Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

October 5

What is this thing?

What is this thing?

Uploader has a local name for the bug. Claims a local discovered it. What is it? Magog the Ogre (t • c) 01:31, 5 October 2017 (UTC)

It's a caterpillar. Someone would probably need a location to get more precise than that.--Jayron32 01:34, 5 October 2017 (UTC)

The file description page on commons has some clues, including a precise location in Kenya. Jahoe (talk) 09:17, 5 October 2017 (UTC)

Description says it's a centipede, but it looks suspiciously similar to a Saturniid moth larva to me O_o Dr Dima (talk) 20:07, 5 October 2017 (UTC)

It is certainly not a centipede. μηδείς (talk) 23:51, 5 October 2017 (UTC)

Looks to me like a caterpillar which is starting the process of forming a chrysalis. That part near the bottom appears to be the start of this stage. Here's another species at about the same stage in chrysalis formation (the one on the left): [1]. StuRat (talk) 05:27, 7 October 2017 (UTC)

Slug moth caterpillars (family Limacodidae) look similar, but I'm not finding an exact match at Commons or even Google images.--Wikimedes (talk) 19:27, 8 October 2017 (UTC)

Slide-fire adapter

In the reports and commentary about the latest (at time of writing) American celebration of the Second Amendment mass-murder there are many mentons of bump stocks and slide-fire adapters. Bump stock is a redirect to an article which has some information about them (as well as lots of hints for anyone wishing to murder lots of people). We do not appear to have anything about slide-fire adapters. What are they? DuncanHill (talk) 21:00, 5 October 2017 (UTC)

More or less the same thing. "Slidefire" (the company) are one of the main makers of bump stocks.

One difference, in historical terminology, is that a bump stock requires a semi-automatic (self-loading) weapon. A "slide fire" technique was originally applied to manually-loaded weapons, particularly pump-action shotguns, with a poorly-designed, faulty or modified trigger disconnector. Holding the trigger down on these and racking them (working the loading slide) they would fire the trigger mechanism as soon as the breech went back into battery. Andy Dingley (talk) 21:58, 5 October 2017 (UTC)

Thank you, DuncanHill (talk) 22:18, 5 October 2017 (UTC)

The shotguns are also sometimes called slam fire. Here is a video that compares how fast you can fire the two types: https://www.youtube.com/watch?v=0-csrQ_VP5Y --Guy Macon (talk) 22:32, 5 October 2017 (UTC)

Off-topic: I find the little jabs in your question a bit insulting to a lot of people, especially when you say you really have no clue about what you're talking about. Please refrain from the superfluous comments in the future. Justin15w (talk) 14:40, 6 October 2017 (UTC)

Has anyone seen any other notable uses of bump stocks this week? I think defensive gun use claimed there were something like 33 million of them. Jimbo forfend that we would offend anyone using one! Andy Dingley (talk) 14:57, 6 October 2017 (UTC)

One doesn't need to have an extensive technical knowledge of firearms to have a valid opinion about mass murder and its enablers. DuncanHill (talk) 15:21, 6 October 2017 (UTC)

I think slamfire is the most relevant article here. @Andy Dingley: By the way, can you source a number of bump stocks in circulation? It strikes me that a potential way to numerically establish thresholds regarding "advanced" weapons is to take the number of innocent casualties (i.e. not suicides, not the shooter, but including any other 'incidents' we may have missed...) and divide by the bump stock * years to get some kind of threat evaluation, which then can be compared to figures like here for other phenomena (a 1/625 crash rate per 10 miles drunk driving, though we still have to do some heavy philosophy to decide if a per-year comparison is relevant. If we're going to argue about gun control on the science desk at least let's do it with some kind of numbers and theory. (There is a pro version of this at [2] but I have to discard it because their cost is based on lost wages, i.e. if someone invents a gun that can only shoot the poor that would be considered OK, but one that shoots the rich is not; note it is certainly possible to invent that sort of gun with facial recognition and a no-shoot list. I think a simple per-life number, presuming wounds are proportional, is far more productive) Wnt (talk) 05:48, 7 October 2017 (UTC)

October 6

Can electron quantum tunnel out of a black hole?

If a single hydrogen atom is just at the event horizon of a black hole. Can it's electron quantum tunnel from inside the event horizon to outside it. After all, its location is just a wave function and half of the wave is inside the event horizon and half of the wave is outside the event horizon. 110.22.20.252 (talk) 01:56, 6 October 2017 (UTC)

Hawking radiation is at least a bit relevant. Sagittarian Milky Way (talk) 02:15, 6 October 2017 (UTC)

Yes, there are generally theories that quantum mechanical effects will allow particles to escape from black holes, albeit with a very low probability. However, as we lack a comprehensive theory of quantum gravity or any direct experimental access to black holes, I would suggest such ideas are rather speculative at present. I would note though that unless you have some magic way of suspending matter right at the event horizon, then the atom is likely to be falling into the black hole at very high speeds. The amount of time that any atom might be considered half-in/half-out of the black hole is likely to be extremely small for any normal black hole. The situation is more interesting in the case of microscopic black holes, if such entities actually exist. It is possible to imagine, at least in theory, black holes so tiny that particles like electrons are essentially too large to fit in the black hole and even after being eaten there is an appreciable chance that they leak back out again. Again though, this all rather speculative and untested. Dragons flight (talk) 02:55, 6 October 2017 (UTC)

• Jak skazal SMW, see Hawking Radiation. μηδείς (talk) 00:50, 7 October 2017 (UTC)

What does jak skazal mean? Sagittarian Milky Way (talk) 01:18, 7 October 2017 (UTC)

Limit of temperature generated by electricity

Hi again ref desk, another impossible to Google question. I heard on a podcast about converting the world to renewables, that creating steel requires around 3000°F and they claimed that using electricity alone, you can't get to those temperatures. So, is this true? If so, given an infinite amount of power, is it a law of diminishing returns? I was thinking they could just turn large chunks of iron into filaments (however impractical) to accomplish this. Anywho, thanks in advance. Drewmutt (^ᴥ^) talk 04:35, 6 October 2017 (UTC)

No, not true at all. Our article on electric arc furnaces says that they can reach temperatures of 3,000 °C (5,432 °F). 2601:646:C101:C8A2:34D5:864B:CE64:F9CD (talk) 05:46, 6 October 2017 (UTC)

That just the furnace. The actual arc is hotter.

• "Electrical arcs produce some of the highest temperatures known to occur on earth, up to 35,000°F (19,426°C). This is 4 times the temperature of the surface of the sun which is about 9000°F (4982°C)."[3]

BTW, it took me roughly a minute on Google to find the answer to this "another impossible to Google question". I'm just saying. --Guy Macon (talk) 06:53, 6 October 2017 (UTC)

If you want people to Google better themselves, it would help if you included the search strings you used. Sometimes you have to know something about a subject in order to Google it effectively and it's hard to not end up with tangientally-relevant but much more popular results. --185.216.49.78 (talk) 11:42, 8 October 2017 (UTC)

(ec)Maybe we should also mention that many high-quality steels are routinely produced in electric arc furnaces (and have been for at least decades), because they offer more control over the chemical composition of the steel (there is no coal to introduce carbon, or other undesirable impurities coming with coal, like sulphur and phosphorous), and they also make the physical process easier to control. Of course there also is a red herring - just because it is hard to replace some fossil fuel applications does not mean that we cannot reduce carbon emissions to a sustainable level - most carbon emitting processes can be replaced or improved. --Stephan Schulz (talk) 10:00, 6 October 2017 (UTC)

• As pointed to above, the problem is not the maximum temperature. But a key consideration is that coal is used to bring not only heat but also carbon content to the steel in blast furnaces (historical note: Wootz steel), which can help the economics of coal vs. electricity - you would need a source of carbon if you heated by electricity.

