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November 5

Does this concept describe virtual reality, or does it describe 3-D movies?

I'm writing a sci-fi story. Here is a concept I'm describing:

"If someone wanted to visit Hawaii without leaving home, that person could still see Hawaii, but first, the person's eyes would have to be covered with two displays (one for the right eye and one for the left eye), each display showing live action moving images (one for the right eye and one for the left eye) of life, like, someone at home could be able to see, for example, Hawaiians surfing. The image of the right eye and the left eye combine to form a single image."

I don't know what my concept is an example of, though. One person told me I was describing virtual reality. Another person told me I was describing 3-D movies. I don't really know the difference between virtual reality and 3-D movies. So is my concept an example of virtual reality or 3-D movies? VRtrooper (talk) 06:28, 5 November 2015 (UTC)

Your technology (variations of which exist, I should mention, so it's not altogether sci-fi) shares elements of both 3-D displays and virtual reality. The relevant articles you are going to want to look at are Stereopsis, binocular vision, virtual reality and 3D film. In short, in normal vision, the human visual system constructs a three-dimensional representation of the surrounding environment by comparing two essentially 2D image maps formed by stimuli acting upon the retina of each eye. The thing is, the pattern recognition capabilities of the brain are such that it can extract a three-dimensional representation even from a two-dimensional projection (hence the effect of a regular television or cinema screen and numerous forms of optical illusion). 3-D movie technology attempts to augment this perception by introducing more depth to the image it projects and allowing one to adjust their angle of perception to the stimuli. This can be accomplished in numerous ways; perhaps the most common in the history of 3D-cinema is to form a 2D projection to which the color has been altered in such a way that, when the viewer wears glasses with two lenses that filter different wavelengths of light, each eye is given a somewhat different set of stimuli, even if each is focused on largely the same point in space. The effect leverages binocular vision and allows for the perception of depth from an image which actually consists of optical stimuli on a flat plane. Depending on how your headset was designed, it could leverage similar effects, though probably through different mechanisms than colour filtration. In any event, any headset displaying a visual representation of a simulated or pre-recorded environment which the user could interactively engage with would be considered a form of virtually reality, which is basically defined by that form of interactivity. Snow ^{let's rap} 06:54, 5 November 2015 (UTC)

The Stereoscope has been around for about 200 years, and a 3-D film is simply a moving-picture version of the same idea. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:14, 5 November 2015 (UTC)

• Real world devices that use this idea include the Virtual Boy, Oculus Rift and the Virtuality. Smurrayinchester 09:35, 5 November 2015 (UTC)

Or Google Cardboard and your cell phone. --Stephan Schulz (talk) 13:49, 5 November 2015 (UTC)

The difference between a 3D movie and virtual reality is that in the latter you get to decide where to go. That's why the latter is a "reality" rather than just a 3D image. I don't think that wearing a headset or using inertial sensors or even having 3D is actually a requirement of virtual reality, since people have been using the term loosely for a very long time (and hey, your virtual avatar might be a Cyclops! Come to think of it, having the people with old/simple equipment appear as cyclopes would explain their uncoordinated blundering, and just be kind of cute), but certainly some would insist on it. Wnt (talk) 13:52, 5 November 2015 (UTC)

Q: What is cyclopes' favorite reference? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:07, 5 November 2015 (UTC)

It is a fuzzy line between 3D video and true Virtual Reality. In a 3D movie (or TV), the display covers some area of a wall of the room - and appears as a "window" into a 3D virtual world. In the ideal of VR, you have a StarTrek-like "holodeck" which is indistinguishable from reality...but our present technology is far from being that good. With a typical VR headset, there is also a 'head tracker' - a device that measures where your head is pointing - the computer figures out where your head is pointing, then generates pictures that are both 3D *and* representative of the virtual world you're standing in. The effect is that no matter where you look, what you see is the virtual world. With 3D TV/Movies, when you look away from the screen, all you see is the wall of the real room that you're in. The effect can be quite convincing with very high end VR equipment - but on cheaper consumer-grade devices, it's more of a novelty than a convincingly "real" experience. Beyond that, you can add various control devices that also track the position of your hands, perhaps individual fingers even...and perhaps also your feet - so that when you look at your hands through the VR goggles, you see computer-graphics hands that are in the right place. This stepwise approach to making more and more real effects can include things like little balloons mounted into the fingers of gloves that the computer can inflate and deflate to give you a feeling of 'touch' when you grasp a virtual object...these are in no way convincing, but they allow a lot more subtle control in the virtual world. I've worked on systems that attempted to add smells and other effects such as wind blowing in your face, etc, etc. SteveBaker (talk) 02:49, 6 November 2015 (UTC)

Australian Spider Identification

Hello, I was wondering if someone could help me identify what species this spider belongs to. I do know that the photograph was taken in Darwin, Northern Territory, Australia and that it's a huntsman spider, possibly of the genus Heteropoda. Any help would be greatly appreciated.

Americanfreedom (talk) 06:56, 5 November 2015 (UTC)

I'd lean towards Holconia: [1], [2], [3], [4], [5] Snow ^{let's rap} 07:30, 5 November 2015 (UTC)

Here we go, would you like to buy him some companionship? Actually, don't; one will very likely try to eat the other, but this newest image/phenotype does seem to suggest that your specimen is likely to be a variant of Holconia immanis, or a very closely related species. Snow ^{let's rap} 08:13, 5 November 2015 (UTC)

Age of the Universe

I read that the Universe is c. 13 Billion years old, and that our Sun is c. 4.6 Billion years old. I also understand that there are Suns/Stars that are c.10 Billion years old. Considering the time taken to form suns, followed by planetary solar systems, and the time taken to form Galaxies, and that the death of a star is where (I am informed) the heavier elements are distributed, the relative lifespan of the Universe and Stars appear not to make sense. Explanation please? — Preceding unsigned comment added by 79.134.38.231 (talk) 07:29, 5 November 2015 (UTC)

