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May 4

Newton trying to convince people that energy is physical

Hi all - is it true that Newton found it difficult to convince others that energy is physical, in the same way that people find it hard to think of information as physical? If so, can someone cite some references? Thanks Adambrowne666 (talk) 02:38, 4 May 2016 (UTC)

This is a bit philosophical. I'm not a student of Newton or anything, I did some university physics, but I'm not sure any physicist considers "energy" it self to be physical. In fact I find this is one of the biggest misconception held by most people; that energy IS a physical "thing", that you can have a jar full of "energy" or a ball of "energy" can fly through space, or that the human body has some "energy field", or that there is such a thing as "pure energy". Energy is a property of physical things or systems, it's not it self a physical "thing". Vespine (talk) 03:54, 4 May 2016 (UTC)

Unless of course you mean Mass–energy_equivalence then I take back all of the above, but Newton predates that by a few centuries. Vespine (talk) 03:55, 4 May 2016 (UTC)

Yeah, maybe I'm putting it wrong - what I mean is, I've heard that Newton had difficulty in getting people to think of energy as a thing - a property that can be discussed in the same way that weight is... Am I getting closer? Adambrowne666 (talk) 04:12, 4 May 2016 (UTC)

Riiight. Ok, i think I understand. I have not heard about it specifically related to Newton, are you perhaps thinking of Caloric theory? Vespine (talk) 05:20, 4 May 2016 (UTC)

Did Newton's even have a conception of energy? I'm not sure that he did. I thought that energy was largely developed as a concept in the 19th Century, in part because of heat–kinetic energy equivalence noted in the steam engine, and in part from Hamilton's reformulation of mechanics. — Preceding unsigned comment added by Star trooper man (talk • contribs) 10:18, 4 May 2016 (UTC)

"Earlier workers, including Newton and Voltaire, had all believed that "energy" (so far as they understood the concept at all) was not distinct from momentum and therefore proportional to velocity." From Conservation_of_energy#History. More good stuff in that section too. SemanticMantis (talk) 13:57, 4 May 2016 (UTC)

I would have thought that the problem was the reverse of that. Newton was an alchemist - and some of those guys (but evidently not Newton) believed in Phlogiston theory - where phlogiston is a physical substance (albeit with a negative mass!) that had properties somewhat similar to the modern concept of "energy". So I'd have expected Newton to have to work hard to demonstrate that energy was not a physical thing - but merely a measurement akin to "mass", "charge" or "temperature". SteveBaker (talk) 01:05, 5 May 2016 (UTC)

Take the idea that the sun warms the ocean and causes water to evaporate. Then some of that water falls upon high ground and forms a river which runs downhill and works a mill. which grinds corn. Today, we all understand that energy is being transferred from one form to another, but is conserved. If it is cold, less rain is formed, and less wheat is ground. This everyday notion of the conservation and transformation of energy is so common today that we forget that is was an alien concept before Newton. Philosophers assumed that different types of natural events had their own way of doing things, Celestial objects worked according to their own laws, very different those which were found on Earth. The vitalist forces which made life possible were set apart from those which determined the weather. The notion that energy permeates very different systems, and is conserved, that is, cannot be created or destroyed suddenly made a single calculus the measure of ALL things, and thus was, probably, the foundation of modern science. I presume that this is what is meant by the OP talking of energy being physical. Myles325a (talk) 05:21, 5 May 2016 (UTC)

Thanks for your answers, all - it's clearly a case of memory being a peeling wallpaper over the walls of the vast chamber of forgetting - still, it's good to have it cleared up Adambrowne666 (talk) 01:01, 6 May 2016 (UTC)

Why is a kidney dish so shaped?

The WP page for this: Kidney dish provides a few pictures, and notes that bowl" is a shallow basin with a kidney-shaped footprint". I immediately imagined that they must be equipped with some ambulatory prowess, and wondered if such were kept under lock and key when they were not being used. Perhaps, the mundane "base" might have sufficed. The article notes that the dish is shaped so it can be held against a curved surface such as a torso, and collect blood more efficiently than a dish with straight sides could. Fine. But I had long thought that some shapes for dishes render them more stable, and less inclined to tip over, and others are inherently unstable. The kidney dish, I had long-thought, was one of the former. Can anyone throw some light on this? I believe that dishes with circular bases are the most unstable. But have there been any experiments with dishes being pushed, jolted and tilted to see which shape is the most stable? Myles325a (talk) 07:28, 4 May 2016 (UTC)

AFAIK (which isn't a reliable source) the shape is indeed from that of blood-letting bowls, where the concave edge made them useful for catching the most blood (or whatever else is falling out of a patient). The rest is convention and the fact that even when a kidney-shaped bowl isn't useful for a particular task, it isn't a drawback and it allows them to stack with the other kidney-shaped bowls. Instrument trays though are rectangular, as they make better use of space on a small trolley.

I think the shape is based on the upper rim, not the base, and that stability doesn't enter into it. Stability is mostly about the steepness of the sides (shallow sides make a narrow base and that does reduce stability). Shallow sides also make for more splashback. Nursing 101 of course explains why not to try to catch vomit in any shallow dish-shaped bowl. Andy Dingley (talk) 10:32, 4 May 2016 (UTC)

Here is a circular bowl (with a circular base) that is very stable. http://www.academy.com/shop/pdp/ruffin-it-stainless-steel-dog-bowl-018946848p--1 It depends on more than just the footprint. 196.213.35.146 (talk) 10:36, 4 May 2016 (UTC)

OP Myles325a back live. Thanks number man, this lovely image is that of a dog bowl, where the rim curves inward, not straight up or outward, probably because that set up helps contain the food within the bowl as the dog wrestles with and devours it. Is this configuration more or less stable than bowls with rims which curve outwards, or is it all the same? I would opt for the former because, while the centre of gravity remains the same as with the inward-pointing rim, the outward-pointing rim is inherently more unstable. For example, the dog could suddenly press down on the outward rim tipping the bowl towards him. This cannot happen with the inward-pointing rim bowl. I would hazard a guess and say that while the centre of gravity’s position is important to stability, it is NOT the be all and end all of the matter. The inward-pointing rim bowl has its mass distributed over a smaller area, making it harder to upset. Myles325a (talk) 04:04, 5 May 2016 (UTC)

Any rigid body resting on a flat surface is in a stable state if its Center of mass lies over its base area. Round vases, bottles, dishes etc. with circular bases are not inherently unstable but vary in their critical tippling angles $A$ which measure how far they can be tipped to one side and still return to their upright position.

$A=arctan(r/h)$

where $r$ is radius of the base, $h$ is height of the center of mass. A tall bottle with a small base has small $A$ and is only weakly stable since a slight tilt will topple it; conversely a symmetrical solid Cone object that has large $r$ with small $h$ has large $A$ so it is difficult to topple. A kidney dish has largest $A$ (is least liable to topple) when it is empty because filling the dish raises $h$. The dish's resistance to toppling is least ($A$ is small) in the direction of its short dimension. The characteristic curvature in its long dimension makes almost no difference to its overall stability. AllBestFaith (talk) 12:01, 4 May 2016 (UTC)

OP Myles325a back live. Thanks, AllBestFaith, you have done more to address this quest ion than anyone else. Leaving aside the maths, it is obvious that (say) a vase with a circular base and with a low perimeter is more stable than one with the identical base but with a tall perimeter, as per your bottle example. Note that both vases have the same centre of gravity. Thus this thought experiment shows that centre of gravity is not the only feature influencing stability. But my query is not directly concerned with the matter of how rims affect stability, which has been settled by your answer, it is more concerned with how the layout of the base affects stability. So we could assume for all cases under consideration, the rim is straight up, and its height is derived as a function of the area of its base. (And of course, they are all made of the same material Myles325a (talk) 04:19, 5 May 2016 (UTC)