Blast_furnace#Iron_blast_furnaces says that there have been electrical blast furnaces in Sweden but I cannot track down a source. I found this report considering switching to biomass (which counts as "renewable" by most standards). Tigraan^{Click here to contact me} 09:46, 6 October 2017 (UTC)

• I would also note this, from our article on Tantalum hafnium carbide: " Tantalum hafnium carbide is a refractory chemical compound with a general formula TaxHfy-xCy, which can be considered as a solid solution of tantalum carbide and hafnium carbide. Individually, these two carbides have the highest melting points among the binary compounds, 4,150 K (3,880 °C; 7,010 °F) and 4,201 K (3,928 °C; 7,102 °F), respectively, and their "alloy" with a composition Ta4HfC5 is believed to have a melting point of 4,263 K (3,990 °C; 7,214 °F). Very few measurements of melting point in tantalum hafnium carbide have been reported, because of the obvious experimental difficulties at extreme temperatures. " (Emphasis added) --Guy Macon (talk) 16:20, 7 October 2017 (UTC)

Global warming

So when people think global warming is made up, what is their reasoning for why they think scientist would just make it up? Is it just random conspiracy nuts? CTF83! 09:30, 6 October 2017 (UTC)

It's very much not random - it's carefully seeded by people and organisations that profit from the old-school carbon-based economy and want to reduce or delay changes. A modern classic on the topic is Merchants of Doubt, but you will find plenty of additional sources via Google Scholar. --Stephan Schulz (talk) 09:40, 6 October 2017 (UTC)

There are not many global warming denialists. Temperature is quite easy to measure after all. Denialists mostly deny it's man-made, and hence, believe nothing should be done.

They normally explain the consensus as a result of aggressive activism, as a Chinese invention, or whatever. See Global warming conspiracy theory for the whole story. --B8-tome (talk) 11:45, 6 October 2017 (UTC)

To be fair, those of us who grew up in the 1960s and 1970s were regularly served up gloomy scientific predictions; the world would run out of food or water (or both) at some time in the 1970s, we could be thrown back into the stone age by a power cut, we would completely run out of oil in 1984 and millions would die when the next ice age arrived early in the 21st century. So although I agree fully with what Stephan Schulz says above, there has been an awful lot of crying wolf beforehand, so some scepticism is understandable. Alansplodge (talk) 12:06, 6 October 2017 (UTC)

The reason I've heard is funding, that if global warming wasn't real, climatologists risk losing their funding. A Quest For Knowledge (talk) 12:15, 6 October 2017 (UTC)

Because as a rule scientists are motivated by money and choose their profession because scientific careers pay so well? Or because there is a hive mind controlling all scientists? Note that anyone who puts a serious dent into a widely accepted theory would be set for life - compare Albert Einstein (who killed Newtonian mechanics), or Barry Marshall and Robin Warren, who showed that most gastric ulcers are caused by infections, and not (directly) by stress and diet. --Stephan Schulz (talk) 13:37, 6 October 2017 (UTC)

It isn't just because it is in the interest of some very big companies, there is also a desire in people to not believe they are doing any wrong by driving cars or taking holidays by plane or any of the other countless good things of modern life that need fuel to be burnt. And in particular in America it basically says you can't be altogether free to do whatever you like which is one of the beliefs the country was built on. So lots of people are quite happy to engage in what psychologists call denial. Dmcq (talk) 13:55, 6 October 2017 (UTC)

As hinted above, there is a habit of grouping anyone and everyone who disagrees with anything at all about global warming into the "stupid denier" section. If I were to point out a prediction from Gore's Inconvenient Truth that didn't happen, I would immediately be as much of a denier as some guy who claims that it is all made up by the illuminati. 209.149.113.5 (talk) 17:25, 6 October 2017 (UTC)

That is simply not true. Scientists were quite happy to point out some problems with the film An Inconvenient Truth. They didn't however make the leap from that Al Gore made some mistakes in his film to that global warming isn't happening. Dmcq (talk) 15:37, 7 October 2017 (UTC)

Ok thanks all! CTF83! 17:30, 6 October 2017 (UTC)

It is because the vast majority of lay people (whether they have doubts about global warming or not), don't know much about how science works in practice. In particular, they lack knowledge about the rigorous review procedures. The way the media reports on science in general, not just about climate change, doesn't help. There is usually nothing in news reports about science that gives you any clues how the review processes work. Because usually the news media will try to interview the leading experts in the field, this then leads to a skewed picture of how science works, it then looks like professors ultimately decide what is going to be accepted as proven facts. Then some lay people will find that reasonable, while other people who have read elsewhere that all these professors are left wing liberal tree huggers, cannot be trusted, will have severe doubts.

Contrast this with the justice system. People know a lot more about the procedures of that system and the way the media reports about crime and court cases usually will contain something about the relevant procedures. Then, without even reporting about the details of the evidence that led to a conviction, most people will typically accept the verdict. In exceptional cases there may be doubts, but even in such cases were someone is alleged to have been wrongly convicted, will people still argue that there should be a retrial based on e.g. new evidence. So, people know about the procedures of the system and at most they would want a new hearing within the system. In case of global warming, the deniers buy into arguments presented outside the system and they want conclusions reached via the procedures of the system to be ignored. That's analogous to releasing someone convicted of murder based on a newspaper editorial without going through the procedures set out for that (e.g. appeal and retrial or applying for parole or pardon). Count Iblis (talk) 19:26, 7 October 2017 (UTC)

Is there a wikipedia article debunking the "Never Adjust for Curvature of Earth" claim of Flat Earth?

Is there a wikipedia article debunking the "Never Adjust for Curvature of Earth" claim of Flat Earth? Basically the stupid argument of flat earthers is that an aeroplane flying level on a spherical earth would fly off into space. Since the pilot of the plane NEVER adjust for curvature of the earth, the only conclusion a sane person can draw (with his kindergarten crayon) is an earth that is as flat as a pancake.

I know how to debunk it, it involves the vector from the centre of mass of the aeroplane to the centre of the earth. The aeroplane naturally balances itself on the centre of the mass, in the direction of the centre of the earth. So just imagine the aeroplane like a see saw with the pivot being the centre of mass of the plane. However it takes too much words, diagrams and effort to explain the idea to the Flat Earthers. So I am looking for a wikipedia article to explain this concept so that I can just direct them to the article. 110.22.20.252 (talk) 10:21, 6 October 2017 (UTC)

Gravity adjusts the plane for curvature of earth. That's like Earth is longeing the plane.

PS: I hope you don't meet many flat-earthers in your day to day. I have some just through the internet, and thought they were a parody of creationists. This was a classical case of Poe's law. --B8-tome (talk) 12:01, 6 October 2017 (UTC)

If those flat-Earthers admit the existence of gravity anomaly, it might be a starting point to argue that "gravity is not always vertical" (or rather, that if by definition vertical = in the direction of gravity, all verticals on Earth are not parallel), and the plane goes perpendicular to the gravity field, etc. But I am not sure of what is causing g in their world model, so... Tigraan^{Click here to contact me} 12:11, 6 October 2017 (UTC)

The Handley Page Gugnunc, flying very slowly downwards, whilst pointing clearly upwards

• There are a few effects here. Conservation of energy is one, things just don't change their gravitational potential energy unless there is some trade of energy going on. So planes don't change altitude against gravity unless they're either driven by their engines, they perform a zoom climb and trade speed for altitude, or light gliders might climb in a thermal.

Then there's the classic balance between lift and weight, thrust and drag. When these are balanced, there's no vertical movement (Note to Newton - there's no vertical acceleration because they're balanced. But there's also no vertical speed because of the work against the gravitational field).

Finally there's the angle of attack issue. Aircraft move vertically because of the lift/weight imbalance. But flat earthers think aircraft "go where they're pointed" and so presume that any aircraft pointing "up" flies in that same direction.

Underlying all of this though, is the flat earth refusal of either gravity (at all) or their belief that gravity acts parallel and perpendicular to a flerf, rather than symmetrically and radially. Andy Dingley (talk) 12:15, 6 October 2017 (UTC)

Wikipedia has an article Flat Earth but does not as far as I know address this claim. If you get a reliable source discussing it then you could try adding it somewhere I guess. However I don't see the point of the question. No flat-earther is going to be convinced by some rational scientific argument about what a plane does or gravity or whatnot if they think pictures of the earth from space are part of some conspiracy theory. Dmcq (talk) 13:48, 6 October 2017 (UTC)

Flight instruments#Altimeter would appear to be relevant. The pilot will use his instrumentation to ensure his craft is an appropriate distance above the ground. This is important because aircraft are segregated laterally and vertically. 92.8.220.234 (talk) 15:19, 6 October 2017 (UTC)

So do you follow the flat earth claim here? That aircraft only maintain altitude, rather than flying straight above an Earth curving away beneath them and so heading off into space, because the pilots are deliberately steering them downwards?

