk) 18:28, 9 December 2017 (UTC)[reply]

It's also worth noting that NASA's purpose is about space travel, space probes, airplane technology and things like that, not particularly about searching for asteroids. Here's a page of theirs about the sort of things they're working on currently. --69.159.60.147 (talk) 07:40, 10 December 2017 (UTC)[reply]

Big bang and size of the universe

At the Big Bang, the entire universe (as i understand) is thought to have been contained by a singularity. Does that imply that the universe as it now exists cannot be infinite? or could the singularity have contained an infinite universe within it? rossb (talk) 09:35, 9 December 2017 (UTC)[reply]

No, it doesn't imply it can't be infinite. There's a really simple "toy example" that shows this.

Suppose the universe at the current comoving time (let's normalize in such a way that the current comoving time is 1) is described by a standard Cartesian coordinate system — every point has (x, y, z) coordinates. And then suppose that, for particles moving along with the Hubble flow, at any time t before the present (that is, t<1), if the particle has coordinates (x, y, z) now, then it had coordinates (tx, ty, tz) at time t.

Then you can see that the universe is infinite, and was infinite at every time t>0. However, at time t=0 (that is, the exact instant of the Big Bang), all particles were at the same point.

It's a little hard to visualize the discontinuity, but luckily enough you don't have to. In practice cosmologists (almost) never talk about the exact moment of the Big Bang. They can talk about what happened 300k years after it, or a second after it, or 10⁻³⁵ seconds after it, but the Big Bang itself, no, they just don't touch that, usually. Could be it never happened at all; could be that time is an open interval that omits the instant of the Big Bang.

Of course there are all sorts of things wrong with the toy example in terms of relativity and known cosmology; it's not meant to be a serious proposal as to what happened. But it does show that the gross description of the Big Bang does not rule out an infinite universe. --Trovatore (talk) 10:28, 9 December 2017 (UTC)[reply]

I think this is the way to visualize the boundless universe. Let's say we live in a Universe of such a size that we cannot detect its boundary. Then all of a sudden a Big Bang happens here, right in the middle of our existence in such a way that every point of the space becomes a singularity. They all begin to expand and one of them will have all anthropomorphic parameters like our current Universe and eventually become populated by life forms. AboutFace 22 (talk) 16:11, 9 December 2017 (UTC)[reply]

No, I don't think that scenario (whatever it even means) is remotely responsive to the question. Mine, on the other hand, is. --Trovatore (talk) 20:03, 9 December 2017 (UTC)[reply]

The notion of the universe emerging from a singularity was put forth by Hawking and Penrose in 1970, and they have since abandoned it as incompatible with quantum mechanics when the universe was the size of the Planck length. The question as posed is decades out of date. μηδείς (talk) 23:08, 9 December 2017 (UTC)[reply]

Cold-tolerant trees

How do woody plants survive the winter in cold climates? Consider taiga forests, which typically experience temperatures far below freezing. Xylem#Evolution (one of the longest non-table sections I've ever seen in an article) mentions how some plants are able to tolerate the effects of freeze-thaw cycles on their physical structures, but I'm more wondering about water and nutrient transport: when things are frozen, how does anything move? Ice can't be transported, in particular; I would imagine that a frozen tree would die for lack of water, but obviously that doesn't happen with your average healthy tree. Nothing else in xylem, and nothing at all in phloem, as far as I could see. Nyttend (talk) 17:04, 9 December 2017 (UTC)[reply]

How do Trees Survive Winter Cold? by Michael Snyder, Commissioner of the Vermont Department of Forests. Alansplodge (talk) 18:05, 9 December 2017 (UTC)[reply]

Alan's link is good, it's largely about antifreeze, and note that there just isn't much transport going on in the Taiga during winter. Our best general article is at Cold_hardening (And is understandably kind of hard to find if you don't know what they call it. Maybe you can link it from a relevant section of the other articles?). Hardiness_(plants)#mechanism is fairly useless. Antifreeze proteins are a big part of it, see e.g. here [37] for recent scholarly work. SemanticMantis (talk) 18:08, 9 December 2017 (UTC)[reply]

Critical is the part about water being relocated to storage organs; I wasn't aware that this was an issue. I guess I shouldn't be surprised by the lack of nutrient transport, since girdling doesn't kill a tree immediately (and deciduous trees survive temperate winters without leaves), but I was completely unaware of this stuff. Thanks a lot! Nyttend (talk) 22:21, 9 December 2017 (UTC)[reply]

Why isn't northern Vermont covered in ice?

New York City was covered in ice 20000 years ago. Since then, the Earth has warmed up 9°F.

At present, according to the cities' Wikipedia articles, New York City has a mean temperature of 55°F, and Burlington, VT has a mean temperature of 46°F, a 9°F difference.