OP Myles325a – This just in. AllBestFaith, you note that “A kidney dish ...(is least liable to topple) when it is empty... Let me see if I have got this right. You would intuitively expect a full bottle to be more stable than an empty one, as its weight makes it harder to tip over. But then, a dish with a big base relative to its low perimeter might well be inherently unstable. Think of carrying a frying pan full of water. The greater the area of the pan’s base, the more likely it is that the water will begin to slosh about and spill. But these considerations are perhaps sidetracked by questions of fluid dynamics. If we put sand rather than water in the pan, it would be far more stable. Myles325a (talk) 04:35, 5 May 2016 (UTC)

A kidney dish has a flat bottom so shouldn't tip over because of instability. --TammyMoet (talk) 14:05, 4 May 2016 (UTC)

The answer to the question is this sentence in the article: "The shape of the dish allows it to be held against the patient's body to catch any falling fluids or debris." ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:15, 4 May 2016 (UTC)

I remember being in 6th grade or thereabouts and reading about medical and surgical practice. When I read about "kidney dishes" in the hospital I assumed it was designed for a surgeon to deposit an excised kidney in, and wondered if there were specific named dishes for each organ which might be removed. ("Nurse! Bring me a spleen dish, an appendix dish and a gall bladder dish!") Edison (talk) 16:03, 4 May 2016 (UTC)

Shocked doctor: "No, no nurse, I said Remove the patient's SPECTacles" AllBestFaith (talk) 22:54, 4 May 2016 (UTC)

I've always rather fancied getting some kidney dishes to serve kidneys in. Soup goes in a soup bowl, gravy in a gravy boat, so why shouldn't kidneys get their own dish? DuncanHill (talk) 22:59, 4 May 2016 (UTC)

What kind of dish are you going to use for the spotted dick, and will you put two appropriate vessels of Rocky Mountain oysters in a bag along side? DMacks (talk) 23:29, 4 May 2016 (UTC)

OP Myles325a rides again. Thanks, Edison; this is kinda a cross twixt an eggcorn and a mondegreen. I rem the Walrus and the Carpenter poem from “Through the Looking Glass”. A couple of lines from there go: “To talk of many things: / Of shoes--and ships--and sealing-wax--...For many years I thought it was “ceiling wax”, which I assumed was some special compound like fine plaster to coat the rosette around a pendulous light. It is pure felicity that a misconception like that should occur via Lewis’ work, which plays extensively with such constructions.

I think that I have nutted out a bit more of this problem. A circle is the most compact way of containing a given area. So it is the most unstable. If you take the same area (a hamburger patty) and spread it out (a sausage) it becomes more stable. The kidney dish is a more stable way of organizing the base area because it spreads the outer circumference of the dish. So a U is more stable than a O. And if we twisted one side of kidney dish to face the opposite direction, it would form an S, and that would be even more stable. If you do not think this is plausible, think of a circular base of a radius of (say) 10 centimeters. Now imagine taking that circular base and extruding it so it forms a long rectangle that is only a centimeter wide. Is not that shape very stable. Now imagine taking this long rectangle and making it into a loose spiral that has a radius much larger than the original circle. This kind of base would be very stable indeed. It becomes impossible to think of how it could be tipped over. Myles325a (talk) 05:26, 5 May 2016 (UTC)

And to top it off, we can fill in the needlessly unused spaces in that long spiral and make it a circle, so it is most stable of all. :) ... I have no idea, I really don't ... :) Wnt (talk) 21:06, 5 May 2016 (UTC)

Symbol & in Html

what is the html code to get this symbol &  ???--Ip80.123 (talk) 09:56, 4 May 2016 (UTC)

&. See more at &#Computing. PrimeHunter (talk) 10:25, 4 May 2016 (UTC)

Also, see ampersand, which is what the symbol is called. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:29, 4 May 2016 (UTC)

Recovering data from Iphone soaked in salt water

This question would apply to Iphones or other digital devices with memory chips which are recovered after being immersed in water or recovered from a wet environment. Two 14 year old boys went fishing in the Atlantic ocean in a small boat and were lost at sea. The boat was found months later and hundreds of miles away complete withe their celphone, which had been soaked in salt water. A news article said it might be impossible to recover any stored data such as videos, voice memos, notes, GPS locations, or numbers dialled, since it was claimed 'the entire phone had to be functioning" to recover data. It is said to be a "newer model" Iphone, and might have the same passcode issue as the terrorist iphone which the FBI had someone hack. My basic question is, why couldn't the Mobile DDR be unsoldered, cleaned, and downloaded to a backup storage, so there is no possibility of deleting the contents from too many attempts at the passcode, and then brute force attempts be made in cracking the passcode. If the cloned chip is erased after 10 attempts, reload the source data and try the next 10 sequential passcodes. This could easily be automated, and 10000 attempts should take way less than a day. Are there other chips which store data on an Iphone which make it different than any other Iphone of the same model fresh in the box? In other words, does the memory chip only function with its fellow chips from the original phone? Is a "recent model Iphone" passcode restricted to 4 digits, or can it be longer and more varied? How well sealed are present-day chips against ingress of water into the plastic encapsulation? I would expect there are many cases where someone wants to retrieve data from memory chips which have been immersed in saltwater, and there are reports of data recovery after "days" of immersion in saltwater. In this case it was "months." Are memory chips tested at all for maximum data survival while immersed? Edison (talk) 16:39, 4 May 2016 (UTC)

This and This imply it is not as simple as you make it out to be. --Jayron32 16:45, 4 May 2016 (UTC)

I didn't "make it out to be simple." I just asked why if was impossible even in principal.Is it possible to unsolder a chip from a circuitboard in an Iphone, if you have the training and tools? Having achieved that step, the question is whether the data on the chip can be transferred to another memory chip. Someone found a digital camera which had been dropped in the ocean 4 years earlier, and had no trouble recovering all the data, after a good cleaning. In criminal cases where a phone was buried or tossed into the bay, or if loved ones were drowned in a boat accident, small plane crash or hurricane, someone might be interested enough to pay someone to do even painstaking steps to recover data. The news story said that one would have to power up the original Iphone to recover the data, and I'm asking if that is correct. Is the Mobile DDR chip that much more fragile in saltwater than the camera chip which was downloaded after 4 years in the ocean? Edison (talk) 17:11, 4 May 2016 (UTC)

As I read this question, Edison is specifically asking about iPhone, rather than about a generic modern digital device at large. Per the publicly available iOS Security Guide, "Every iOS device has a dedicated AES 256 crypto engine built into the DMA path between the flash storage and main system memory, making file encryption highly efficient." Clearly, a highly-capable and well-trained, well-funded organization could have the equipment to carefully disassemble the hardware... but even if you were able to remove the nonvolatile storage hardware without damaging it - and if the hardware was undamaged by exposure to the natural elements - the contents are strongly encrypted. One would not be able to trivially decrypt the content, and even with a brute-force attack, it would be very difficult to recover any data. The nature of strong encryption implies that one would not even be able to locate the data that was securely encrypted: the user's protected data would be completely indistinguishable from empty space on the file-system unless you could break that encryption. Nimur (talk) 18:47, 4 May 2016 (UTC)

Beyond what Nimur has said, you seem to be confusing different things. As the article you linked to says Mobile DDR is a form Dynamic random-access memory i.e. Volatile memory. While there has been some observed Data remanence#Data in RAM in certain forms of DRAM [1] for minutes or hours, and longer if cooled, none of these are likely in the scenario you outlined or really most scenarios with a phone. Perhaps the only likely would be if the phone is still on and you think there's something useful in the RAM. However it's very risky since you risk damaging something and the the earlier link makes me wonder if you even have any hope of recovery (most phones now use mobile DDR derived from DDR3 or may be even DDR4 AFAIK).

In truth even if you could recover, the difficulty of access etc means it's going to be very rare anyone attempts to recover data from mobile DDR. Remember you have to do it quick before the data is no longer recoverable probably in a cooled environment.

Recovering data from the non volatile flash memory storage is a different matter. But as has been said by Nimur, recovering the data is of limited utility if you can't decrypt it. And depending on the design of the phone, decrypting it may be very difficult if all you have is the flash memory content and not whatever was in some other chip which may store part of the decryption system. You will have to bruteforce the whole key rather than simply the password, passphrase, PIN or whatever.