Perhaps we need an article on the legal fallacy of riding two horses as well? Globe Earth aircraft maintain a constant altitude as an equilibrium, because of gravity. The same gravity shapes the form of the Earth too, so we end up with a constant gravitational height approximating a constant altitude over a plain. This is the same case for both globe and flat earth models.

The fallacy of flat earthers claims about aircraft depend on two underlying fallacies. Firstly that aircraft climb "by pointing upwards", rather than by having an excess of lift. Secondly, a flat earth aircraft would fly straight and level above a flat earth, and a globe earth aircraft would follow the same altitude around a globe Earth. The fallacy is to claim that a flat earth aircraft, following flat earth physics, would somehow be above a globe Earth, dropping away beneath it! Aircraft over a globe Earth are flying by globe Earth physics. Andy Dingley (talk) 15:50, 6 October 2017 (UTC)

This is serious. This is NOT A LAUGHING MATTER. THIS IS SO SERIOUS THAT a man took a spirit level on an airplane to prove that the earth is flat. [Man takes spirit level on an airplane]. 110.22.20.252 (talk) 16:42, 6 October 2017 (UTC)

The easiest way to understand why a plane does not fly off the Earth is to consider the frame of reference fixed with respect to that plane. In such a frame the plane is not moving at all but instead the Earth rotates beneath it. The air follows the Earth and moves relative to the plane creating a lift that balances the total gravity force. So, it is not surprising that plane stays bound to the Earth. Such a frame is, of course, generally non-inertial save one special case. However one of the two inertial forces – centrifugal force – is just added to the true gravity forming the total gravity force and is essentially unobservable. The second inertial force – Coriolis force – is small (depending on velocity relative to the plane) although it will readily reveal itself once you conduct a Foucault pendulum test. Ruslik_Zero 18:26, 6 October 2017 (UTC)

You are not going to convince a flat-earther with rational argument. See Duty calls for what I think about your capital letters about that this is so serious. Dmcq (talk) 18:49, 6 October 2017 (UTC)

Flat-earthers don't believe in gravity; they believe that the earth is accelerating upwards at the rate of gravity. If you think the Earth is a globe because you can see the curvature of the horizon, try this: take a long pole that you know to be perfectly straight from sighting along it. Grasp it at its centre with one hand; hold that arm out in front of you at full arm's length so that the pole is horizontal and level with your eyes. Look at the hand. Do you see anything unusual about the pole in your peripheral vision? Explain that. Akld guy (talk) 21:15, 6 October 2017 (UTC)

Finely crafted Pan Balance or scales with boxed set of standardized gram weights.

Talk about the amount of ignorance of physics. 99% of the youtube videos explaining why the airplane does not fly off the earth in a level flight is COMPLETELY WRONG. Right result but wrong explanations.

• The air get more rare as the altitude increases, Therefore the airplane must curve with the shape of the earth. CORRECT STATEMENT but wrong explanation, I can prove this if you replace the plane with a rocket and take away all the air by moving it to the moon. A rocket with thrust (directed towards the centre of the moon) that perfectly balance out the force of gravity over the moon, will still curve with the shape of the moon. The air get more rare explanation is wrong.

• Gravity makes the airplane confined to a certain altitude above the earth. TRUE but how?

• The autopilot of the airplane keeps it curving with the earth. WRONG. The airplane will still curve even with no autopilot.

• The trim of the airplane keep it curving with the earth by keeping it "level with the horizon". WRONG. See rocket on moon explanation. Trim needs air to work on an airplane.

The true answer is that the airplane is like a (weighing) balance scale which naturally balances itself by the centre of mass located at the centre of the aircraft by the wings. As the airplane travels an infinitesimal distance to the right, the front of the airplane dips down an infinitesimal amount and the tail of the airplane rises up an infinitesimal amount. This is because the airplane is like a (weighing) balance scale or a see saw. As it moves to the right, the vector from the centre of mass of the airplane to the centre of the earth changes. So the airplane becomes "unbalanced" and like a (weighing) balance scale or a see saw, it will naturally rebalances itself to make it level according to the new gravitational field. You can say the airplane ALWAYS forms a right angle triangle from the front of the airplane to the centre of the airplane to the centre of the earth. You don't need autopilot and you don't need any other explanation. 110.22.20.252 (talk) 04:09, 7 October 2017 (UTC)

It actually is possible, in theory at least, to use an airplane to test for a flat Earth. If you have an east-west route near the Equator, the Earth gravity you feel is adjusted downward (normally) by 0.3% for centrifugal force. Thus, if you fly 500 mph East, you should weigh about 0.15% less (adding to your speed and the centrifugal force), and if you fly 500 mph West, you should weigh about 0.15% more. In concept an analytical balance can weigh things to this accuracy. The caveat is, I have a hard time picturing that the vibration typical of a commercial flight would actually let you weigh that precisely. But I've never taken an analytical balance on board a plane! (Probably get sent to Guantanamo Bay just to be 'on the safe side') Wnt (talk) 06:21, 7 October 2017 (UTC)

Well, the basic plan is good. With a 100kg reference mass, you should notice 300g of difference going one way or the other. To handle vibration, just take a time series for each leg and average the results. There are two caveats: A balance (in the narrower sense) is useless, as the same reduction applies to the reference weights. You need a good weighing scale that directly measures force. Also, using yourself as a test mass is not a good idea - even if you skip the aircraft food (a small sacrifice, ok), it will be hard to maintain exact weight for a sufficient time, due to sweating and breathing. --Stephan Schulz (talk) 06:47, 7 October 2017 (UTC)

Wups, clearly you're right about the analytical balance - I should watch those last-minute "improvements". And no, you couldn't literally use yourself for a test mass... not unless you're one of those new robotic airline pilots, anyway. Wnt (talk) 10:49, 7 October 2017 (UTC)

Name of 'Bill Gates just walked in the room effect'

How would you call the statistical effect on income/personal wealth colloquially called 'when Bill Gates just walked in a room'?--B8-tome (talk) 11:41, 6 October 2017 (UTC)

?? [4]? Andy Dingley (talk) 12:04, 6 October 2017 (UTC)

• This is related to the Ecological fallacy - the mistake of making assumptions about individual members of a group based on group averages. That article discusses a similar effect where the average wealth of US states is distorted by the super-rich. Smurrayinchester 12:09, 6 October 2017 (UTC)

• Don't know the name, but this is used to show the importance of using median incomes instead of average incomes. If you have a billionaire in a room with a thousand homeless men, their average income makes them millionaires, but saying "the room contains a thousand people, who, on average, are millionaires", is highly misleading. Yacht salesmen would be advised to look elsewhere. The median income correctly shows that most people in the room are dirt poor. StuRat (talk) 14:21, 6 October 2017 (UTC)

This effect might work out to the benefit of Paddock's victims, given his supposedly high net worth, as long as they take Hamlet's advice on the lawyers. μηδείς (talk) 19:32, 6 October 2017 (UTC)

• In statistics it is known as the outlier problem. Looie496 (talk) 13:17, 7 October 2017 (UTC)

• Not sure if that's quite right. The problem with incomes is they do not follow a bell curve, but are extremely lopsided.Thus, any statistical methods based on even distributions, like averages, don't apply to incomes. StuRat (talk) 04:00, 8 October 2017 (UTC)

An actual reference:

• "When Bill Gates Walks into a Bar". Introductory Statistics. 4 September 2011. — 2606:A000:4C0C:E200:CCE8:62C2:FF45:AE7B (talk) 05:46, 8 October 2017 (UTC)

Skin moisturizer as universal solvent ?