The death of a star only causes heavy elements to be distributed if the star dies in a supernova explosion. The stars that undergo these explosions are very large ones. But the larger a star is, the less time it lives. The very large stars that become supernovas do not last billions of years, but much less, perhaps only 10 million years. --70.49.170.168 (talk) 07:59, 5 November 2015 (UTC)

Yep. The article Stellar population explains a bit more. The oldest star whose age is fairly certain is SM0313: at about 13 billion years old, it's nearly the same age as the universe. However, it's a "K dwarf" – fairly small and cold compared to, say, the sun. Supergiants and hypergiants, which are the really big and hot stars, only live a few million years. There have been many generations of supermassive stars blasting metals throughout the galaxy. Smurrayinchester 08:40, 5 November 2015 (UTC)

Also, since certain heavier elements catalyse fusion processes, earlier stars (in particular population III stars), which are poor in metals (in the astronomy sense), start fusion slower and at higher densities, thus allowing stars to become a lot larger before ignition, when radiation pressure clears the environment and accretion stops. Thus, population III stars are hypothesised to have been, on average, very large, and hence short-lived. --Stephan Schulz (talk) 13:47, 5 November 2015 (UTC)

If you want more details, I highly recommend Crash Course Astronomy. --71.119.131.184 (talk) 09:41, 5 November 2015 (UTC)

As per Stellar population, the idea is that early on, it was easy to form huge stars that supernovaed fast. These burst into supernovae and salted the galaxies with heavy elements. Even so, the older stars are more metal-poor than the new stars, because the process continues. Wnt (talk) 13:47, 5 November 2015 (UTC)

BTW when people here say "metal" they don't mean an actual metal, but rather any element heavier (i.e. more protons) than helium. So carbon and oxygen are "metals" in this context. Ariel. (talk) 16:46, 5 November 2015 (UTC)

estimated time to cure hepatitis A infection

OP curiousMahfuzur rahman shourov (talk) 16:18, 5 November 2015 (UTC)

See Hepatitis_A#Treatment. In short, forever. Hepatitis A cannot be cured, only its symptoms managed. --Jayron32 16:26, 5 November 2015 (UTC)

@Jayron32: That article says 1-3 weeks in children, 2-6 months in adults. Wnt (talk) 18:00, 5 November 2015 (UTC)

That's not the length of time the disease infects you, that's the time the symptoms are evident. The disease "flares up" for periods, and goes into remisssion for periods. A person is not cured of the disease merely because the symptoms have subsided for a time. --Jayron32 19:51, 5 November 2015 (UTC)

Hepatitis A is a self limiting disease that resolves on its own without any specific treatment in ~6 months. After that it is actually "cured" in sense that virus has completely disappeared from the body. The resolution results in life-long immunity. Ruslik_Zero 20:19, 5 November 2015 (UTC)

Yes, of course. I was confusing it with it's more chronic cousins, like Hepatitis C. Mea culpa. --Jayron32 20:34, 5 November 2015 (UTC)

(EC) I think Jayron2 may be getting confused with Hepatitis B and C (and perhaps some of the others). Both of these can result in chronic conditions. See Viral hepatitis and [6]. Hepatitis A does not (see the earlier refs) and nor is it a retrovirus which integrates in to the genome or have a long term latency phase (like say the varicella zoster virus). So once it's gone (which as was said may in some cases be 6 months or even a year), it's gone. Kariskwilson's point below is also relevant, there's not that much you can do to treat the symptoms or to speed up recovery beyond the basics (including those related to the symptoms like avoiding overtaxing the liver), and waiting for your own immune system to fight off the infection and body to recover from the symptoms. (As to whether to say you're "cured" this is to some extent a matter of semantics. Are you "cured" of a cold or flu? And in those cases you can I think have a greater effect on the symptoms.) Nil Einne (talk) 20:46, 5 November 2015 (UTC)

Hepatitis A can not be cured. In summary the definition of "cured" means to relieve symptoms of something in some way. The exact definition can be found at http://dictionary.reference.com/browse/cure. Also, the condition and effect of the disease can be lessened with medication and giving the body or the liver time to rest From things like medication or alcohol. sources and more information about what I have provided for you can be found on the following websites. http://www.mayoclinic.org/diseases-conditions/hepatitis-a/basics/treatment/con-20022163. there is no specific medication that can cure this disease but there are different thing that are natural things you can try and medication that will help in the healing process. The source for this information and more information I what I've written can be found at http://www.emedicinehealth.com/hepatitis_a/page7_em.htm.Kariskwilson (talk) 18:48, 5 November 2015 (UTC)

In any case, Hepatitis A can be prevented with the Hepatitis A vaccine. Get it if you can, unless you know you have immunity. --71.119.131.184 (talk) 20:34, 5 November 2015 (UTC)

Incidentally, if you've had Hepatitis A after the age of 11, you are forever after unable to donate blood (in the US and Canada, at least, and presumably elsewhere). 64.235.97.146 (talk) 21:09, 5 November 2015 (UTC)

Recovery from Hepatitis A can take anywhere from several weeks, to several months. Those most vulnerable to the infection are generally very old, sick or young. There is no specific treatment for hepatitis A and vaccines are available internationally. Jdulsky (talk) 23:27, 5 November 2015 (UTC) http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0022975/ http://www.cdc.gov/hepatitis/hav/ http://www.who.int/mediacentre/factsheets/fs328/en/

• Yes, see your healthcare provider. If you do not already have Hep A, (as well as Hep B) you can get vaccinated. The test and the vaccination were both free for me, since the insurance company would rather prevent it than deal with the sequelae. μηδείς (talk) 01:06, 6 November 2015 (UTC)

This user has been indeffed for troling

Actually the editor was blocked because they either lack the competence to edit wikipedia, or they are trolling. Nil Einne (talk) 17:33, 8 November 2015 (UTC)

Where can I get information about the the rotation degrees of the Atlas around the axis?