This means that New York City 20000 years ago and Burlington, VT at present should have about the same climate with regard to temperature. Why isn't Burlington, VT (and southern Quebec) covered in ice like New York City was 20000 years ago? — Preceding unsigned comment added by HotdogPi (talk • contribs) 21:37, 9 December 2017 (UTC)[reply]

If temperatures warm, ice caps shrink and sea levels rise. Conversely, drop the worldwide temperature by 9°F, and increasing ice will lower sea levels, and oceanside cities like New York suddenly won't be on the ocean; the climate will be more continental because of the new inland location. Also, note that glaciers can exist where they can't form — since Arctic glaciers can spread southward, rising temperatures (and receding northern glaciers) mean that they have to travel a good deal farther to reach Burlington now than they did to reach New York before, even if the weather were similar. Glaciers won't always spread to adjacent places cold enough for them to tolerate (see #Ice-free northern Greenland), but they will in many situations. Nyttend (talk) 22:18, 9 December 2017 (UTC)[reply]

Also it seems hard for ice to survive for tens of millennia if the average annual air temperature was 46°F. Any precipitation in the summer would tend to be rain. These areas must've cooled more than the global average while the rainforests cooled less than the global average. Interestingly, global warming causes the poles to warm faster than the tropics. As a nitpick, only part of New York City was under ice at the last glacial maximum. Manhattan, the Bronx and the northernwestern halves of Brooklyn, Queens and Staten Island were under ice and the southeastern halves of those 3 boroughs weren't. There's no non-glacial ridge or something with this orientation and the ice limit parallels the 20000 BC coast so continentality may have something to do with the ice limit orientation. Sagittarian Milky Way (talk) 22:42, 9 December 2017 (UTC)[reply]

Imagine a simple world-model in which the average yearly temperature is 40 degrees F. That could be consistent a mild climate with six months of 30 degree temperatures, where the snow never melts, and six months of 50 degree temperatures, where the snow melts slowly. Or it could be consistent with an extreme climate, where the 'winters' are 0 degrees F, and the 'summers' are 80 degrees F. Note that the average temperatures are the same: (30+50)/2 = (0 + 80)/2 = 40; but in the extreme climate all the snow melts quickly at the beginning of the warm period, while in the mild climate, even though the winters are warmer, the snow melts much more slowly over the summer, and some ice packs can last all year, building into glaciers.

This seeming paradox arises because although the average temperatures are the same on a year-round basis, snow doesn't care whether it is 0 degrees F or 30 degrees F. It won't melt in either case. The only thing that matters is the summertime temperature--the average temperature is irrelevant. Hence knowing only the average temperature difference between NYC and upstate Vermont tells you nothing. What matters is the summer temperatures in those places. μηδείς (talk) 22:59, 9 December 2017 (UTC)[reply]

The current annual temperature range of NYC is at least 43.9°F (more if you use daily averages instead of monthly and July avg highs instead of July avg means). Do you have evidence for your implied claim that the average annual temperature range of NYC when it had glaciers (and extra continentality) might've been only 20°F? Without seeing the evidence it seems possible but unlikely. Sagittarian Milky Way (talk) 23:35, 9 December 2017 (UTC)[reply]

Whom are you addressing, SMW? You have indented under me, ask "Do you have evidence..." and mention 20°F that I see nowhere else in this thread. μηδείς (talk) 01:20, 10 December 2017 (UTC)[reply]

The way snow melts

I noticed that when the temperature rises above zero after a colder period, sometimes all that is left of a layer of snow, is where I walked through it, just a track of footprints made of snow.

Is it because compressed, denser snow is more resistant to the heat? Languagesare (talk) 21:50, 9 December 2017 (UTC)[reply]

~~Its mostly because normal "fresh" snow contains allot of air. Since air is a very good insulator it will slow down the complete melting. --Kharon (talk) 22:52, 9 December 2017 (UTC)~~ Wrong. Much more complicated. --Kharon (talk) 06:05, 10 December 2017 (UTC)[reply]

Are you saying that the footprints "compress" the air as well as the snow? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:09, 9 December 2017 (UTC)[reply]

Kharon seems to have misinterpreted the question, since the OP says that the unpacked snow melts, and only his footprints are left, not that the footprints melt and only the fresh snow is left. μηδείς (talk) 02:41, 10 December 2017 (UTC)[reply]

It may be that Kharon is from a place that rarely sees snow. You and I both have had plenty of exposure to snow, and the OP's question describes a familiar phenomenon. And the OP's answer-in-the-form-of-a-question is what I would assume to be the explanation. Snow that's more densely packed will tend to take longer to melt. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:22, 10 December 2017 (UTC)[reply]