The first 4 ingredients in my skin moisturizer are water, mineral oil, stearic acid, and cetyl alcohol. So, it should dissolve substances which are water-soluble, oil-soluble, acid-soluble, and alcohol-soluble, right ? Is there some reason this is an important attribute in a skin moisturizer, or is this just a coincidence ? StuRat (talk) 14:29, 6 October 2017 (UTC)

Err yes & no. These are just the ingredients for making a Cream (pharmaceutical) which can be washed off. If you have a liquidizer in the kitchen you can make your own – and even eat what's left over. The important omega 3 fatty acids are left out of commercial products as they go rancid quickly and start to smell off. Aspro (talk) 15:37, 6 October 2017 (UTC)

That article says that water and oil are essential ingredients, and certainly for a moisturizer the goal is to add water to the skin, and oil is needed to hold it in and prevent immediate evaporation. That article also says an emulsifier and thickening agent are needed. Do the acid and alcohol serve those purposes ? If not, what do they do ? StuRat (talk) 16:38, 6 October 2017 (UTC)

From the stearic acid article: its primary use is as a "surfactant and softening agent" SemanticMantis (talk) 17:33, 6 October 2017 (UTC)

As I understand it oil & water are necessary to make a cream rather than a greasy ointment. The 'goal' of the moisturizer which one buys, is to generate profits for the share holders of the company. Any water can only affect the upper lays of the skin File:Skinlayers.png; like if one stays in the bath too long and ones fingers turn white and fingerprints expand, unlike bathing in sea water. No moisturizer on Earth will reach down to the lower layer where wrinkles form. Proprietary products use emulsifiers in order to combine oil & water (like egg yolks are used to combine the fat of dairy cream to make ice-cream and mayonnaise etc). See a dermatologist, for to find out what skin-care (note: I did not say treatment)suits your skin. If he says you have very thick skin – just point out to him, that as a WP editor -it is a necessity ;-) Aspro (talk) 17:54, 6 October 2017 (UTC)

I'm not looking for any medical advice, I only use skin moisturizer on my dry feet. Just wondered why it seems important for a it to be able to dissolve everything. StuRat (talk) 22:11, 6 October 2017 (UTC)

As an aside: Do you wear 'real' leather shoes and sandals? They (I assume) made the skin of my feet very thick around the edged of the heal. Assume it was the chromium tanning compounds leeching out and tanning my skin, stopping it flaking of in the normal way until they cracked and became sore. Found that with no leather no problem. Spanish leather riding boot etc' from Argentina don't seem to cause this effect. Maybe this is due to a different tanning process but anyway this all anecdotal. Aspro (talk) 20:51, 7 October 2017 (UTC)

No leather footwear, no. My issue is a poorly insulated home which therefore has dry air in winter, causing my lips and feet to dry out. This results in chapped lips and cracked skin on the bottom of my feet. I've tried humidifying the air, but it just condenses on the poorly insulated walls and windows and grows mold. Lip balm on my lips and skin moisturizer on the feet seem to solve the problem. StuRat (talk) 01:00, 8 October 2017 (UTC)

I know I shouldn't give medical advice and all that, so don't take it that way, but I'm inclined to mention that after having resorted to various not very effective though not entirely useless tactics like slathering the cracks in neosporin or trimming them down with a steak knife, I became convinced that when humidity is low enough there is no good way to avoid resorting to socks to hold the moisture in, at least for part of the day/night. Chapped lips are something I'm inclined to blame on anything but humidity; it never hurts to ensure riboflavin intake is up to standards. Wnt (talk) 13:42, 8 October 2017 (UTC)

I only get chronic chapped lips in low humidity, so I'm sure that's the problem, although salty food does seem to have the ability to suck the water out of my lips, too. The "dehydration" item listed isn't entirely wrong, as the lips are dehydrated, but not my body as a whole. Skin moisturizer doesn't entirely fix the dry skin on my feet, but does keep it from becoming severe. I'm sure applying it more often would solve the problem, but the issue is that I can only apply it before going to bed, as otherwise it would get all over my socks, shoes, etc., and make a mess (it does get on my sheets, but I can live with that). StuRat (talk) 16:57, 8 October 2017 (UTC)

To be clear, "acid-soluble" isn't really a thing. The long hydrophobic regions of stearic acid and cetyl alcohol help make them useful as emulsifiers. So you have water and oil (mineral oil, so don't eat it) kept in some kind of creamy suspension. Either water or oil can make skin feel wetter, and together they allow a broader range of hydrophilic and hydrophobic compounds to be dissolved in the cream.

In concept, a chemical put on the skin can work its way all the way down to the bone (hydrofluoric acid) so there is certainly nothing innately impossible about making an effective wrinkle cream. (If you happen to invent one, do tell us...) Wnt (talk) 12:09, 7 October 2017 (UTC)

Cure for wrinkles: Gain weight as they would form, to fill the wrinkles in with fat. (The wrinkles would eventually show anyway, but hopefully you will die from obesity before this happens.) StuRat (talk) 03:13, 8 October 2017 (UTC)

See also here. Count Iblis (talk) 03:00, 8 October 2017 (UTC)

Conductive fingernail decoration strip?

Is the metallic form of this nail strip (for decorating fingernails) liable to be conductive or is that a stupid thing to hope? I find myself in need of a conductive material that is adhesive, very narrow (~ 1mm) and aesthetically pleasing/decorative and it would be great if this was, even if the resistance is high for a conductor. --185.216.49.78 (talk) 17:01, 6 October 2017 (UTC)

Have you tried the fingernail tips for touch-screens? 209.149.113.5 (talk) 17:16, 6 October 2017 (UTC)

They also make gloves with those built in. I own a pair. StuRat (talk) 17:20, 6 October 2017 (UTC)

Very high impedance. Too high to power LEDs etc. Andy Dingley (talk) 17:24, 6 October 2017 (UTC)

• No, it's a plastic (often polyester) with an aluminium metallisation deposited onto it. As the metallisation is so thin, resistance is high.

You might find conductive thread to be more useful. Also kitchen aluminium foil can be used like this, so long as you glue it down. I usually stick it to double sided tape, with the backing tape still in place, then guillotine that into narrow strips. Copper is better than aluminium for some tasks, as the oxide layer is less troublesome. Andy Dingley (talk) 17:24, 6 October 2017 (UTC)

It's not impossible that it's conductive enough for your purpose. But I wouldn't bet on it. I suppose for 0.99 you don't have much to lose, except your time, but I think you'll be frustrated.

Alternatives are conductive ink, copper tape, or conductive thread.

Good luck with your project. ApLundell (talk) 18:01, 6 October 2017 (UTC)

Carbon fibre is good for this though hard to find. I was given threads from a place selling fibreglass etc. for boat repairs.Polypipe Wrangler (talk) 23:14, 6 October 2017 (UTC)

Salmon

What would happen if a person ate only Salmon every day? Could they survive on that and for how long? — Preceding unsigned comment added by 2408:802A:9700:5083:A0A4:B4BE:DED0:D63F (talk) 18:15, 6 October 2017 (UTC)

Till they run out of salmon? ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:44, 6 October 2017 (UTC)

• Conducting such an experiment would be unethical, and you haven't even told us if they are drinking water. See dehydration and ketoacidosis and ask us if you have a question answerable by references, not guesses. μηδείς (talk) 18:53, 6 October 2017 (UTC)

• Salmon seems quite low in many common vitamins, and in manganese and calcium: [5]. Scurvy and rickets are two possibilities. StuRat (talk) 23:47, 6 October 2017 (UTC)

I do not believe an exclusive salmon died would result in scurvy. Salmon has indeed vitamin C.Hofhof (talk) 10:54, 7 October 2017 (UTC)

My source (linked above) says it's not a significant source of vitamin C. Do you have another which contradicts this ? StuRat (talk) 00:54, 8 October 2017 (UTC)

• Another concern could be heavy metal accumulation (i.e. mercury) which is in higher quantity in large fish and in aquaculture-grown fish. —PaleoNeonate – 06:05, 7 October 2017 (UTC)

Wasn't there another recent speculative question about what would happen if someone tried to live on one specific food? And what was done with it, if anything? ←Baseball Bugs ^{What's up, Doc?} carrots→ 06:22, 7 October 2017 (UTC)

The question was closed too soon. Articles like rabbit starvation, No-carbohydrate diet or Inuit diet are about a similar issue. It's a fine question to me to ask what would happen if a human doesn't get enough of this or that nutrient.Hofhof (talk) 10:54, 7 October 2017 (UTC)

It was written by a drive-by, so it's unlikely he would even know if it was deleted. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:12, 7 October 2017 (UTC)

Those human-looking robots

You know each year they have those AI things where people make robots that are like people? Last I saw, they just stare off into space but talk like people. Can they now detect eyes and make eye contact and follow your eyes around? That would be well-spooky. Anna Frodesiak (talk) 23:59, 6 October 2017 (UTC)

This is nearly ten years ago https://www.youtube.com/watch?feature=player_embedded&v=hCsEFaInYlQ

For serious research, look at 'Kismet' at MIT Andy Dingley (talk) 00:07, 7 October 2017 (UTC)