Nil Einne (talk) 19:59, 4 May 2016 (UTC)

So while it was recently proven it might not be "IMPOSSIBLE" to crack an iPhone's security features, it took, probably THE most well resourced intelligence agency in the world several months to get into one phone, for reasons of, literally, national security. We still have NO idea how they actually did it. For all we know it might have included a secret deal with apple, or even an apple "mole". It seems unlikely anyone would be in a similar position and willing to spend the same amount of resource to get some data from the phones of 2 people who were confirmed lost at sea. Vespine (talk) 01:46, 5 May 2016 (UTC)

The FBI isn't an intelligence agency. Also, they have stated publicly in broad terms how they got in; they bought an exploit from an Israeli cracking firm. Obviously it's up to whether you believe them, but the story is very plausible. There are dozens of these firms that specialize in finding exploits. Basically all software is buggy and full of undiscovered security holes. For instance, here's the latest massive security hole in widely used software, just revealed the other day. --71.110.8.102 (talk) 05:58, 5 May 2016 (UTC)

I'm not certain if precisely who they bought it from was ever revealed see e.g. [2] [3] [4]. However who they paid seems to be mostly beside the point. And Vespine's comment suggests some confusion about what the FBI actually did. As far as we know, all they seem to have done is gotten around the artificial time and trial limitations allowing them to keep trying PINs fairly quickly, which is what they wanted Apple to do for them [5] [6] [7] [8] [9]. This exploit is largely irrelevant to what's proposed by Edison namely simply removing the flash chip. I don't think we know precisely how it works, there was some very early speculation here [10] but what the FBI have since disclosed suggests there's no physical modification of the phone needed. Since the problem seems to be at least partially that it's likely some components are damaged, I guess you could move the flash and security chip to another phone of the exact same design if they were working fine. And this probably won't work partially because of software. In that case you may need an exploit similar to the San Bernadino case. But that's a lot of ifs. Nil Einne (talk) 09:34, 5 May 2016 (UTC)

BTW, I should perhaps clarify that I'm in agreement with Vespine's basic point namely that the cost involved means there's a fair chance no one is going to be willing to do it. I'm just saying that concentrating on the security aspect is likely missing the point. It's probably a factor in that it means having gone through all that efforts, there's a reduced chance of recovery and a risk of more costs. (Although realisticly even without the security aspect, it's still likely to be very difficult to predict if you'll get anything useful and how hard it'll be.) But it's also a long way before you even get there. Nil Einne (talk) 20:06, 6 May 2016 (UTC)

"71.110.8.102:The FBI isn't an intelligence agency.". The opening line of our FBI article: The Federal Bureau of Investigation (FBI) is the domestic intelligence and security service. I admit I have not researched in depth exactly how it was cracked, my point was: it was. Vespine (talk) 23:16, 5 May 2016 (UTC)

Cookies in a Tin - Nitrogen?

High-quality (sometimes imported) cookies (any language variant) are sometimes sold in a tin that is sealed with a plastic-like or cellophane-like sealing material, which is easily ripped off when opening the tin. I remember that, in the past, occasionally when such a container was opened, there was a slight hissing sound. That would have indicated that the tin had been evacuated and that the cookies were vacuum-packed to ensure freshness. (Is there a pun to vacuum-packing? How can nothing be packed in a tin? Well, the cookies are not nothing, just packed in nothing.) Sometimes these days there is no sound on breaking the seal, but the cookies are fresh several months after the tin was sold. Presumably the original reason for evacuating the tin was that oxygen can react with the cookies and cause them to become stale. If there is no sound on breaking the seal, that suggests that the tin wasn't evacuated. My question is: Are the cookies preserved by packing them in nitrogen or carbon dioxide? I can see that any reaction with carbon dioxide would be slower than with oxygen, and with nitrogen would be even slower. (While monatomic nitrogen is an extremely reactive gas, diatomic nitrogen is about as inactive as a gas can be that isn't truly an inert gas, because the dinitrogen triple bond is one of the strongest bonds known in chemistry. That is, those nitrogen atoms really "want" each other.) When a tin of cookies or other food is sealed, is nitrogen used to ensure freshness? Robert McClenon (talk) 16:49, 4 May 2016 (UTC)

This article looks interesting. As does This video. --Jayron32 16:52, 4 May 2016 (UTC)

These how it's made-type videos are like Qoyaanisqatsi, but without the moralism. Asmrulz (talk) 23:03, 4 May 2016 (UTC)

In fact, it is more important to keep out moisture and light - though an inert gas may be used in some cases (it rather depends on the type of biscuit). 81.132.106.10 (talk) 17:20, 4 May 2016 (UTC)

Jayron32 deliver good references as usual. Lets consider the question of whether a cookie tin could have a full vacuum inside. An old standard science experiment to demonstrate the pressure of the atmosphere, around 14 pounds per square inch, was to boil water in a 1 gallon metal can with a screw-top, made of steel of similar thickness to a cookie tin. Once the small amount of water in the bottom was boiling good, and the can was full of steam, the heat was shut off and the cap was screwed on. Immediately the can was crushed nearly flat, as the steam condensed and there was no pressure inside to counter the atmospheric pressure outside. The lamer experiment today uses an empty unsealed Coke can with stem inside which is crushed when inverted i a pan of cold water. But similar to your experience, I have purchased ground coffee in a plastic cylindrical container, with a metallized plastic seal on the top. When the plastic is punctured, air hisses INTO the can and the concavity of the seal is reduced. Maybe they ship it with some of the air removed, or with some of the air removed and nitrogen replacing it.Maybe the ground coffee resists the crushing of the container. I wouldn't expect cookies to resist can crushing at all. If the gas in it is nitrogen, though, I don't see the point of the reduced pressure. To save nitrogen? Edison (talk) 17:35, 4 May 2016 (UTC)

Stem? DuncanHill (talk) 23:02, 4 May 2016 (UTC)

Highly unlikely a tin could withstand full atmospheric pressure with a vacuum inside. The cookies would crumble because of the pressure changes too. But a small pressure differential may be created if the cookies are put in the tin at a high altitude or slightly warm. Water vapour present in the tin may be absorbed by the cookies, creating 1 kPa or so underpressure before the air in the tin is dry.

If any preservative gases were added to the tin it should be mentioned on the packaging. At least, in Europe it should be mentioned. Look for statements like "packaged under a protecting atmosphere" or whatever it is exactly in english or your language. Have a look at packaging gas and E number, in the range 938–949. PiusImpavidus (talk) 19:24, 4 May 2016 (UTC)

Yes, a hissing sound is associated with reduced pressure packing but inert gases can be used in combination. Where there is no hissing for cookies containers I hazard a guess that its argon and its E number may not appear. Being mono-atomic it changes the partial pressure of water vapor ensuring the cookies (or whatever) stay dry (desiccates bacteria too). The best answer would be to get it from the horses-mouth. The packaging will have either a web address or customer care-line number, consumer services department or something. Google the company to find their contact us details and send them an email. When I worked in industry we often received these sort of odd-ball inquires and we answered them the best we could. It was viewed as an important part of PR. So I can guarantee you, that you will get a reply.--Aspro (talk) 21:10, 4 May 2016 (UTC)

Note that the hissing sound during opening doesn't necessarily mean it was stored under reduced pressure intentionally. Either it might just have happened to be in a slightly different air pressure environment when it was sealed than when it was opened, or the act of opening the package may itself increase the volume, and thus decrease the pressure, as pulling the cork out of a wine bottle does. StuRat (talk) 14:58, 5 May 2016 (UTC)

The hissing also seems to be evidence the container was well sealed, and presumably helps reinforce the customer's trust in the hygiene of the product. This is also OR, but I note StuRat's idea above, though reasonable, suggests we should see an outflow of air frequently from products packed at sea level (especially since so much comes by ship). Yet I've never seen an outflow of air, because everyone associates it with botulism beans and such. In good, out bad, and that seems reflected in the marketplace. Wnt (talk) 21:10, 5 May 2016 (UTC)