I've searched many articles and I didn't find. I just want to know how many degrees is ability of the atlas to rotate around the axis dent. 78.111.187.141 (talk) 17:08, 5 November 2015 (UTC)

What 'Atlas' do you mean? This or may be this? Both cam rotate around an axis. Ruslik_Zero 20:13, 5 November 2015 (UTC)

He means the biological one Ariel. (talk) 20:44, 5 November 2015 (UTC)

Finasteride mechanism.

Finasteride inhibits 5 Alpha Reductase (5 AR) which is responsible for converting Testosterone to DHT which inturn is responsible for male pattern baldness. How much 5 AR does 1 mg Finasteride inhibit ? 5 AR converts 5% of Testosterone to DHT so if we increase Testosterone through sexual indulgence, exercise etc... we will be providing more facility for increase in DHT right ? So if 1mg Finasteride reduces 5 AR by x amount then the remaining (v-x) amount of 5 AR will still convert T into DHT and the amount of T increased by some activity or the other will still produce enough DHT to attack hair follicles right ? Please do give a quantitaive explanation if possible! — Preceding unsigned comment added by 175.101.24.136 (talk) 17:31, 5 November 2015 (UTC)

It gets complicated. I was going to go through according to the IC50, but it's more complicated than that - there's a Type I 5alpha reductase and a Type II. [7] It inhibits Type II, which produces 2/3 the testosterone, 100x better than type I. So a practical dose is probably, approximately, going to block a bit under 2/3 the testosterone production. But there's some tissue specificity - same paper says the prostatic DHT drops 90% with that treatment, so apparently DHT isn't in equilibrium throughout the body. So the type II that takes it in the shorts is prostate, seminal vesicle, epidydimis, hair follicle; the type I is in scalp sebum gland, liver, muscle, brain. The IC50 according to this is 5.9 nM in prostate, 310 nM in scalp. But then there's turnover ... takes two weeks for the enzyme to recover... and note the rodent results and human are different...

In reality, this is very much going to be settled empirically, not theoretically. Whatever dose is determined to work for a particular application with tolerable side effects is what people will use. Wnt (talk) 18:17, 5 November 2015 (UTC)

You're awfully interested in male-pattern baldness. Have you actually read our article? The only lifestyle factors with a well-demonstrated link to promoting male-pattern baldness are being overweight/obese, sedentary lifestyle, and chronic stress. So avoid those, which you should do for a million other reasons anyway. I'm getting a vibe of "I'm planning to take drugs without a doctor's recommendation because I think they will prevent hair loss", which is definitely a thing you should not do. If there is something else you're trying to learn, how about just asking it straight out instead of a bunch of vague questions about testosterone and drugs and hair follices? --71.119.131.184 (talk) 20:22, 5 November 2015 (UTC)

Assume good faith - the question is just interesting. It's interesting to see transgenders talk about it - there are probably biological insights to be learned regarding their inability to regrow the lost hair or the question of whether gynecomastia can be separated from it. I'd also love to see more research into He Shou Wu, despite occasional trouble with it. Still, a good rule for human biology is Don't be the science project. Let somebody else be the science project and watch what happens. :) Wnt (talk) 22:33, 5 November 2015 (UTC)

Homoromantic Asexual Men and Chocolate Allergen?

I've known two asexual men in my life who nevertheless tended toward other men. Both were allergic to chocolate. There's no correlation, is there? Theskinnytypist (talk) 19:27, 5 November 2015 (UTC)

No. --Jayron32 19:56, 5 November 2015 (UTC)

Do you have any sources for that, or is it pure speculation ? StuRat (talk) 05:18, 6 November 2015 (UTC)

Sorry, I must have thought I was you for a second. this turns up no significant cross section of information about the two random facts noted by the OP. I can't even find anyone aside from the OP who has proposed that there could be a connection. --Jayron32 16:52, 6 November 2015 (UTC)

Absence of proof is not proof of absence (of a link), so your answer is useless. Much better answers are below. StuRat (talk) 20:48, 8 November 2015 (UTC)

There could potentially be a correlation, but correlation is not causation. Two factors being linked does not necessarily mean either causes the other. Here is a website with some amusing illustrations of this. --71.119.131.184 (talk) 22:31, 5 November 2015 (UTC)

There's almost certainly no data on this - and in biology, if you don't have the data, you really don't know the answer. I'd bet money it's coincidence, but no more than I could comfortably lose. Wnt (talk) 22:35, 5 November 2015 (UTC)

(ec)Correlation does not imply causation necessarily. However identifying that the reasoning behind an argument is flawed does not imply that the resulting conclusion is false, so according to Popper we must admit the OP's alternative bold hypotheses to scientific investigation:

• Hypothesis A: Homoromantic asexuality causes chocolate allergy.
• Hypothesis B: Chocolate allergy causes homoromantic asexuality.