Darn. YouTube is blocked in China. :( Would that have show the eyes thing? Anna Frodesiak (talk) 00:16, 7 October 2017 (UTC)

http://jarkman.co.uk/catalog/robots/theeyestheeyes.htm

http://www.jarkman.co.uk/catalog/robots/giantstaringeye.htm

Andy Dingley (talk) 00:43, 7 October 2017 (UTC)

That's a good start. Anna Frodesiak (talk) 00:56, 7 October 2017 (UTC)

This certainly is doable. We have other technologies that tracks eye movements to determine what the user wants. See eye tracking. The more subtle part would be in getting it to know when not to track eyes. For example, if I hand you a file and say "Here's the Johnson report" and you keep looking at my eyes instead of the report, I'd think there was something wrong with you. And then there's people on the autism spectrum, who often don't like people staring them in the eyes. This would upset them, especially if it wouldn't stop, when asked to do so. StuRat (talk) 00:25, 7 October 2017 (UTC)

That makes sense. Maybe it could track the nearest person, or the one emitting the most sound (the one talking). And that "Here's the Johnson report" thing reminds me of someone. Maybe he's a robot. I'm going to pour water on him to find out. :) Anna Frodesiak (talk) 00:31, 7 October 2017 (UTC)

Good thinking. That will also work if he's the Wicked Witch of the West, in disguise. :-) StuRat (talk) 00:36, 7 October 2017 (UTC)

Or one of those aliens from Signs (film). In fact, I think we should hire a hit man with a Super Soaker (we really do have an article on everything, don't we?) to hose down the top management of the WMF and see if they melt. You can't be too careful. --Guy Macon (talk) 01:24, 7 October 2017 (UTC)

Yes, water-soluble evil aliens without the sense to wear raincoats, on a planet where it rains regularly, really gave me a good laugh. StuRat (talk) 01:45, 7 October 2017 (UTC)

There could be multiple people talking. Also, whether they are looking at you should figure into whether you look at them, and also how well you know them, should. Then there are some cultures where servants aren't supposed to look their "masters" in the eyes, which would be important to know, if those robots are to be servants. StuRat (talk) 00:39, 7 October 2017 (UTC)

Well, for now, if it just stared at the nearest/loudest that would be pretty impressive, I think. Anna Frodesiak (talk) 00:55, 7 October 2017 (UTC)

Not just the loudest, that would mean always looking at Trump. :-) StuRat (talk) 01:49, 7 October 2017 (UTC)

Robots that Show Emotion is a relevant TED talk, as are the others on this play list [6].--Wikimedes (talk) 03:21, 8 October 2017 (UTC)

October 7

Are pumice stones a rational response to a callus?

I have a question that's only technically a medical question and I hope that you will indulge me on the basis that a) it's perhaps the least threatening of all medical anythings in the history of medicine and b) I resolved mine over a decade ago. When I was about 18-19, I somehow got a callus on my foot and when I asked my doctor about it, he said I should use a pumice stone on it. I complied for a while but it was uncomfortable and I just couldn't make sense of the advice. Given that a callus is the body's response to damage to the skin, how the hell is continually damaging the skin with a pumice stone an appropriate solution? In the end I over-ruled that stupid advice and left the callus alone and sure enough, in the absence of damaging stimuli, it went away. I just want to know whether the doctor's advice had any basis in sense or logic and have only just gotten around to asking. --185.216.49.78 (talk) 06:58, 7 October 2017 (UTC)

I don't know, but I just want to congratulate you on correctly spelling the noun as callus; so many people get it wrong. This is a regular paradigm: callus/callous, mucus/mucous, phosphorus/phosphorous — in each case, the version with -us is a noun; the version with -ous, an adjective. --Trovatore (talk) 07:03, 7 October 2017 (UTC)

As you implied, we can't (and won't) provide medical advice. We can link to articles such as callus and sources such as:

• "Calluses and Corns: Using Pumice Stones-Topic Overview". WebMD. WebMD does not provide medical advice, diagnosis or treatment.

—2606:A000:4C0C:E200:6130:AA57:396F:78BA (talk) 07:10, 7 October 2017 (UTC)

I believe the idea is that, after the stimulus that caused the callus to grow is gone, the callus won't disappear on it's own, at least not quickly, so abrading it off can speed up the process. Since the pumice stone is only used on dead skin, it's not supposed to damage the living part of the skin, so shouldn't cause more to grow. But if you do continue to damage the living part, say by walking barefoot on rough ground, then, yes, I would expect the callus to continually regrow. Incidentally, this is just a form of exfoliation, but with a very thick layer of dead skin, rather than the thin layer of dead skin on the face. Calluses that get too thick can provide fertile ground for plantar warts, crack and cause more serious problems, therefore keeping them under control is important, so that it doesn't become a medical problem. (I use a pumice stone on my feet after taking a bath, when the skin is softer and easier to remove.) StuRat (talk) 21:18, 7 October 2017 (UTC)

Are you removing calluses, or merely dead skin? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:01, 7 October 2017 (UTC)

Calluses are composed of dead skin, so yes to both. StuRat (talk) 22:07, 7 October 2017 (UTC)

If it's dead skin, I don't see why it would be a problem. Pedicurists do it all the time. My own doctor suggested it too. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:11, 7 October 2017 (UTC)

In some cases, calluses are helpful. Of course, the alternative is just to wear proper gear to offer the same protection as calluses, such as padded shoes or leather gloves. StuRat (talk) 23:10, 7 October 2017 (UTC)

I recall Pete Rose once talking about spring training and "getting the calluses going", as they would have faded during the off-season. The calluses enabled a player to improve his grip and were a better alternative than blisters. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:16, 8 October 2017 (UTC)

Yes, but batting gloves would be an even better option. StuRat (talk) 00:51, 8 October 2017 (UTC)

Except you can't feel the wood directly. But batting gloves (originally just golf gloves) were just starting to be used in Rose's day. They're in wide usage now. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:24, 8 October 2017 (UTC)

A good set of batting gloves should give you a better feel for the bat than thick calluses would allow. StuRat (talk) 03:56, 8 October 2017 (UTC)

How many more base hits would Rose have gotten if he had been an early-adopter of batting glvoes? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:08, 8 October 2017 (UTC)

Don't know, but I'm sure he would have taken bets on it. :-) StuRat (talk) 04:14, 8 October 2017 (UTC)

I googled the subject, and there are certainly a lot of products out there. One item (sorry, I failed to grab the link) warned against overuse of pumice... while promoting their own alternative product. It's fair to suppose that overuse of pumice could be counterproductive. But if you've got personal concerns, you should consult your physician. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:10, 8 October 2017 (UTC)

• WE DINNA GIVE MEDICAL ADVICE, but you might look at callus and pumice and you might even better see a podiater. Mine says my foot calluses need regular treatment and have a specific cause, but that's between him and me, and not an WP:RS. μηδείς (talk) 22:55, 8 October 2017 (UTC)

Electric powering a vehicle through induction

Could vehicles - real or bumper cars - get their power from the road (floor) through induction? In the same way that a cell-phone gets loaded on a charge pad? Would that be less effective than getting power from electric wires strung above (as streetcars do)? --Hofhof (talk) 10:50, 7 October 2017 (UTC)

Linking relevant articles: Inductive charging and Conductive wireless charging.--B8-tome (talk) 12:32, 7 October 2017 (UTC)

Due to the power requirements and the ground clearance needed, and having to place the charging coils under every place cars could drive, that doesn't sound practical, to me. You'd need too high of a field strength, which might cause other problems (like things bursting into flames ?). However, it might be possible when parked, especially if the charger could be raised up closer to the car after parking. StuRat (talk) 22:11, 7 October 2017 (UTC)

For electric vehicles, buses, trains, MAGLEV, etc. resonant inductive coupling shows promise. 2606:A000:4C0C:E200:1DF7:C3BD:258E:E025 (talk) 22:19, 7 October 2017 (UTC)

A Nissan Leaf or BMW i3 goes about 80 miles with a 20 kWh battery, which costs perhaps $7000. If you had a $1000 battery you could go perhaps 10 miles. This battery size would easily bridge most gaps in your inductive power system. Since you could recharge while driving, you solve the biggest problem with BEVs, which is the time it takes to recharge. However, the infrastructure for ubiquitous inductive charging would be prohibitively expensive. -Arch dude (talk) 14:33, 8 October 2017 (UTC)