It's rather shameful that nobody mentioned the vacuum packing article before now, which says potato chips may be packed in nitrogen. Wnt (talk) 10:25, 8 May 2016 (UTC)

Somme river flooding

Hello,

How often and how severely does the Somme river in France flood? Where can I find data on this? — Preceding unsigned comment added by 140.233.173.140 (talk) 20:46, 4 May 2016 (UTC)

Our article Somme (river) has statistics for the past few decades, and the French article fr:Somme (fleuve) has more data. From the latter: « Les crues, quant à elles, sont rarement importantes, sauf en cas de saturation de la nappe phréatique, comme ce fut le cas en avril 2001. » - approximately translated "Floods, on the other hand, are rarely significant, except when saturation of the water table occurs, as was the case in April 2001". Tevildo (talk) 23:18, 4 May 2016 (UTC)

So, for example, around how often do significant floods occur? (significant as in may have caused significant damage to a medieval town) I'm a bit confused by the data. — Preceding unsigned comment added by 140.233.173.140 (talk) 01:02, 5 May 2016 (UTC)

This has a timeline (page 6) and this discusses things to some extent. I googled inondation somme Thincat (talk) 08:28, 5 May 2016 (UTC)

May 5

Extinction vs. evolution of defense mechanisms

Why is that some groups of animals manage to evolve defensive mechanisms against predators and other threats, while other animals (sometimes from the same taxonomic rank) do not evolve anything and become extinct? Is it about population size and slow rate of predation? Thanks. 93.174.25.12 (talk) 14:24, 5 May 2016 (UTC)

It's virtually impossible to say with certainty exactly why similar scenarios can turn out differently in evolutionary history. Lots and lots of factors come into play, and we are not really able to do controlled experiments for these scenarios. But yes, you basically have the right idea. I'll say a little more about the factors and give you some refs that will help you think about this issue: Selective pressure e.g. through predation comes in various strengths. Too low and it won't have much effect, too high and the species is wiped out right away. Allee effects can come into play for very small populations, and in that scenario, random chance can play a big role too. Alternative stable states discusses a little bit about how random fluctuation can lead to different outcomes in ecological models. Apparent competition provides another way of looking at this. If a predator P preys on species A and B, then the dynamics of A and B are actually similar to when A and B compete for a single resource R, because of the predator's prey switching. This gets in to top-down vs. bottom-up control of ecosystems, by species at different places in the food web, see here [11] for a brief description of those effects and here [12] for a scholarly review article. Finally, note that in the case where one predator P eats one species A almost exclusively, they will have strong pressure to not eat all of A, because if they did, P could go extinct too. So that's a very broad overview of the forces that influence whether species persist in a sort of Red Queen race or whether one or more go extinct. If you have further questions or would like more specific references let me know and I'm happy to provide more info. SemanticMantis (talk) 14:43, 5 May 2016 (UTC)

(ec) Note that extinction isn't just caused by predation, there's also a loss of habitat, food supply, climate change, disease, etc. One way in which predators can wipe out a species is if an invasive species is introduced which is far more capable than the prey, not giving the prey the time they would need to make massive adaptations. Species limited to islands with no natural predators are particularly vulnerable, like the dodo. On the other hand, if a predator in the same environment slowly evolves more capability to hunt the prey, the prey can evolve an ability to survive that predator at about the same rate. StuRat (talk) 14:45, 5 May 2016 (UTC)

Yes, the dodo, and also the Moa. Akld guy (talk) 04:59, 6 May 2016 (UTC)

Evolution is the summation of random mutations that enables a life form to compete. If they find that their Ecological niche is suddenly changing due to say climates changes or/and other predators or animals that are better at competing for the limited food supply moving in, then they may not be able to evolve quickly enough to adapt. This goes for other things as well. Take Microsoft. In the early years it was a predator. Now it a grown to be a slow moving giant dinosaur, leaving other more adaptive critters to nip at it ankles take away the food it needs, because they have better evolved and can do so more quickly.--Aspro (talk) 14:56, 5 May 2016 (UTC)

• Relevent here is Survivorship bias. Much of people's misunderstanding about evolution comes with the notion that, while mutations are random and capricious and arbitrary, only mutations which have "survived" are evident long enough to leave a significant record, so we have the mistaken sense that evolution has a purpose or a goal or makes living things "better". --Jayron32 16:10, 5 May 2016 (UTC)

I am actually suspicious that a species can go extinct through lack of predation. The dodo is a classic example, though some now say it has been misrepresented. If members of a species do not periodically make a run for their lives, will they continue to be able to run? Etc. Of course, the dodo never actually became too weak to move ... it just reached a point where it couldn't handle a sudden change for the worse. A species facing many predators is already at worse, and can't be so greatly surprised. I even wonder if a prey species tends to evolve a top speed that just barely ensures the predators will keep getting fed with its weaker members, though that would be in a sense a pretty remarkable extreme of altruism, already a controversial concept. But I have not really seen anything about this. Wnt (talk) 21:02, 5 May 2016 (UTC)

Hey @Wnt: do you mean you suspect lack of predation can cause extinction? Resource competition models show how species can go extinct with no predation. All you need is an uptake rate that's faster than the supply rate. Tilman's R*_rule_(ecology) is relevant here, see also [13] [14] [15]. But there's no predator even in the picture there. To get at the notion of lack or too little predation, you'd want to have a fairly stable system with say one predator, two consumers, and one resource, then show that removing the predator can cause one of the consumers to go extinct. In concept this could be investigated with microcosms, but I don't know as much about that. For the theory, check out my colleagues Chesson and Kuang (2008) [16] or maybe some of their other work [17]. I don't know if they have this specific scenario covered, but I suspect they do. Ecological modeling his hard, evolutionary modeling is hard, food web modeling is hard, and very few people have been bold/crazy enough to try to understand all three interacting. There are some simulation models out there that get pretty complicated, but depending on your epistemic stance, those don't really tell us anything about the real world. Then again, depending on your epistemic stance, no model no tells us anything about the real world ;) SemanticMantis (talk) 21:58, 5 May 2016 (UTC)

@SemanticMantis: Great answer - it is indeed hard. Even reality seems like a bad model, to be honest. For example, in the case of the Lake Guri howler monkeys, the long-term effect of losing a predator in the abstract is overwhelmed by the effect of huge extremes in population that occur immediately. It's like you have to ask what would happen if overgrazing yields a new equilibrium over many years that is not different from the old equilibrium, then would the predator's absence also cause specific changes in the former prey? It's not even really a coherent question, I guess. At least, I'm not sure how to frame it properly. Wnt (talk) 22:45, 5 May 2016 (UTC)

@Wnt: I wonder if you're getting at the distinction of neutrally stable cycles vs. stable limit cycles. For example in the classic Lotka-Volterra predator prey model, there is nothing to stabilize a preferred amplitude, and both species can come arbitrarily close to zero. This is very different from some other systems/ models, but if you look at the famous Hudson Bay data for lynx and hare pelts [18](I can't find our copy of this graph), you can see there's no clear lower limit to the fluctuations. It is hard to properly phrase the questions and comments, but if you want to continue the discussion, feel free to drop by my talk page. SemanticMantis (talk) 14:01, 6 May 2016 (UTC)

Percent deviation from additivity

What is the quantitative expression associated to the verbal phrase +/_x % deviation (expansion or contraction) from the addivity of volumes in water ethanol or water salt/sugar solutions?--85.121.32.1 (talk) 15:47, 5 May 2016 (UTC)

Could it be a fraction whose numerator include the difference between the volume of the mixture V and the volumes of the two components V1 and V2 and the denominator equals the sum V1+V2:

$\%\Delta V_{r}={\frac {V-(V_{1}+V_{2})}{V_{1}+V_{2}}}100$?--85.121.32.1 (talk) 15:52, 5 May 2016 (UTC)

or $\%\Delta V_{r}={\frac {V-(V_{1}+V_{2})}{V}}100$?