More than the two samples collected by the OP will be needed to lend more confidence to A or to B than already exists in the

• null hypothesis: !A AND !B

The latter predicts that wider sampling under controlled conditions will yield a standard Cauchy distribution which is the distribution of a random variable that is the ratio of two independent standard normal variables and has the probability density function

$f(x;0,1)={\frac {1}{\pi (1+x^{2})}}.\!$

Bestfaith (talk) 22:41, 5 November 2015 (UTC)

That math is great, but the math that matters is your odds of getting a Golden Fleece Award in the improbable event you actually get a research grant to study homoromantic asexual men. I am not expecting data soon. Wnt (talk) 22:49, 5 November 2015 (UTC)

Thanks, everyone, for helping me out! :) And too bad the second commentator was anonymous, because that website was hilarious! Theskinnytypist (talk) 23:35, 5 November 2015 (UTC)

What about:

• Hypothesis C: both are caused by some as yet unknown factor? (The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 14:43, 6 November 2015 (UTC)

• There is of course Hypothesis D: there is no connection, correlation, or causation between the two at all. The null hypothesis should be the default stance for any proposition. People can propose any two random facts, like "Do more people born on Tuesday have blue eyes". Unless and until evidence is presented which would support the proposition, the null hypothesis should be the default and standard answer to the proposition, without need for further proof. --Jayron32 16:54, 6 November 2015 (UTC)

Why do feces contain more dangerous bacteria than vomit?

They have both been in the stomach and exposed to digestive bacteria so why do feces contain more? ScienceApe (talk) 22:22, 5 November 2015 (UTC)

The stomach contains few if any bacteria. Your stomach is filled with acid partly in order to kill pathogens that might come in. Only a few acid-resistant bacteria can survive the environment, one notable species being Helicobacter pylori, which causes most ulcers. Your gut flora live mostly in the large intestine. --71.119.131.184 (talk) 22:25, 5 November 2015 (UTC)

Remember that the gut is actually designed to grow bacteria (people depend on vitamins they generate). And the contents have had longer to grow bacteria, wanted or unwanted, at the far end. And the bacteria have evolved to spread via feces, not via vomiting, because usually they go out the rear. (Fecal-oral route) Wnt (talk) 22:37, 5 November 2015 (UTC)

Designed? Bazza (talk) 16:38, 6 November 2015 (UTC)

Well, maybe this guy turned me into an anti-evolutionist yesterday. Or maybe the smart money is on trying to purge incorrect ways of speaking in preparation for a Ben Carson presidency. But honestly, my call is that something can be "designed" by an AI, which is not a conscious process, so why not by evolution? And really, we can't actually say that conscious thought doesn't use an evolution-like process in designing something. Wnt (talk) 12:49, 7 November 2015 (UTC)

November 6

Is it possible to say that one dimensional is one axis?

Is it possible to say that one dimensional is one axis? (doesn't matter if it's X,Y,Z). if it's right, how can it be, here is also there are length and width. I don't understand it and I would like to get explanation about it.78.111.187.209 (talk) 01:35, 6 November 2015 (UTC)

Yes, you can say that. One Dimension, is One Axis. When you have two dimensions, you also have two axes. They go together. Explain more about what you don't understand. Ariel. (talk) 02:09, 6 November 2015 (UTC)

You can say anything you want, but if you have an axis, you must have a rotation. You need at least two dimensions for a rotation to work... In two dimensions, an axis would be a point. In three it's a line. In one it's... impossible. --Jayron32 02:53, 6 November 2015 (UTC)

I think Jayron32 is using the word "axis" to mean "an axis of rotation," while Ariel is using it to mean a geometric representation of a basis vector. There are many usages of the word "axis" in mathematics and other disciplines; it is not clear to which the original question is referring. Nimur (talk) 03:13, 6 November 2015 (UTC)

Sorry yes. Brain no makee the smart thots. I go sleepy now. be better tomorrow. --Jayron32 03:39, 6 November 2015 (UTC)

Ariel, I simply want to ask this question, and you answered me about. Thank you! 78.111.186.226 (talk) 02:43, 7 November 2015 (UTC)

Neutrino blackbody radiation

Suppose I have an immense number of slow neutrinos is a huge ball in space, so many neutrinos in one place that interactions are frequent, but not energetic enough to escape the gravity of this neutrino [not neutron] star. Does that star have a temperature? Is so, what happens to blackbody radiation? If I drop some matter into this star it seems to me it would transfer some heat energy between itself and the neutrinos. Is this star opaque or transparent to light? Are W bosons able to interact with photons? Would that be enough to give it blackbody radiation? Ariel. (talk) 02:04, 6 November 2015 (UTC)

You present an interesting scenario. Neutrinos are not believed to interact electromagnetically, so they do not emit or absorb light. So the "star" would be transparent. Light is the electromagnetic interaction. And this is easy to demonstrate: Look Around You! Trillions of neutrinos are blasting through you every second, but you don't see them. They're constantly being produced by the fusion reactions in the Sun. And the neutrino flux doesn't change with time of day, since neutrinos just go right through the Earth. As for the W and Z bosons, if I'm understanding the article correctly, the W bosons interact electromagnetically but the Z doesn't. But, these bosons' half-lives are so incredibly short that I'm pretty sure you'd never notice any macroscopic effect. They're more massive than iron atoms! Now I'd like to think about your scenario a little more. Neutrinos have such a tiny mass that I'm not sure they'd have any appreciable gravitational interaction. If I'm right, they wouldn't be in a bound state, so it wouldn't really be a star, just a big unbound cloud. But I'm not a physicist so I could certainly be wrong about this. And I'm not sure if taking general relativity into account changes anything. --71.119.131.184 (talk) 03:22, 6 November 2015 (UTC)

A gravitationally bound cloud of neutrinos is possible in principle. It would be similar to an ideal gas or a photon gas (photons also barely interact with each other), and it would likewise have a temperature. Neutrinos do interact with photons (via charged virtual particles) but extremely weakly. I don't know if it would be possible to pack neutrinos densely enough to be opaque without their collapsing into a black hole. A blackbody by definition absorbs all incoming radiation. An opaque neutrino cloud (if such a thing is possible) would be a blackbody and would radiate according to the Stefan–Boltzmann law, but an almost transparent neutrino cloud would emit almost no light. -- BenRG (talk) 06:02, 6 November 2015 (UTC)

Cosmic neutrino background and Neutrino decoupling may be of interest. --Wrongfilter (talk) 07:30, 6 November 2015 (UTC)