Electrical charging of a car tends to be really slow, taking hours, so just driving over a small patch won't recharge the vehicle. This is why I say you'd need to park over it, for this charging method to be practical. Hopefully parking over it at night would give you enough charge to get to work, and if there's another charging station there, you could charge up while you work and have enough to get back home. For vehicles which stick to one route and lane, like buses, electrical induction charging while running may be somewhat more practical. It may not charge at the rate the electricity is used, but if it can extend the range to get the bus back to it's parking spot at night, where it can fully recharge, that would be good enough. StuRat (talk) 15:59, 8 October 2017 (UTC)

"Chemtrails"

How can I convincingly prove to others that so-called "chemtrails" are only jet exhaust? I know I can't prove anything directly to the conspiratards themselves because they're too stupid to look at other evidence besides their own, but how can I prove this to gullible people who may be deceived by the conspiracy theories? 2601:646:8E01:7E0B:0:0:0:EA04 (talk) 12:08, 7 October 2017 (UTC)

Chemtrails are only jet exhaust. They are also a sinister geoengineering conspiracy looking to sacrifice 1000-4000 lives a year to hold back global warming by six months and make air flights cheaper. There is actually no contradiction... [7] Wnt (talk) 12:13, 7 October 2017 (UTC)

Your geoengineering link is a disambiguation page. Which one were you meaning to link to? CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 13:09, 7 October 2017 (UTC)

Presumably: Climate engineering 2606:A000:4C0C:E200:1DF7:C3BD:258E:E025 (talk) 20:38, 7 October 2017 (UTC)

You can't really fight a completely irrational view with rational arguments. However, this is a good resource explaining how the conspiracy came to life: [8]. B8-tome (talk) 12:23, 7 October 2017 (UTC)

"Reasoning will never make a Man correct an ill Opinion, which by Reasoning he never acquired". The answer is that people who believe that are lost as humans, and should be written off. Trying to correct them is just throwing good money after bad. Get new friends.--Jayron32 20:49, 7 October 2017 (UTC)

This excellent summary [9] was in the Washington Post a few days ago. The comments section will provide some sense of how difficult it is to convince people that the notion is nonsense. Acroterion (talk) 22:08, 7 October 2017 (UTC)

@Acroterion: That article is remarkable in its ability to mislead. Oh, most of what they say is true - the planes nucleate clouds, and the only thing being released is burnt fuel. That said... conspiracy theorists looking for giant chemical tanks in the plane should look for fuel tanks, which fit the bill, and disperse their contents freely. [10] emphasizes that you can see differences in airplane contrails depending on a chemical present, namely sulfur dioxide. That right there is the heart of the "chemtrail" observation - people look up and they see some planes make funny looking clouds that don't seem like what they're used to. And the reason is because the fuel, which Washington Post tries to pass off as just "kerosene", can be up to 3000 ppm sulfur - that is to say, 0.3% by weight. If a 747 burns 36,000 gallons] in a 10-hour flight, maybe 250,000 pounds, that has 750 pounds of sulfur in it. If the plane had a 750-pound tank of molten sulfur in the back that it was visibly spraying over the course of each trip, people would say that confirmed the chemtrail conspiracy theory. Furthermore, as described here, the geoengineering goal of opposing climate change does factor in to policy discussions of whether the sulfur can be eliminated. So the Washington Post is being no more honest than the chemtrail conspiracy people here, and possibly less. Wnt (talk) 17:00, 8 October 2017 (UTC)

And anybody who's followed a Honda with a bad catalytic converter up a steep hill can tell that it's spraying sulfuric acid. And it's burning "just gasoline." So yes, reducing sulfur in fossil fuels is an issue for *all* petroleum fuels, as it was for diesel, notably high in sulfur, when it had to be reduced to make urea additives work (we'll pass over VW's deception for now - I had one of their diesels that they bought back). The difference between "sour" and "sweet" oils is central to petroleum chemistry and the economics of fuel products. But it's not new. Kerosene burned in airplanes is (I think) the same as it was in 1955, long before geoengineering was brought up as a solution to climate change. There are just more planes burning the same stuff they always have at 35,000 feet, completely driven by fuel price. I'd be interested in a comparison of sulfur content in jet fuel over time - has it been reduced?

In any case, the chemtrails folks are unconcerned with sulfur, they're looking for barium and other things that are supposed to make fallen snow look funny. Sulfur? Pah, everybody knows about that, they're looking for that special stuff that needs a special tank. They've got pictures of the tanks and everything. Acroterion (talk) 17:25, 8 October 2017 (UTC)

Something has changed with jet fuel or engine efficiency, because when I watched jets taking off in the 1960s, they left a trail of black smoke behind each engine, and I don't see that now. An example of a Boeing 707: [11]. StuRat (talk) 17:31, 8 October 2017 (UTC)

The engines have changed significantly - the JT3C turbojet engines on 707s were notoriously smoky, as were their counterparts on jet fighters. KC-135s and B-52s using water injection on takeoff left a blanket of black smoke, and the few that still exist with those engines continue to do so. Russian jet engines have a reputation for smokiness too, but most turbofan engines produce little smoke. Early F-4 Phantom General Electric J79s were smoky to the point of being a combat liability, something mentioned in our article.Acroterion (talk) 19:44, 8 October 2017 (UTC)

You might mention cloud seeding, which is related. In both cases, if you seed dry air, nothing much happens, but if the relative humidity is high, it causes water to condense and form clouds. Do they not believe in cloud seeding ? StuRat (talk) 22:26, 7 October 2017 (UTC)

Well as our article says, plenty of scientists are unsure cloud seeding actually generally does much based on the available evidence albeit generally measured on the success in increasing precipitation/rain. So if flat earthers feel the same they may actually be right for a change. (There is some evidence of possible effects on cloud structure and size and also in converting supercooled liquid water to ice particles.) Nil Einne (talk) 16:46, 8 October 2017 (UTC)

(ec) It doesn't do much in terms of increasing overall rainfall, no, because it doesn't create water out of nothing. But what it can do is cause it to rain slightly sooner than it would have, otherwise. As our article states: "Cloud seeding has been shown to be effective in altering cloud structure and size and in converting supercooled liquid water to ice particles. The amount of precipitation due to seeding is difficult to quantify. There is statistical evidence for seasonal precipitation increases of about 10 percent with winter seeding." StuRat (talk) 16:48, 8 October 2017 (UTC)

You first statement is not supported by our article, and since you provided no other source, it's supported by nothing. The closest is the winter thing, but even if it's true, that's a different claim. It's not clear if this is happening sooner, or you're making it rain elsewhere or what. I note the winter thing is from 1998. Meanwhile you've missed

A 2010 Tel Aviv University study claimed that the common practice of cloud seeding to improve or induce rainfall, with materials such as silver iodide and frozen carbon dioxide, seems to have little if any impact on the amount of precipitation

(emphasis added). Nil Einne (talk) 16:58, 8 October 2017 (UTC)

My first statement was "It doesn't do much in terms of increasing overall rainfall, no, because it doesn't create water out of nothing.". Are you saying it does create water out of nothing ? The part about not increasing overall rainfall much agrees with what you said and with the article. I didn't miss that bit, I said I agreed with it.

I'm guessing that you meant my second statement is unsupported by the source. Fair enough, here's one that does support it: "This means some areas that would not have received rain often do as a result of seeding. By seeding developing clouds before they start to produce precipitation, the precipitation process is accelerated and rain falls sooner, and from smaller clouds than it would naturally. Some redistribution of rainfall can occur within the scope of the storm itself, with computer models suggesting that regions of very intense precipitation may be slightly reduced while the total storm rain volume is increased." [12].

You seem to be missing that increasing overall rainfall substantially and bringing on rainfall slightly sooner, thus altering the distribution, are entirely different things. Cloud seeding only does the later, but that itself can be valuable, in certain circumstances. StuRat (talk) 17:01, 8 October 2017 (UTC)

I mean the second statement, sorry for the confusion. But otherwise I'm not misssing anything. "Bringing on rainfall slightly sooner" is by definition inducing rainfall which the quoted text explicitly said there was no evidence for. To be fair, I assumed this statement was supported by the source but it's not directly so I removed the wording.