Which one of these two variants of this fraction which can be called relative volume difference are more appropiate?--85.121.32.1 (talk) 15:15, 6 May 2016 (UTC)

Is this question too complicated or intimidating for someone from here to attack it? (just a thought)--85.121.32.1 (talk) 15:32, 6 May 2016 (UTC)

I think it's a mainly a language problem. If you post the complete sentence as originally written, it'll be easier for us to work out the meaning. If the original sentence isn't in English, we'll probably also be able to provide a good translation. Tevildo (talk) 20:42, 6 May 2016 (UTC)

Doing some digging, I believe the problem sentence is in Apparent molar property#Alcohol, and I must admit that I don't understand it either. The sentence is:

“ The nonideality of the solution is reflected by a slight decrease (roughly 2.2%, 1.0326 rather than 1.055 L/kg) in the volume of the combined system upon mixing. ”

My question (which I think mirrors that of the OP) is (a) 2.2% of what?, and (b) where does the 1.055 L/kg come from? 1.0326 L/kg is the specific volume of a 20% w/w mixture of ethanol and water. Tevildo (talk) 07:43, 7 May 2016 (UTC)

Medical Satire

Thinking of putting this suggestion up to Wikipedia:WikiProject Requested articles but would like your comments first, as the editors here seem to have both feet on the ground.

Something, I have had simmering on my back burner for years, is that Wikipedia doesn't have an article on Medical Satire yet. There is a lot of it about – one could even say that it is a chronic pandemic. It is my (personal) belief, that it has a slow incubation period, starting in the early twenty’s (at the same time when protection of one's parental antibodies wains) with signs an symptoms only becoming manifest in the mid-thirties. Until such time, that medical science can come up with a effective treatment for this malady, is there any Quacks Doctors/nurses/radiographers/hospital porters/morticians/ etc., that can help me to put such an article together?--Aspro (talk) 17:13, 5 May 2016 (UTC)

You're talking about this [19] sort of thing, right? Here's [20] [21] some refs to get you started, lots of refs therein too. I would not have guessed the genre could trace its roots back to the 17th century! SemanticMantis (talk) 18:31, 5 May 2016 (UTC)

I don't think Wikipedia needs an article about every combination of literary form and subject matter. Is there something about satire of medicine that makes it more than the sum of its parts? -- BenRG (talk) 19:15, 5 May 2016 (UTC)

Well, we already have Political satire and Religious satire (despite "multiple issues"), also Comedy of manners. Alansplodge (talk) 17:51, 6 May 2016 (UTC)

Well, those articles sort of illustrate what I'm afraid the medical satire article would be: some boilerplate text along the lines of "satire of X has existed for as long as X; it is a way of avoiding cultural taboos surrounding the direct criticism of X; it can provide valuable insight into the popular perception of X at different points in history", etc., followed by the intersection of "list of works about X" and "list of satirical works". To be fair, there might be value in a separate list of historically important satire about medicine. -- BenRG (talk) 21:23, 7 May 2016 (UTC)

Tiltwinged and thrust vectoring airliners

Thrust vectoring says it's not currently used on commercial aircraft. In practice, what are chances of a commercial airliner with a sort of tiltwings that tilt to a desired angle and thrust vectoring engines for better control of the angle of attack? Costs aside, my understanding is that it would reduce (or eliminate) the possibility of stalling, diving, flat spins and other undesirable aerodynamic effects, so that even in case of pilot error (like Pulkovo Aviation Enterprise Flight 612) the proper airflow could be restored. Brandmeister^talk 20:38, 5 May 2016 (UTC)

If such things as tiltwings, tiltrotors, variable-sweep wings, variable-incidence wings and thrust vectoring were considered cost efficient, we would already have operational commercial aircraft with one or more of these features. Since we don't, I have to assume that the cost (in regard to money, weight and added complexity) of adding such features outweighs the benefits of them. WegianWarrior (talk) 21:04, 5 May 2016 (UTC)

I know nothing about this, but I had an impression the Bell Boeing V-22 Osprey was not a particularly safe aircraft. Does the benefit of having all those fancy features available for emergencies really outweigh the odds that something going wrong with them will cause an emergency in the first place? Wnt (talk) 22:33, 5 May 2016 (UTC)

A predecessor of the proposed Boeing 2707 supersonic transport was planned to have had "swing wings" (variable geometry), but they made the aircraft too heavy and the final design had a delta wing rather like Concorde. Alansplodge (talk) 22:44, 5 May 2016 (UTC)

The Concorde did have a movable nose cone, which allowed them to switch from a position with better visibility to one with better aerodynamics. However, the Concorde, despite being used for decades, didn't really prove to be commercially viable in the long term (only 14 were ever put into service). StuRat (talk) 15:00, 6 May 2016 (UTC)

All of the concerns listed are minuscule in commercial aviation. Stalling, uncontrolled diving and spins (of any type) are virtually unheard of. Notable cases such as the Airbus out of Brazil would likely still have a stall/spin because it was commanded. I'd be more keen on ideas like supercruise that allow fuel efficient supersonic transport. Also, efficient high-altitude jet design would be a higher priority, imo. --DHeyward (talk) 09:04, 6 May 2016 (UTC)

Agreed. While all of those high-tech additional moving parts might help a fighter plane during a dogfight, just flying more conservatively is enough to make them unnecessary for commercial aircraft. StuRat (talk) 15:00, 6 May 2016 (UTC)

According to Accidents and incidents involving the V-22 Osprey; "The V-22 Osprey had 7 hull-loss accidents with a total of 36 fatalities. During testing from 1991 to 2000 there were four crashes resulting in 30 fatalities. Since becoming operational in 2007, the V-22 has had three crashes resulting in six fatalities including one combat-zone crash, and several minor incidents." Alansplodge (talk) 17:43, 6 May 2016 (UTC)

Infact all modern commercial airliners have Thrust reversal-"Thrust vectoring" as brake. Beyond that vectoring and Variable-sweep wing make no sense for big planes and with very few, very expensive exeptions, like the Rockwell B-1 Lancer and Tupolev Tu-160, there are no Variable-sweep wings on huge planes because they "only" give you more speed for a very high price and additional risks. Just imagine you would have to make shure a Airbus A380 with defective variable-sweep wing, fixed in its deltawing travel settings, would need to be able to land on an already "almost to short for this giant plane" airstrip. --Kharon (talk) 01:17, 8 May 2016 (UTC)

Could we be in a black hole right now?

Could we (Earth and visible universe) be inside a black hole right now and since the beginning of times? --Llaanngg (talk) 22:35, 5 May 2016 (UTC)

See Black-hole_cosmology. Some people find this idea convincing, others don't. I'm not even sure if it's a falsifiable claim or not. SemanticMantis (talk) 22:46, 5 May 2016 (UTC)

This exact same question was asked just last month. Vespine (talk) 23:08, 5 May 2016 (UTC)

And yet, nobody had linked our most relevant article in that thread. I skipped that round because I don't know much about this topic. But this time I looked around a bit because I felt the last round was unsatisfactory, though there is what looks to be expert commentary from Ben there. Anyway, sometimes it's ok to ask the same question again- sometimes you get different and possibly better references. SemanticMantis (talk) 13:54, 6 May 2016 (UTC)

An antidepressant

I just found out by accident that citalopram, a rather popular antidepressant, is a salt of Hydrobromic Acid. Good Lord, it is a very strong mineral acid. To have it in the GI tract on a daily basis... Isn't it dangerous? --AboutFace 22 (talk) 22:42, 5 May 2016 (UTC)

Salt (i.e. table salt) is a salt (chemistry) of hydrochloric acid. The neutralization of an acid into something more neutral is what makes a salt a salt. Wnt (talk) 22:47, 5 May 2016 (UTC)

There a comprehensive list of adverse effects here. There are not any GI track specific effects though, only related to SSRI discontinuation syndrome. --Llaanngg (talk) 23:23, 5 May 2016 (UTC)

You know your stomach is filled with acid, right? An enormous number of drugs are administered as salts, often hydrochloride salts. --71.110.8.102 (talk) —Preceding undated comment added 05:50, 6 May 2016 (UTC)

As above. Your stomach is already at pH 1.5-3.5 (gastric acid, a few mgs more acid isn't going to do much. 213.105.166.119 (talk) 06:46, 6 May 2016 (UTC)

May 6

What happens if long enough rope is on earth?