Interesting thought experiment though not sure that neutrinos could be bound by their own gravitational force. To wit, the supermassive black hole at the center of the Milky Way seems to be emitting neutrinos. It's not unreasonable to speculate a consequence of gravity is neutrino/anti-neutrino production. That kind of makes it look like neutrinos would work like anti-gravity which is another weird thought experiment. It would be kind of satisfying if dark matter were neutrinos trying to spread out gravity. --DHeyward (talk) 15:43, 6 November 2015 (UTC)

I found this one but it describes production during shock waves, high energy events ... not antigravity :) Wnt (talk) 16:49, 6 November 2015 (UTC)

That's the what makes it weird. A condensing cloud of low energy neutrinos due to gravity creates black hole and starts emitting high energy neutrinos. That's kind of a backlash against gravity. "anti-gravity" if you will as it evaporates. Probably a whole slew of laws would need rewriting. --DHeyward (talk) 21:59, 6 November 2015 (UTC)

@DHeyward: It doesn't seem any more counterintuitive than solar wind or supernova, or (especially) those crazy stellar jets that shoot away from stars. Wnt (talk) 13:03, 7 November 2015 (UTC)

Black holes are perfect blackbodies, absorbing all incoming matter, and they likewise emit all types of matter as blackbody radiation, including neutrinos. It has nothing to do with "anti-gravity" or "neutrinos trying to spread out gravity". -- BenRG (talk) 00:24, 7 November 2015 (UTC)

Ben, a gravitationally confined set of low energy neutrinos that condenses under it's own gravity is nothing observed. Neutrino radiation from blackholes is also not well understand nor predicted. Surely you see the paradox of condensing neutrinos beyond the black hole event horizon. --DHeyward (talk) 06:49, 7 November 2015 (UTC)

You're talking about something that has occasionally been studied as a "neutrino star" -- just a big ball of neutrinos bound under their own gravity. (Be careful, though; "neutrino star" can have other meanings.) This type of object actually cannot be very dense at all because of degeneracy pressure, which creates a kind of hydrodynamics even though the neutrinos are almost completely non-interacting. The problem is that the neutrino mass is so small, the neutrinos have to have an extremely tiny energy to stay gravitationally bound. This means there are only a few states for them to occupy within a finite volume, and because the neutrinos are fermions, there can only be one of them per state. It just isn't possible to pack any more in without giving them a higher energy, in which case they would free stream away. Such a neutrino star would therefore be an enormous, very diffuse object. Not only would it be transparent to light, you wouldn't notice at all if you were in the middle of one. --Amble (talk) 08:41, 7 November 2015 (UTC)

Hmmm, here's a ref. Wnt (talk) 12:43, 7 November 2015 (UTC)

Yes, that's one example, but note that they're not talking about neutrinos as we know them. Instead, they're talking about a star made from a hypothetical and unknown additional neutrino species with much greater mass than the standard model neutrinos. This sort of thing was very interesting back in the 1990's when people thought there might be a 17 keV neutrino (although that turned out to be wrong). Since then, it requires a sterile neutrino or some other new neutrino-like particle with a large enough mass that you can build a compact object; that's what makes it a "heavy neutrino" star. With the very light neutrinos we know about, the density ends up being ridiculously tiny. --Amble (talk) 17:24, 7 November 2015 (UTC)

Here's another paper assuming a 3 eV neutrino [8]. This was on the heavy end of possible standard model neutrino masses, but it's ruled out now. They were talking about galaxy-sized neutrino "stars" in the center of galaxy clusters. --Amble

brain vs computer damage

I understand that depriving someone of oxygen will cause unconsciousness, but why does it cause permanent brain damage?

After all, if you unplug a computer, its battery will run out, but it won't suffer permanent damage. 203.45.134.227 (talk) 04:25, 6 November 2015 (UTC)

The brain starts to die, because without oxygen your brain cells can't produce enough energy to stay alive. See hypoxia (medical) and cerebral hypoxia. The brain is very energy-hungry (an adult human's brain accounts for about 25% of the body's energy demands), so the brain is very sensitive to oxygen deprivation. To examine your analogy, our brains don't have any permanent storage akin to a hard drive or flash memory, that stays as-is without using energy. Living cells constantly need to expend energy. In the vein of your computer analogy, you could say the brain is all CPU and RAM. And to be a little pedantic, computers can suffer damage from loss of power. If nothing else you lose any data that hasn't been written to permanent storage. This can be especially bad if it leaves the file system in an inconsistent state. Ever seen a message telling you not to shut off your computer, like while installing operating system updates? Modern file systems use techniques like journaling and copy-on-write to make catastrophic file system corruption less likely. And, hard drives these days tend to be more fault-tolerant, but in years past it wasn't unheard of for hard drives to be physically damaged or destroyed from a head crash after a sudden power loss. --71.119.131.184 (talk) 04:46, 6 November 2015 (UTC)

Good description. I would add that most machines are designed to be able to be shut completely off, but complex animals can't do this and survive. The closest complex animals come is hibernation and hypothermia. Plants and some simple animals seem more able to go dormant for long periods. There's seeds and bulbs in the case of plants, and some insects and spiders may be able to do something similar. StuRat (talk) 05:27, 6 November 2015 (UTC)

It isn't only simple animals; some mammals can survive long periods of hibernation at very cold temperatures: The Arctic ground squirrel can survive conditions where its internal body temperature is below the freezing point of water (the body itself doesn't freeze solid because the body isn't pure water, it's pretty salty, see Freezing-point depression) --Jayron32 13:26, 6 November 2015 (UTC)

Hibernation isn't the same as a machine being shut off, as metabolic activity continues, just at a slower rate. It's more akin to an idling machine. StuRat (talk) 20:51, 8 November 2015 (UTC)