But if you read the paper [13] it's clear this is a fairly complicated analysis. While they were primarily trying to determine if there was an increase in rainfall, they did look at different areas and as I understand it, didn't find any increase in any area over the others. (Of course part of the analysis was comparing seeded areas from unseeded ones.) Also I'm not sure what you mean by "sooner" here, but as I understand the paper, their assumption was the seeding would increase rain on the day of seeding (although they did have a problem that most of the days were seeded) meaning I think if it rained on the seeded day when it would have otherwise rained the next day, they may have detected this. (I say may mostly because the large number of seeded days combined with the difficulty in teasing out any signal means I'm far from certain this is the case.)

This is a single paper, so isn't great evidence. But your evidence by comparison is far worse, a brochure product by a local government trying to justify their cloud seeding efforts, who's only refs are the position statement of the Weather Modification Association and a MSc thesis? I wrote the below before I read you response, but your poor evidence gives it greater emphasis.

Of course the wider point which seems clear from our article is what the effects, if any, from cloud seeding are still largely unclear despite the practice being fairly wide spread. There appear to be some limited local effects in certain select circumstances although even in these cases, the evidence is often limited. (Notably as is often the case, given the strong commercial interest it's important to differentiate between actual published peer reviewed research, and claims made by 'experts' or those with a COI which aren't back up by peer reviewed research.) A lot of the governmental interest i.e. those most likely to be able to afford (and who probably should if they're going to spend significant amounts of money) to fund research to determine if what they're doing is achieving anything, is coming from Asia (including West Asia) and these countries are only just starting to get into significant scientific output. These efforts will of course largely be aim at widescale effects, given the costs involved demostrating that you may have had an effect on a few clouds is something which is always likely to be difficult getting funding for.

If you have any actual good evidence that Cloud seeding only does the later (let's ignore the only part), please provide it. I strongly suspect you do not because there simply is none. That's why people who surely now a lot more about this than you or I say things like

The only probable place where cloud seeding could be successful, Alpert says, is when seeding is performed on orographic clouds, which develop over mountains and have a short lifespan. In this type of cloud, seeding could serve to accelerate the formation of precipitation.

As I said, there is some limited evidence of effects in certain select circumstances. That's quite different from what you're claiming namely that cloud seeding is generally successful in "bringing on rainfall slightly sooner", or "altering the distribution". That's why plenty of people are unconvinced that China's cloud seeding efforts to try and improve the Beijing Olympics Games actually did much. Note that this isn't to say it doesn't do so, simply that our evidence for this is generally fairly or very weak and if you're going to make the claims here on the RD, you should either show that the evidence isn't weak, or make it clear the evidence is weak.

P.S. In case it's still not clear, by "good evidence" I mean peer reviewed published research, not claims made by governments to justify their efforts, nor statements made by those involved in weather modifications efforts. I'd accept publications from recognised scientified bodies like the National Research Council cited in our article as well.

Nil Einne (talk) 18:05, 8 October 2017 (UTC)

P.P.S. A point you seem to be missing, at least to my reading, is that altering the distribution of rain is often a key claim and a key point of dispute. Often goverments or whoever is paying for the seeding would be quite happy with simply altering the distribution of rain, since in plenty of cases, e.g. I'm fairly sure the Israel case is one example here, the governments want it to rain in certain areas and don't care if it rains in other areas. (In select circumstances they want to avoid rain in certain areas.) This can actually lead to disputes, when there's another party (e.g. different government) who suggest that the first party is "stealing" their rain. Yet there's generally fairly strong dispute that even these are actually achieving what's being claimed. And the boundary between "increasing overall rain" and "altering the distribution" isn't as clear as you seem to be suggesting. Making it rain sooner is perhaps less commonly a claim made, but still as the Beijing and Texas local government source demonstrate, this claim is also sometimes made, and frequently disputed. Nil Einne (talk) 18:16, 8 October 2017 (UTC)

"As I said, there is some limited evidence of effects in certain select circumstances." That "certain specific circumstances" part is exactly what I said. Specifically, you need high enough relative humidity for water droplets to form from seeding. But, getting away from this specific issue, was it really necessary for you to argue with every detail of my responses, in a Q that, after all, isn't even about cloud seeding ? This Q is about "chemtrails", and I only mentioned cloud seeding in passing, so it seems rather a waste of time for both of us to look up sources about a tangent like this. Now, for proper irony, I suppose we can spend several more days looking up my usage of the word "tangent" (and then "irony") here, if you feel that's important, too. :-) StuRat (talk) 19:59, 8 October 2017 (UTC)

Why not re-attach the kidney?

I watched an episode of The Good Doctor. In that episode, there was a woman with a tumor. It was determined that it was impossible to remove the tumor because a (healthy) kidney was in the way. In the end, the decision was to remove the kidney to be able to access and remove the tumor, thereby saving the woman's life. The dilemma was whether or not to remove a healthy kidney. It was healthy (and healthy kidneys can be donated to other people) and there would not be a risk of rejection since it was being returned to the person it came from. Other than for the purposes of drama for the TV show, what would the ethical dilemma be and why not reattach it? 76.71.156.197 (talk) 22:22, 7 October 2017 (UTC)

It's still an involved operation, with associated risks, and apparently they thought it was not worth the risk to go from one kidney to two, since one kidney seems perfectly adequate for most people. On the other hand, if going from zero to one kidney, it is worth the risk, in many cases, as lacking any functioning kidneys can be a death sentence (dialysis can keep them alive for a few years). StuRat (talk) 22:30, 7 October 2017 (UTC)

@ StuRat. More than "a few years". I knew someone who was on dialysis for about 30 years and there has been a case of 39 years. Both these cases were about 20 years ago, I suspect the technique is even more reliable today. Richard Avery (talk) 07:39, 8 October 2017 (UTC)

You're looking at the outliers, not the average. According to [14]: "Average life expectancy on dialysis is 5-10 years, however, many patients have lived well on dialysis for 20 or even 30 years." So, if you plan to have a long life, you really need at least one kidney (unless you're already old, then the risk of surgery outweighs the benefit). As far as improving survival, it seems to me we need to have a continuous wearable dialysis machine to do that, as allowing waste to accumulate for 2 or 3 days before removal will cause some minor damage, each time, until the cumulative damage kills the patient. StuRat (talk) 16:03, 8 October 2017 (UTC)

October 8

FLAT EARTHER speaks the truth

This is the best argument I heard from a flat earther where every statement he made (with the exception of "the earth is flat") is the literal truth.

“If you watch the trajectory of the Space Shuttle, it does not goes straight up, it always goes in a curve and out to sea (I think he meant the Atlantic Ocean). The point is, they actually goes horizontal. The Space Shuttle goes horizontal. It does not go any further up, it goes horizontal. This proves the earth is FLAT.” 110.22.20.252 (talk) 08:48, 8 October 2017 (UTC)

Have you got a query for the reference desk? Dmcq (talk) 11:08, 8 October 2017 (UTC)

Your title contradicts your post. 12.130.157.65 (talk) 11:11, 8 October 2017 (UTC).

To answer the implicit question: The Shuttle typically only goes to low Earth orbit, a few hundred km up. In order to stay up, it needs to reach a horizontal speed of roughly 7.8km/s (or about 28000km/h). Going into orbit is not primarily about going up, it's about going fast. --Stephan Schulz (talk) 14:07, 8 October 2017 (UTC)

Or in cartoon form, this. Henry^Flower 14:30, 8 October 2017 (UTC)

And if they acknowledge the existence of orbital spacecraft, how exactly do they propose it goes around a flat Earth ? Does it go over the "edge" at some point, fly past a bunch of tree roots hanging down, then over another edge and back to the top ? StuRat (talk) 16:14, 8 October 2017 (UTC)

I think they would think it actually follows a circular path over a part of the flat Earth and does not reach the edge. --69.159.60.147 (talk) 18:33, 8 October 2017 (UTC)

Then they would need to fire the engine continuously, to fight gravity, and would quickly run out of fuel. We have satellites which have been in orbit for decades, without refueling, and how about the Moon ? StuRat (talk) 19:42, 8 October 2017 (UTC)

Thusly:[15] Gråbergs Gråa Sång (talk) 18:52, 8 October 2017 (UTC)

I have to protest against that outrageously unscientific and misleading picture! As we know, it's turtles all the way down! --Stephan Schulz (talk) 19:52, 8 October 2017 (UTC)