49.135.2.215 (talk) 01:26, 6 May 2016 (UTC)Like sushi

What? Evan ^{(talk|contribs)} 01:27, 6 May 2016 (UTC)

Earth destroyed by black hole. Sagittarian Milky Way (talk) 02:06, 6 May 2016 (UTC)

Didn't somebody ask this like a week ago? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:08, 6 May 2016 (UTC)

You can use it for a space elevator. It had better be a really strong rope though. --71.110.8.102 (talk) 06:15, 6 May 2016 (UTC)

I imagine it will be like the infamous "piece of string" - always just slightly too short for whatever it is needed for. 81.132.106.10 (talk) 09:03, 6 May 2016 (UTC)

If a long rope is on Earth, well, a long rope is on Earth. ThePlatypusofDoom (Talk) 12:29, 7 May 2016 (UTC)

The Earth will hang itself.--Heron (talk) 07:36, 8 May 2016 (UTC)

pressure enough to make "carbon string"?

(I can not be watching)

49.135.2.215 (talk) 01:28, 6 May 2016 (UTC)Like sushi

Read Carbon fibers, Carbon nanotube and Linear acetylenic carbon. High pressure may not be required. Graeme Bartlett (talk) 11:18, 6 May 2016 (UTC)

Edible-nest swiftlet

Our article on the subject is quite poor. I was wondering if anyone knows the average weight of each nest?Lihaas (talk) 10:17, 6 May 2016 (UTC)

The German article (de:Weißnestsalangane) says: "Der Durchmesser beträgt ungefähr 6, die Höhe 1,5 Zentimeter, das Gewicht liegt bei ungefähr 14 Gramm." (diameter 6cm, height 1.5 cm, weight around 14 grams). --Wrongfilter (talk) 10:31, 6 May 2016 (UTC)

Thanks

Man, it takes a heck of a lot to make 1 kg...which sells for some $2000.Lihaas (talk) 13:41, 6 May 2016 (UTC)

So about 28 cents apiece: have a look at what they have to do to collect them. Alansplodge (talk) 17:38, 6 May 2016 (UTC)

Isn't that 28 dollars apiece ? StuRat (talk) 03:55, 7 May 2016 (UTC)

D'oh! Quite right StuRat, $28 each. Still, I suspect that's the wholesale price rather than what the chap at the top of a precarious ladder gets. Alansplodge (talk) 13:35, 8 May 2016 (UTC)

I like how the video clearly states that the nest has no nutritional value and adds no flavor. I bet it's a heck of an interesting texture though :) SemanticMantis (talk) 17:49, 6 May 2016 (UTC)

I dunno about the youtube video but it makes sense at about 30 or so dollars...and its apparently rich in protein but an acquired taste.Lihaas (talk) 12:42, 7 May 2016 (UTC)

@Alansplodge: Theyre farmed too. (hence easier)Lihaas (talk) 13:06, 8 May 2016 (UTC)

Thanks Lihaas. Gosh, I don't know how I missed swiftletfarming.blogspot. Alansplodge (talk) 13:35, 8 May 2016 (UTC)

Extracellular sodium channel blockers vs. intracellular sodium channel blockers

Sodium channel blocker lists both extracellular and intracellular classes of these substances. I noticed that the intracellular forms include several crucial drugs, including a number of WHO-EM drugs (lidocaine, bupivacaine, procainamide, quinidine, phenytoin, carbamazepine), whereas the extracellular forms are some of the most lethal neurotoxins known (saxitoxins, neosaxitoxins, and tetrodotoxins). It would seem that blocking one side of the sodium channel versus the other makes a significant difference, but what exactly is that difference? —/Mendaliv/^2¢/_Δ's/ 20:39, 6 May 2016 (UTC)

Excellent question! Two thoughts. First, the sodium channel that both TTX and lidocaine act upon is a voltage-gated sodium channel. This means that, unlike the ligand-gated nicotinic sodium / potassium channel, the voltage gated sodium channel is not meant (evolved) to be activated / deactivated / inactivated / deinactivated by a neurotransmitter (ligand) molecule binding to it from the outside. So, whatever molecule binds to it from the outside and blocks it, is either a toxin or a drug, and not a part of a natural physiological processes taking place in the organism. Second, there is no strict way to distinguish between a "poison" and a "drug" - it is purely a question of dosage and intended (or unintended) effect. Toxins are poisons produced by living organisms. It so happens that TTX is used by some fish and amphibian species to protect themselves; so it is ingested by the predator and acts on the predator's neurons from the outside instead of being transported into the neurons first. There are toxins that are transported into the cell, too: for example colchicine or taxanes that interfere with cell division, or Tetanus toxin that blocks neurotransmitter release into the synaptic cleft. But for a fast-acting toxin your best bet is to block the action potential generation and propagation or synaptic transmission from the outside of the neurons, which is what most fast-acting toxins do. --Dr Dima (talk) 22:13, 6 May 2016 (UTC) Continued: as to why the voltage-gated sodium channel "blockers" (actually, mostly modulators) found in medical use bind to the intra-cellular sites of the sodium channel - it may be by chance (novocain was discovered in 1905, long before the sodium channel itself was discovered). Or it may be because binding to the intra-cellular sites allows to modulate, rather than physically block, the channel, which may be advantageous in medical applications. --Dr Dima (talk) 22:50, 6 May 2016 (UTC)

What I can say for sure so far is that an answer for this one won't be easy. There seem to be some different effects of the two types of drugs, [22] and allegedly (I don't know if this is reproducible) the extracellular toxins also do something to calcium channels ... something subtle. [23] The local anaesthetics affect TTX-resistant channels. [24] There are literally hundreds of papers in PubMed that discuss tetrodotoxin and lidocaine somehow or other, and they're not the easiest papers to read... (Here's another one that might be informative, modeling extracellular access of drugs, but it is not finger food) One trivial thing is TTX is simply longer-acting, [25] but that doesn't really explain it when a drug is taken with the intent of long-term inhibition. Hmmm, hit #249 is a goodun: [26] says "The contrasting patterns of effects between TTX and local anaesthetics suggest that blockade of TTX-sensitive sodium channels alone may not be responsible for the effects of cocaine, lignocaine and benzocaine." That's kind of ancient, but there is TTX-R stuff about lidocaine coming out to the current day: [27] Wnt (talk) 00:18, 7 May 2016 (UTC)

Magnetic quantum number

I recently did some major rewriting at magnetic quantum number, and have a leftover sentence about Larmor precession. The problem is, I have no idea how to relate it to the article. As best as I could figure out looking at a few web sources, the Larmor frequency is a function of the atom, not the m of a particular electron therein, and so electrons with any given m all precess at the same frequency?

Bonus question: I was kind of wondering where the angular momentum goes if multiple photons hit an atom. For example, you have a hydrogen atom with bright multiple frequencies of light shining on it. The first photon carries sqrt(2) reduced Planck units of angular momentum and knocks the atom from its base state (0) to the first level (sqrt(1*2)); all the angular momentum is conserved. But any photons after that knock it up by a smaller amount, not much more than 1, because sqrt(l(l+1)) approximates to l+0.5. Now I suppose this is reversible - it could emit back out photons with the same total angular momentum - and so in a sense the momentum is conserved. But the vector isn't! Or am I missing something... (I'm thinking this is something about how random angular momentum adds up ... but in which direction(s)?)