Apoptosis is a frequent contributor to brain injury, and often it seems like the death really doesn't "need" to happen. See [9] for information, including various ways in which some of the damage can be prevented. As I recall xenon stood out - even if given after the injury. But necrosis is a feature of some of the damage, so it's not like there's a magic bullet in that regard. Wnt (talk) 10:10, 6 November 2015 (UTC)

Weak points in/of a human body

I wish to learn about all the weak point(s) in/of a human body; from head to toe. Does anybody know? Illustrations with summaries would be helpful. -- Space Ghost (talk) 10:11, 6 November 2015 (UTC)

I think we'd need a better pointer as to what you want to know. For instance hair is fairly strong when pulled but pretty weak if you push two ends towards each other or if you bend it. And I believe it is stronger when pulled than a fiber of nylon but weaker than a thin wire of good steel. I think my brain would be pretty weak if taken out and poked too. Dmcq (talk) 10:39, 6 November 2015 (UTC)

(edit conflict) Assuming that you mean "weak points" in respect of physical assault rather than infection, in Japanese martial arts (particularly Ju-jutsu and Judo), attacking these points is called atemi waza ("striking techniques"). See Atemi-Waza - Vital Point Striking for details. Alansplodge (talk) 10:42, 6 November 2015 (UTC)

Saw the pictures . Thank you! -- Space Ghost (talk) 18:46, 6 November 2015 (UTC)

Where can you find whole grains?

Commercial bread contains carcinogenic preservatives or is very expensive and not very tasty. Rice is full of arsenic. You can eat only so much whole-grain pasta. 69.22.242.15 (talk) 11:49, 6 November 2015 (UTC)

Grow your own wheat, rice, and pasta? 140.254.136.179 (talk) 13:16, 6 November 2015 (UTC)

Here are a few articles on choosing good whole grain products: [10] [11]. --Jayron32 13:22, 6 November 2015 (UTC)

Not sure you will escape periodic table. It's true that industry can concentrate certain bad things in areas where they weren't concentrated before but many places have natural background variations of carcinogens that simply exist. "Natural spring water" for example can exceed EPA safe limits for many elements without ever being touched by humans. Lead, arsenic, mercury, uranium etc, etc, all exist naturally and often near water sources necessary for agriculture. But why "Whole grains?" Humans don't seem particularly suited to eat whole grains without processing of some type and became dietary for economic reasons. We seem more naturally suited to eat fruits, vegetables and vertebrates. --DHeyward (talk) 16:01, 6 November 2015 (UTC)

Whole grains contain higher amount of dietary fiber; its indigestibility IS its main positive trait. Also, whole grains contain bran, which besides the dietary fiber contains other nutrients not available in more processed grains; the processing can remove these nutrients, and lower the amount of dietary fiber. --Jayron32 16:09, 6 November 2015 (UTC)

I agree with Dheyward, that humans have only recently started eating grains, on an evolutionary scale, and thus haven't fully evolved to digest grains. Whole grains, for example, can be indigestible. While this provides fiber, so do many vegetables, and with better nutrients. Cracking whole grains make them a bit more digestible, as does rolling oats. As for avoiding preservatives, then you need to eat the whole grains quickly. Also, the fat in the grains will go rancid. An alternative is to make "breads" from nut flours, such as almond flour, which are more nutritious, but also need to be eaten quickly. StuRat (talk) 21:02, 8 November 2015 (UTC)

Humans have been eating grains for at least tens of thousands of years. And grains are just seeds, which are widely consumed by many animals. --71.119.131.184 (talk) 03:31, 9 November 2015 (UTC)

Yes, and tens of thousands of years isn't much time on an evolutionary scale, at least for a species with some 20-30 years between generations. Other animals that eat seeds or grains have major adaptations, such as gizzards. StuRat (talk) 05:45, 9 November 2015 (UTC)

Many things are carcinogenic, including oxygen and ethanol. Just saying something is carcinogenic is effectively meaningless. I am not aware of any scientific evidence that the preservatives used in most foods are a health concern at the levels used. --71.119.131.184 (talk) 06:44, 7 November 2015 (UTC)

STD Transmission

Why do health educators say that abstinence provides 100% protection and at the same time they say that, even if a person does not engage in sexual activities, has never had sexual contact or a kiss on the lips, has never had organ transplant or blood transfusion, has not shared needles with others, has no congenital STDs, has never shared clothing, etc., as having a very low risk of STD? "A very low risk of STD" is not 100%, which implies that even if a person is abstinent all his life, he may still have an STD out of the blue or some kind of occupational needle-stick injury? I notice that if pathogens can be transmitted by aerosol or water or food, then somehow it is not considered an STD? If those are not considered STDs, what is the reason behind the "very low risk" as opposed to saying "no risk at all unless you have a freak accident or an occupational needlestick injury"? 140.254.136.179 (talk) 13:45, 6 November 2015 (UTC)

Could you provide a source where a medical professional or professional body or health educator has stated that there is a low risk of an STD for a non-sexually active person?--Phil Holmes (talk) 14:00, 6 November 2015 (UTC)

Few babies are sexually active, but may get an STD from their mother either in utero or during the birth process. See vertically transmitted infection and HIV and pregnancy. So, obviously, you can get STDs through non-sexual means. Abstinence is only considered 100% effective if you're only considering STDs that are literally being transmitted during sex - sexual abstinence would not stop you from getting HIV from a dirty needle either. 64.235.97.146 (talk) 14:33, 6 November 2015 (UTC)

For one thing, you can kiss even if you are abstinent. Kissing carries a non-zero risk of transmitting disease. Second, STDs are "infections that are commonly spread by sex" (italics by me) as our article Sexually transmitted infection says. It's still called that even if it's transmitted in a non-sexual way, much like the common cold doesn't become an STD if somebody gets it through sexual contact.