Yes, I was wrong and i misunderstood the question. It seems compacted snow takes longer to melt. I tried to read up about that but most of the literature on snow and melting is focused on Glaciers. However one major accelerating factor for the melting process seems to be that the melting water from a melting surface will flow down easier into uncompressed snow, that way transporting the heat from the surface down faster the less compact the snow crystals are baked together or even transformed into polycrystals. --Kharon (talk) 06:05, 10 December 2017 (UTC)[reply]

United States map

Aaaarrrgh! Please help. I'm looking for a normal, high quality map of the US, like what you'd have on the wall. You know, a bit of topo, roads, cities, colours, that sort of thing. It is absurdly hard to find for me. Many thanks! Anna Frodesiak (talk) 22:18, 9 December 2017 (UTC)[reply]

Do you want to buy a physical map, or just have a machine readable one with a large size and a free license? You can also search google: https://www.google.com/search?q=united+states+map&dcr=0&tbs=sur:fmc,isz:lt,islt:4mp&tbm=isch&source=lnt&sa=X&biw=1280&bih=650&dpr=1.5 Graeme Bartlett (talk) 23:40, 9 December 2017 (UTC)[reply]

There's a company called WallPops selling through Walmart and Target that has National Geographic maps of the US for sale. They're about $15 dollars. Just Google it really. They're not hard to find.--Jayron 32 03:28, 10 December 2017 (UTC)[reply]

Actually, I just want to view it on the computer. I just want that sort of map. Anna Frodesiak (talk) 05:17, 10 December 2017 (UTC)[reply]

December 10

Towed array

What is the minimum depth under the keel which is required to safely deploy a towed array without it ripping away from dragging on the sea bottom? Is this depth the same for submarines and surface ships? 2601:646:8E01:7E0B:F9B4:9A86:7938:FC5D (talk) 02:14, 10 December 2017 (UTC)[reply]

No they aren't the same. Civilian towed arrays are a bit more sophisticated than their military counterparts, and can be actively flown at different depths, handy if a ship wants to cross your stern during a survey. I believe military submarine streamers are slightly negatively buoyant, I don't know about military surface ships arrays. In the days before solid streamers a big part of deploying a surface streamer was ballasting it to neutral buoyancy, since if a section dived the sea pressure would force the paraffin up, emptying the tube, encouraging a deeper excursion. Very messy. This is the design I worked on, I think http://www.ldeo.columbia.edu/research/office-of-marine-operations/seismic-equipment-and-operations

The depth is typically 10 m below the sea surface for a surface array. Greglocock (talk) 02:42, 10 December 2017 (UTC)[reply]

There are definitely many different types and some likely technically independent from distance to the ground. However an array must be roughly in one straight line, because the real water column is divided into Thermocline or thermal layers which de- and reflect acoustic signals like a Mirage or Fata Morgana can de- and reflect light. A "hanging" towed array would make it a challenge to keep the array in one of these layers and therefor massively reduce the arrays capability to detect sound sources, their direction and distance reliable. --Kharon (talk) 06:32, 10 December 2017 (UTC)[reply]

Submarine crew

How big is the engine watch on the Virginia-class submarines, and how many of them are officers and how many enlisted? (If this is classified, please say so and I'll cross this question out.) 2601:646:8E01:7E0B:F9B4:9A86:7938:FC5D (talk) 02:17, 10 December 2017 (UTC)[reply]

If it's classified, no one here will know the answer. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:19, 10 December 2017 (UTC)[reply]

People do things they regret, Bugs. https://www.theguardian.com/us-news/2016/aug/20/us-navy-sailor-jailed-for-taking-photos-of-classified-areas-of-nuclear-submarine http://www.foxnews.com/us/2017/01/25/pardon-me-navy-sailor-in-jail-for-submarine-photos-pleads-for-mercy-from-trump.html We can hope no one would share classified information, for their own sake. μηδείς (talk) 04:05, 10 December 2017 (UTC)[reply]

I googled "crew size of virginia class submarine" and found this top-secret US Navy website:[38] ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:50, 10 December 2017 (UTC)[reply]

Nitrate testing chemical

Two questions:

What chemical is used to conduct the nitrate test for freshwater from API?
What chemicals (or class of chemicals) could create a false positive?

Background: I tested my hand-me-down aquarium's water and the test turned cherry red within 30 seconds (which is bad). The Miata should be like 20 ppm, not 200+, given the bio load and time since water change. My thought was that a terracotta pot leeched something into the water (silicate most likely). Fish show no signs of stress which makes me think it's not actually nitrate. EvergreenFir (talk) 07:22, 10 December 2017 (UTC)[reply]