Anyway, I'd much welcome some eyes at magnetic quantum number to see if I screwed it up badly. Wnt (talk) 21:29, 6 May 2016 (UTC)

Also, I think there is no way to tell by looking at the shape of the orbital whether it has a +m or -m (but you can tell the absolute value of m). This would be the equivalent of seeing a map of a planet's orbit and not knowing from that alone which way the planet is headed. But can someone confirm with a source?

Hydrogen 6h orbital, with m=-5. The electron wave cycles through its complex phase five times going around a large circle. With m=5, it cycles in the opposite direction... as if moving through these phases from one lobe to the next.

More generally, it would be nice to get a more intuitive feeling here. If you look at a hydrogen and you see it has a p_x electron, that electron has an angular momentum around the z axis. Does this truly mean that the electron is orbiting in some sense, i.e. that over time it is moving either clockwise or counterclockwise about the z axis? Now there are some real howlers about the meaning of the + and - lobes of orbitals online, but my understanding is that they represent the phases of a wave, and that in intuitive terms this means - correct me if I'm wrong, and this sounds wrong! - that if we somehow could know where the electron really was in the orbital without disturbing its momentum, then in some short time (how short?) it would fall through the nodal plane and turn p in the other sign of lobe in something like half the Bohr orbital period (half of 150 as, according to page 9, but does this get larger with principal quantum number? I'd guess so, and that the extra time corresponds to the extra little lobes near the nucleus in 3p orbitals and up, which it has to pass through?) And so I take the angular momentum to possibly indicate that the electron in a p orbital jumps from lobe to lobe via a course that goes a particular direction around the nucleus? But at some point the analogy seems to break down since the electron jumps over a nodal plane, something with no apparent particle-mechanics analogy. Wnt (talk) 14:29, 7 May 2016 (UTC)

It "jumps over a nodal plane, something with no apparent particle-mechanics analogy"? Exactly! Because it's a wave-like/particle-like entity, not quite either one. Even on a plucked guitar-string, one can easily see stationary points. If one is very careful (and my quantum-mechanics prof was awesome at this!) one can lightly place a finger at half the guitar's length, pluck the string, and then remove finger...both halves of the string vibrate, and the guitar is stably emitting an octave higher than normal. The hand-wave(ha!)-ing explanation is that the electron (if you are still thinking it's a particle that has discrete positions at specific times) can tunnel across the node. The wave explanation is that there is just a node on the single wavefunction, so "the wave" is on both sides simultaneously, or the string need not "move" the middle in order to be moving on both sides. wikiquote:Quantum mechanics has some good comments from experts about how often QM does not make self-consistent macroscopic/real-world sense. DMacks (talk) 21:03, 7 May 2016 (UTC)

@DMacks: I recognize that many sources say QM is hard to understand. But I remain unsure when and how much those limits can be pushed. What emboldens me most is that alternating current can be written in similar crazy notation, with phase angles and complex numbers. Yet it has an intuitively comprehensible basis. So I feel like I shouldn't give up trying to find one here. I am thinking (not sure) that if you look at the f orbital diagram I added to the article, that you can sort of see how an f orbital with m=0 is vibrating up and down between lobes in the z-axis, and one with m=1 is orbiting in something like an x-z plane from lobe to lobe, with only a slight motion around the z axis, whereas the m=3 case is more or less the same orbit, but now totally in the xy plane so that all the angular momentum is around the z axis. The motion from lobe to lobe (or node to node) would seem to mark some kind of path...

Which gets me to another question, I suppose. If you "lightly measure" a population of electrons to be within one particular lobe of an f orbital, say, can you measure them within attoseconds later and see that they may move to the adjacent lobes, but not all the way to the lobe on the far side of the atom? Wnt (talk) 01:02, 8 May 2016 (UTC)

For an analogy of the "is the electron moving or not" question, consider a flashlight/laser beam shining continuously on an absorbent (dark) surface. The light has momentum (pointing along the direction of the beam, toward its destination). But the situation is also time-independent. Is the light moving? In some sense yes, in some sense no. It's the same question for the electron orbits. That it's a quantum wave function, and the motion is circular instead of linear, doesn't matter as far as this question goes. The electron orbits in the same sense that the light moves.

For a classical analogy of "jumping through nodes" consider a standing wave. You can think of a standing wave in one dimension as a superposition of left-moving and right-moving waves. Is the light (or whatever) moving left and right through the nodes? I don't know, but whatever your answer is in the classical case, that's the answer in the quantum case too. -- BenRG (talk) 17:46, 8 May 2016 (UTC)

Maybe I'm being simple-minded here, but I feel like if an electron has energy and angular momentum it has to be moving. Still, the whole question may be complicated. It seems like one guy at the center of what has been published lately on attosecond transient absorption spectroscopy, who was looking at things like the transition of an electron from 4d orbitals to Rydberg atoms, says "Such a noble-gas ion which inherits a hole in the valence p_z orbital is not anymore in an eigenstate but rather in a superposition of different quantum states." And what he can do seems a lot blunter than what I wanted, looking at where an electron is in an orbital and then looking a few attoseconds later, which for now still seems like nothing but a thought experiment AFAICT. This is all far beyond my understanding. Honestly, I'm still not really understanding what that ring diagram I added above really means - the complex phases are normally shown as spaces between orbital lobes, but in this series of images, even for p orbitals (except along the z axis! due to multiple possible orientations superimposed?), they are shown as linkages, probably the very "orbits" I was looking to see. But dang it, if only I got what the e^itheta in these solutions "really means", and comprehended how these segments are bricked together to build up orbitals, I feel like a lot of quantum mechanics would be very intuitive. Wnt (talk) 20:16, 8 May 2016 (UTC)

Does petting an human release endorphins?

In the past I've heard explanation why people are relaxed while getting petting, but I forgot the explanation. Is it because that the body release endorphins? (I know for sure that it releases the hormone oxytocin but I'm not sure about the endorphins) 93.126.95.68 (talk) 23:28, 6 May 2016 (UTC)

Probably more so than with your average dog or cat. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:38, 6 May 2016 (UTC)

Apparently so. Complementary Psychosocial Interventions in Child and Adolescent Psychiatry: Pet Assisted Therapy--Aspro (talk) 23:45, 6 May 2016 (UTC)

If I'm nor mistaken, this article deals with petting pets rather than petting human. Am I right? 93.126.95.68 (talk) 23:54, 6 May 2016 (UTC)

Am I right or mistaken that humans are animals also!--Aspro (talk) 00:32, 7 May 2016 (UTC)

"petting" is a fairly antiquated term for physical affection...like "heavy petting" instead of "making out"...the OP is using the term in this manner...68.48.241.158 (talk) 01:51, 7 May 2016 (UTC)

I doubt it releases Oxycontin. You were probably thinking of oxytocin. --71.110.8.102 (talk) 04:46, 7 May 2016 (UTC)

Thank you, I corrected it. 93.126.95.68 (talk) 12:20, 7 May 2016 (UTC)

According to Dr Nor Ashikin Mokhtar, there are many hormones and neurotransmitters released during foreplay but oxytocin and endorphins only seem to be released during an orgasm. Richerman (talk) 08:00, 7 May 2016 (UTC)

According to the article oxytocin "In a 2003 study, both humans and dog oxytocin levels in the blood rose after five to 24 minutes of a petting session."93.126.95.68 (talk) 12:22, 7 May 2016 (UTC)

May 7

Mechanisms and or Functionalities sought

Apparently this exists in the game. If so,

1. What's the mechanism(s)/functionality(s)
2. How it does what it is suppose to do?

Apostle (talk) 09:45, 7 May 2016 (UTC)

When I googled world of warplanes ufo mechanism, I came to this site. Take note of the date (April 1) and the comment "Thanks for laughing along with us on April 1st!" under the picture and see if you can come to any conclusions on your own. In the future, questions about games should probably go in the Entertainment desk. Matt Deres (talk) 12:16, 7 May 2016 (UTC)

For proposed actual use of flying saucers in the military, see Avrocar. StuRat (talk) 15:09, 7 May 2016 (UTC)

Unsatisfying. Thank you (both) anyway -- Apostle (talk) 18:40, 7 May 2016 (UTC)

Place with the largest observable part of the other celestial hemisphere

In what place on Earth the largest part of the other celestial hemisphere could be observed at night (such as in northern celestial hemisphere with the largest number of southern hemisphere objects or vice versa)? Thanks.--93.174.25.12 (talk) 13:47, 7 May 2016 (UTC)

The closer you get to the equator, the more of the "other" celestial hemisphere you should be able to see. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:55, 7 May 2016 (UTC)

A tall vantage point should help as well. Combining the two, Chimborazo should be a good choice. Kilimanjaro wouldn't be a bad choice either. --82.164.37.199 (talk) 14:34, 7 May 2016 (UTC)

preheating oven pointless?