Phil, CDC says that abstinence protects against STDs. I don't think anyone questions that the risk generally is low for non-sexually active adults (with exceptions, such as IV drug users). Sjö (talk) 14:40, 6 November 2015 (UTC)

I think this is one of those self evident things that gets blown out of proportion. If you never commit any activity which could ever bring you into contact with those infectious agents, you never get the infectious agents. Of course, the discussion over passing STIs via non-sexual contact is a different discussion, but lets put that aside for a second. If (I know this is never true, but pretend it is true for the discussion), If a specific disease is ONLY passed on through sexual relations, then if a person never has sexual relations, the NEVER get the disease. That's how concepts like "ONLY" and "NEVER" work. In logic, this is called the Logical conjunction: A person can become infected only if a) they have sexual contact with b) a person who is themselves infected. Since a person only has complete knowledge of option (a) (whether or not they have sexual contact), that's the only thing they have control over. The actual discussion over whether or not that is true as to whether STIs can be passed by non-sexual contact is not relevant to the message being delievered for the purpose being delivered. From a public health standpoint, reducing preventable infections is a basic goal. If the message "If you don't have sex, you don't get infected" reduces infections by stopping people from having risky sex, that's why its stated that way; it's also accurate enough, at least within significant figures when comparing the infection rates of people who get STIs from non-sexual sources, that is while the numbers are not zero, the numbers are both a) low enough that they don't much affect the overall percentage of total STIs and 2) not readily preventable by behavioral modification. This article mentions non-sexual transmission methods, but does not go into statistical details. It does, however, contain links to articles which do. This article notes that the risk of catching HPV infections outside of sexual intercourse is about 11.6%, much higher than most STIs, but that still means eliminating sexual activity reduces your risk of catching it by an order of magnitude. this rather long article also has some information on infection rates and infection pathways for various STIs. --Jayron32 14:57, 6 November 2015 (UTC)

(EC) I'm not sure Phil is questioning the risk is low. I think Phil is querying whether health authorities say the risk is low instead of saying there is no risk. But as you said, the risk is low is the correct assessment. I would also note that I don't think many health authorities refer to someone who "has never shared clothing, etc" anyway. Probably even the kissing on lips doesn't generally come up. Nil Einne (talk) 15:01, 6 November 2015 (UTC)

Indeed, as I mentioned (and just to clarify the thesis, just because it may get lost) the issue is "Where is the message coming from and for what purpose." Since the message is coming from public health officials, the purpose is to reduce rates of infections. Public health officials have identified sexual behavior as a major vector for these diseases, and are making statements to alter behavior so as to lower transmission rates. There's a difference here between statements made by public health officials who are trying to get people to change behavior, and research scientists who are trying to find verifiable statistics. While the latter certainly informs the former, the actual statements they make have different purposes. --Jayron32 15:08, 6 November 2015 (UTC)

There's always something. Dentists who don't clean their equipment. Tattoo parlors. Getting shot and the bullet goes through someone with HIV on its way to you. (Well, honestly, I don't know if that one works :) ) Sharp edge on a railing. There's always something... you have to be creative to come up with a whole list of ideas, but nature is more creative than that. Wnt (talk) 16:54, 6 November 2015 (UTC)

You may have been thinking of Legrand G. Capers' claim that a woman had become pregnant during the american civil war by a bullet that passed through the body of a man and into her, however, that turns out to have been untrue. SteveBaker (talk) 15:22, 7 November 2015 (UTC)

I hadn't heard that one. But transfer of intact sperm cells is clearly going to be more difficult than transfer of viral particles. (There's no guarantee you can do either, though - my main concern would actually be the immense heat and air exposure of the bullet, which might well sterilize any adherent fluid) Wnt (talk) 01:42, 8 November 2015 (UTC)

There's a factor that nobody has mentioned yet. Health authorities do not know a person's sexual activity history, and are obliged to record what the person tells them about it. If the person lies and says they have never had any form of sexual relations, nobody can challenge that, so 'low risk' gets ticked in the Total Abstinence column when there's really a distortion of data taking place. Akld guy (talk) 05:30, 7 November 2015 (UTC)

Adoption of abstinence as a method of preventing transmission of sexually transmitted diseases fails when sexual activity takes place. Therefore, the adoption of abstinence has a failure rate, and there is a non-zero risk for sexually transmitted diseases if you adopt abstinence. It's the same principle that failures of comdom use as method of contraception gets counted against condom use even if the reason for the failure was "forgot my condom". - Nunh-huh 02:06, 9 November 2015 (UTC)

Abstinence is 100 percent safe. If sexual activity takes place, it is no longer abstinence. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:00, 9 November 2015 (UTC)

You forgot to put your joke in small text. At least I suppose that it is a joke as even skimming the section will tell you that abstinence isn't a 100 % protection against STDs. Sjö (talk) 12:17, 9 November 2015 (UTC)

List of tallest elevators?

Hello Wikipedia Reference Desk:

I am looking for a list of the world's tallest elevators. I have only been able to find our list of tallest buildings in the world; but most of these buildings have complex elevator systems; it is not generally true that the taller buildings have taller individual elevator shafts. Furthermore, there are a handful of sophisticated elevators in the mining industry, freight transport, and other more esoteric applications that dwarf the elevators of many modern skyscrapers.

Is this eclectic information organized anywhere on Wikipedia, or should I start engaging with the folks at Talk:Elevator?

(I am aware that Shanghai Tower reputedly contains the tallest - rather, the furthest-travel - at some 580 meters... I'm looking to qualify and compare that factoid in context).