The sun's orbit is so complex that one of the elephants has to cock its leg to allow the sun to continue on its orbit. Gråbergs Gråa Sång (talk) 20:42, 8 October 2017 (UTC)

I think my point is that EVEN IF FLAT EARTHERS speaks the truth, they draw the WRONG CONCLUSION. For example: They think that if the earth is a sphere then the space shuttle must goes straight up, the fact that the shuttle, goes up and then turns towards the horizontal direction must be a conspiracy to fool the public that the earth is sphere. They could not imagine why the shuttle does NOT GO STRAIGHT UP if the earth is a sphere, unless the shuttle may just hit the SUN or the MOON, after all the SUN and the MOON is actually very low in the sky (according to Flat Earth astronomy). 110.22.20.252 (talk) 06:35, 9 October 2017 (UTC)

The equations of dynamical systems in our physical theories

A dynamical system is basically a function that maps a point in time to a system's state; call this function $f:times\rightarrow states$. Sometimes, an equation places restrictions on the possible values of $f$. For example, Hamilton's equations in classical mechanics, Maxwell's equations in classical E&M, and the Schroedinger equation in quantum mechanics, all dictate that the state evolve in a certain way, and that you cannot have arbitrary $f$. Indeed, this is basically what makes a theory a theory. Our mainstream physical theories can be divided into the following, with corresponding equations:

Classical mechanics - Hamilton's equations

Classical E&M - Maxwell's equations

Quantum mechanics - Schroedinger equation

Special relativity - ??

General relativity - ??

Quantum field theory - ??

And maybe some theory of everything such as string theory - ??

My question comes from those question marks I have put above. I simply don't know what the equations are which govern the time evolution of the system for those theories. Can someone tell me?

Perhaps one complication is that the three theories I have filled out are nonrelativistic, whereas the remaining four are relativistic, and in relativity, the whole notion of "time" is unintuitive and perhaps not conducive to describing dynamical systems with equations like Hamilton's equations. However, one could still define an equation that describes the evolution of a system with respect to a particular observer... couldn't one? PeterPresent (talk) 12:27, 8 October 2017 (UTC)

Special relativity: the Lorentz transformation. General relativity: the Einstein field equations. Quantum field theory is based on the Schrödinger equation, except that it uses a far more complex state space and Hamiltonian than ordinary quantum mechanics. Looie496 (talk) 13:53, 8 October 2017 (UTC)

I hope you don't mind me tweaking some of your suggestions as well as filling out the blanks. In the examples you give, Maxwell's equations are the odd one out. Both Hamilton's and Schroedinger's equation(s) can be thought of as rules that allow you to derive differential equations for the time evolution of a system. They can arguably be seen as defining the theory, but cannot tell you anything about the dynamics of a given system without extra information: in both cases you need to know the Hamiltonian. For example, one classical mechanical Hamiltonian will correspond to a ball moving around ballistically under the influence of gravity, but there are infinitely more possibilities. Maxwell's equations are more specific than Hamilton's or Schroedinger's. They are more analogous to the specific differential equation which describes the ball than the master equations which could be taken to define the theories of classical mechanics or quantum mechanics. In fact, Maxwell's equations can be derived (if you posit the appropriate Hamiltonian) from a similar master equation for classical field theory. The Hamiltonian formulation of that is discussed a bit in: Hamiltonian field theory.

For special and general relativity (SR and GR), it is really just the same mechanism: you can use a variational principle to derive a differential equation governing the time evolution of the system. The conventional way to do this is to work in the Lagrangian formalism and simply ensure that your Lagrangian is symmetric under your new transformations. For SR, you end up with a very similar formalism to that used for classical mechanics called relativistic Lagrangian mechanics, while GR leads you to a (diffeomorphism covariant) type of classical field theory. Note that for GR, the equivalent of Maxwell's equations are the Einstein field equations, but that both of these are really just the Euler-Lagrange equations for their respective systems.

Quantum field theory is admittedly a bit more complicated, but at its heart it is just a blend of the classical field theory and quantum mechanics. As pointed out by Looie496, it has a Lagrangian density which governs the time evolution of states (for an example see e.g the Standard Model). Depending on what you're doing though, you might never work with a specific time evolution equation that needs to be solved (for example most calculations for the LHC are done via the S matrix formalism which only considers particles in the infinite past becoming different particles in the infinite future). However, you may be interested in reading about the effective action, which is a scarier QFT version of the familiar variational approach from the other theories. 92.18.79.227 (talk) 20:22, 8 October 2017 (UTC)

Thanks for your answers! So, the Euler-Lagrange equations could be seen as the "master" equation that governs the time evolution of systems in GR and more specific theories (classical mechanics, classical E&M, special relativity) and possibly QFT as well. One thing I've always been unsure about though is whether the theories in GR only describe the evolution of a system in an unchanging spacetime. Can the Einstein field equations be used to solve the two-body problem in general relativity, for example, where the evolution of the system both affects and is affected by the changing spacetime?

But perhaps a more important question is this: How do scientists derive these equations in the first place? For example, I have read the article Euler-Lagrange equation and it looks like a mathematical technique that relates to the physical world through the principle of least action. How did scientists derive this law, or our other equations describing the time evolution of physical systems? PeterPresent (talk) 00:36, 9 October 2017 (UTC)

Nose blindness

Apparently, "Nose blindness" is a real thing (not just a marketing gimmick). See: [16] & [17]. Per the latter, Pamela Dalton of the Monell Chemical Senses Center is a primary researcher on the subject. Is there another term for the phenomenon? The closest I could find on WP is Anosmia, and the general term, sensory adaptation. — 2606:A000:4C0C:E200:CCE8:62C2:FF45:AE7B (talk) 18:06, 8 October 2017 (UTC)

Hyposmia is a reduced ability to smell odors and might be a very early sign of Parkinson's disease, or rarely of Kallmann infertility syndrome and is arguably (no reference) among the health effects of smoking. Cultural Habituation plays a part; my only visit to India was a short stay downwind of Bombay whose scent(s) live on in memory. Blooteuth (talk) 21:35, 8 October 2017 (UTC)

I assume I suffer this. I cannot smell farts, flowers, fruit, or anything else besides burning materials. I had nasal polyps removed at age 18, and have lost at least 98% of my sense of smell. I can smell burning objects and human pheromones. I do so miss the lovely smell of gasoline! μηδείς (talk) 22:19, 8 October 2017 (UTC)

I believe the appropriate article is Olfactory fatigue; would a redirect be WP:OR? — 2606:A000:4C0C:E200:CCE8:62C2:FF45:AE7B (talk) 22:44, 8 October 2017 (UTC)

Thanks. I think that now that there is advertising attempting to popularize the phrase "nose blindness", a redirect should be added and the phrase should be mentioned in the article's lead section. --69.159.60.147 (talk) 03:26, 9 October 2017 (UTC)

Toothache becoming pulmonary problems

I ran across this quote from a non-medical book published in 1888:

A few weeks preceeding [sic] his death, he contracted a cold resulting in a violent toothache, at the time occasioning no alarm; but the disease extended rapidly to the lungs, causing congestion, from which he died, at the residence of Mr. James Smith, in Baltimore, Maryland, September 3, 1856, and was buried in Philadelphia.

What kind of disease could do this? I assume that a toothache can lead to life-threatening bacteremia, but how would this be related to pulmonary problems? Do we have to assume that the toothache and congestion merely co-occurred, and the non-medical observers incorrectly attributed all the symptoms to the same disease? Nyttend (talk) 21:44, 8 October 2017 (UTC)

My sister had strep throat and died of heart failure a week later. The Autopsy indicated cardiac lesions that would probably not have killed her, except that there is a history on my dad;s side (my cousin, two of his aunts) of women dying after a "cough." μηδείς (talk) 22:14, 8 October 2017 (UTC)

October 9

How much effect do humans have on tides, wind, Earth's rotation and the Moon's position?

How many millimeters less are the tides in some places because of anthropogenic things like tidal power plants? How many millimeters/seconds of arc late or early is the Earth's rotation and Moon's position because of tidal power plants, humans moving things around affecting the rotational inertia, melting ice faster and so on? How big is the biggest zone with average wind reduction ≥0.1kph or ≥1kph from windmills? Sagittarian Milky Way (talk) 00:06, 9 October 2017 (UTC)