I notice that to put food in I have to basically open the door all the way and for at least 2 or 3 seconds...all the hot air is let out..if google "preheating oven pointless" a lot comes up to suggest it's true....true??68.48.241.158 (talk) 16:36, 7 May 2016 (UTC)

No, definitely not pointless because the thermal capacity of the heating elements and the metal structure of the oven far exceeds the thermal capacity of the air released on opening. The cooler air that flows in is quickly heated to the temperature of the metal that surrounds it. Dbfirs 16:40, 7 May 2016 (UTC)

what you say is scientifically true, of course...I wonder about the practical difference...is there that much of a significant practical difference considering how quickly modern ovens heat up...??68.48.241.158 (talk) 16:51, 7 May 2016 (UTC)

Yes, I was thinking of older ovens with a high thermal capacity. If the oven heats up to the required temperature in a few seconds, then pre-heating is indeed almost pointless, but only my small halogen oven does this. Dbfirs 16:58, 7 May 2016 (UTC)

well, seems like it get to 400F in 6 or 7 minutes...to 300F in 4 or 5 minutes...68.48.241.158 (talk) 17:05, 7 May 2016 (UTC)

It also depends on what you are using your oven for. Baking often needs a constant even temperature for a relatively short time, so pre-heating is important. If you are roasting a joint then you can just add five minutes to your cooking time instead of pre-heating. Dbfirs 17:09, 7 May 2016 (UTC)

Preheating where needed is probably not mostly about times or temperatures. These are factors, but the biggest one is probably that during heating the elements or burners give of a lot of infrared which may not be want you want. BTW, this was discussed before on the RD, see Wikipedia:Reference desk/Archives/Science/2009 October 9#Why preheat the oven?

You gave figures for how long it takes to reach the desired temperature from cold, but not how long it takes to return to the temperature after opening (if the elements even come on again). If it's 1 minutes vs 4 minutes this is still a very big difference if the total time is short. Note that if you've been using an oven enough with a variety of different things, it's not that hard to see how big a difference having the elements on as well as not preheating can make.

Also if you read some of the results from your search, you'll likely find people with similar comments e.g. [28] [29] [30]. There are a few who appear to be speaking from actual experience (rather than simply theoretical which to be frank is likely too spherical cow to be useful) e.g. [31] (and some of the comments in the discussions) but it's not always clear what the specific experience involves.

I'm sure people preheat in a lot of cases where it's not really particularly useful. And I'm sure preheating with modern ovens and smaller ones is often less important than with older ones and larger ones. But this is different from saying preheating is always useless (other than for time saving if you remember to preheat during prep) with most resonable size home ovens.

Nil Einne (talk) 20:39, 7 May 2016 (UTC)

I imagine for things like roast potatoes that bringing them slowly up to temperature in a bath of cold duck fat would result in a quite different outcome to dropping them into hot fat. Similarly with roast chicken, the skin would dry rather than crisp. For stews and the like I doubt it makes much odds. Greglocock (talk) 00:01, 8 May 2016 (UTC)

Its simply a timing issue, because recipies need to set a reliable time frame to cook or roast something properly. For one oven may need 15 minutes and another only 5 minutes to heat up, you can not include that. With some cooking experience you can estimate and include the preheating phase with your oven and very likely save some time. --Kharon (talk) 00:53, 8 May 2016 (UTC)

May 8

Paint color matching.

When I take a chip of paint to a DIY store and have them make a matching paint - what kind of sensor do they use? Seems like a regular RGB camera wouldn't cut it...do they switch light sources? How does it actually work?

SteveBaker (talk) 02:21, 8 May 2016 (UTC)

Colorimeter?--178.107.62.251 (talk) 03:34, 8 May 2016 (UTC)

One actually can use a regular camera, for example, Sherwin-Williams has an app.[32] DMacks (talk) 04:13, 8 May 2016 (UTC)

Not sure how good it is, but [33] has some technical discussion. That and other sources like [34] [35] (second one is about car paint colour matching) says a spectrophotometer. One source I came across called it a Spectroradiometry, but I think photometer is more accurate for the type of machine normally used. Admitedly I wonder if spectrocolorimeter may be even more accurate for what being done, but I didn't read enough to know for sure.

Anyway I found this PR about one machine used [36] which may help find out PR about this specific machine [37], if you cut through the PR I would guess you could get some info on what's actually involved. Colour Match Navi CT-X is evidentally one device used for cars although I could find very little about it. The device mentioned in the Gizmodo link is more productive [38]. I also noticed a lot of AliBaba results e.g. [39], I would guess some stores are using products sold there.

I would also assume/hope, there must be some published science about these commercial computerised paint colour matching machines, I didn't notice any but a targeted search may work better.

Nil Einne (talk) 14:23, 8 May 2016 (UTC)

Mobile phones in walkie-talkie mode - range?

I understand that a mobile phone connecting directly to another mobile phone instead of via a cell tower would have greatly diminished range because the cell tower provides the power so that the phone doesn't have to but what would that range be? Using the hardware usually used to connect to the nearest cell tower, how far could phones talk to each other in a such a walkie-talkie mode? — Preceding unsigned comment added by 78.148.108.58 (talk) 19:52, 8 May 2016 (UTC)

This question really devolves pretty quickly when you start getting into technical details. Cellular networks are specifically designed to be asymmetric, not peer-to-peer; and this design is embodied in every detail of the hardware, from the amplifier design to the antenna design to the frequency choice to the digital and software protocols that are used. A significant limiting factor - perhaps the most significant limiting factor - is the nature of the shared channel, and if we re-architected a mobile phone for direct peer-to-peer operation, this changes everything about the communication signal quality. Every single detail of your mobile telephone's radio is defined by its mechanism for cooperatively sharing that channel with a tower and with other users. So, we simply can't answer the original question as posed - not accurately - because cellular telephone electronics don't work in this mode. If we start changing details or making approximations, we haven't got a cellular telephone anymore.

How familiar are you with radio technology? Before we start lobbing specifications at you, it might be good for you to review some basic terminology for telecommunications engineering and radio-frequency engineering.

At best, we could show you some specifications for other types of radios whose size and shape are "similar" to mobile cellular telephones. For example, a handheld VHF radiotelephone for use at aviation radio frequencies will reach one or two miles (if you're on the ground); and you might manage to reach as far as ten or twenty miles if you're at altitude - say, two miles above the ground, with a clear line of sight to your remote station. Aviation VHF is quite a bit lower frequency than the bands used by a modern mobile cellular telephone. To first-order approximation, that means that your cellular telephone will have a shorter range and will be much more limited by any obstacles (like walls, buildings, and terrain, and even humidity in the atmosphere) that block your line-of-sight.

I happened to be reading this article - on natural antennas - earlier this weekend. It's fascinating to see some cold, hard numbers - a 15 watt HF radio (which is much lower frequency and much much much much greater power than your mobile telephone) will work over a few miles through dense forest; but if you use a tree as an antenna, you can get as much as 20 or 30 dB of antenna gain. If you were in a forest and wanted to use a modern mobile cellular telephone, you'd probably have to be within a mile of the tower, or the signal would drop below usable levels.

Nimur (talk) 20:47, 8 May 2016 (UTC)

Driest place east of the Mississippi river

Which place in the United States east of the Missisippi river receives the lowest average annual rainfall?