Nimur (talk) 15:32, 6 November 2015 (UTC)

This looks like it has some promising leads. It led me to This which claims to have information on the tallest elevators on Earth. --Jayron32 15:40, 6 November 2015 (UTC)

wow. I was surprised modern elevators still use cables. --DHeyward (talk) 22:10, 6 November 2015 (UTC)

What did you think they used? --71.119.131.184 (talk) 06:37, 7 November 2015 (UTC)

There are hydraulic elevators - which are common in buildings about 4 stories and less, others that use gear wheels to climb a toothed 'rack'...check out Elevator#Types_of_hoist_mechanisms for several alternatives to cables. SteveBaker (talk) 15:15, 7 November 2015 (UTC)

Do chemists tend to memorize solubility guidelines?

The textbook I have says "Unfortunately, there are no rules based on simple physical properties such as ionic charge to guide us in predicting whether a particular ionic compound will be soluble or not." and there is a table of soluble ionic compounds with lines such as "chlorides, bromides, and iodides are soluble except in compounds with Ag+, Hg2+, and Pb2+" and "sulfates are soluble except in compounds with Sr2+, Ba2+, Hg2+, and Pb2+". There is another table of insoluble compounds with a list of exceptions, but you get the point. Is this information generally memorized by most people whose job title includes the word "chemist"? 20.137.7.64 (talk) 18:19, 6 November 2015 (UTC)

I don't think they have to pass an exam about it, but compounds like silver chloride, mercury iodide and strontium sulfate are entities that people who are even not officially chemists start to become familiar with. Wnt (talk) 20:33, 6 November 2015 (UTC)

Yes, chemists know those general guidelines. Every chemist I know knows the basic solubility rules. Of course, if chemists really want to know solubility in a quantitative way (that is, the exact solubility of a substance at a given set of conditions) they look it up somewhere. The solubility rules are really a heuristic taught to high school and first-year college chemistry students to remember which ionic compounds tend to be soluble, and which tend to not be, based on general patterns and trends. As soon as someone is on the path towards being a professional chemist, they learn the more detailed aspects of solubility (such as the role of Coulomb's law, the details of solute-solvent interactions, solubility product, etc. etc.) Just like you can still sing the "ABC song" even though you probably were taught it as a child, Chemists would still all pretty much know and understand that all halide salts except silver, mercury, or lead are fairly water soluble, and similar guidelines. The main utility of those rules, for what it's worth, is not in actually making solutions from first principles, like dumping solids into water and stirring them until they dissolve. The purpose of learning those guidelines is to be able to predict the results of precipitation reactions. In simplest terms, YES every chemist knows those rules, because they all learned them as a step along the way of their education. Many chemists would use more quantitative calculations and principles (like solubility product) on their actual jobs, but they don't undergo some elaborate "memory erasing" technique to forget their high school chemistry classes. --Jayron32 21:23, 6 November 2015 (UTC)

Thanks. (OP, different IP) I was pretty much wondering if this table's worth of information was worth expending the effort to hard commit to memory. 75.75.42.89 (talk) 22:26, 6 November 2015 (UTC)

Has anyone ever installed a swimming pool on an aircraft?

Has there ever been a plane with a swimming pool on board? I mean a working plane that can still fly, and a pool big enough to actually swim a little before you hit the other end. I've heard of jacuzzis on private jets, and the Evergreen Museum Waterpark in Oregon that has water slides built through a retired 747, but not an actual airborne pool. 94.12.76.44 (talk) 20:30, 6 November 2015 (UTC)

I'm thinking [12] which gets " the U.S. Forest Service will get 22 military aircraft — seven HC-130H Hercules air tankers and 15 C-23B Sherpa cargo planes ". Whether a tank is a swimming pool is kind of subjective... because airlines change attitude, the notion of one surrounded by a nice flat tile area to sunbathe on is problematic! Looks like Lockheed HC-130 and Short C-23 Sherpa are the articles for those. The former holds 45,000 kg = 45,000 liters; the latter is only a tenth that according to the articles. So think 20 dm x 20 dm x 115 dm = 2 m x 2 m x 11.5 m, I think, assuming nothing else on board? That's a fair swim lane, I suppose... Wnt (talk) 20:42, 6 November 2015 (UTC)

Thanks! Hadn't thought of firefighting planes, but now that you mentioned them it reminds me of the old story about the scuba diver caught in a water scoop[13]... luckily not true! 94.12.76.44 (talk) 20:50, 6 November 2015 (UTC)

It would be difficult to do this safely (for an actually swimmable pool), because the water would be subject to the free surface effect. The normal mitigations to this (breaking the volume up into multiple compartments, or having baffles or honeycombing inside the tanks) wouldn't be viable for a pool (I guess one could have a pool where the baffles were removed when the aircraft was on the ground - but that seems like even more work). I can't find much info about the tankage of firefighting airtankers, but this patent for the Bombardier 415 talks about baffling for its tanks (i.e. it's not one big volume of free water). -- Finlay McWalterᚠTalk 21:04, 6 November 2015 (UTC)

• I don't believe it has been done yet. This article notes that a Saudi Prince once asked Airbus to install one on his airplane, and they flatly refused. Several other sources note that it's never happened before; there's been rumors, but no one has ever actually built a full-fledged swimming pool on any airplane. The closest I could find was this article which notes that the Airbus Beluga is big enough to house one, but not that anyone actually ever installed one. --Jayron32 21:13, 6 November 2015 (UTC)

Thanks both. If someone basically richer than God asked Airbus directly and they said it can't be done, I guess that answers my question. But does it take a certain minimum volume of water for the free surface effect to be significant, or could it build to a dangerous level even in a large jacuzzi? If jacuzzis deal with it by really fast drainage controlled from the flight deck, presumably that could work for a bigger pool too if it had enough pumps. 94.12.76.44 (talk) 21:51, 6 November 2015 (UTC)

The problem is oscillation of a relative mass. Even fire trucks and milk trucks and fuel trucks have baffles. Multiple, small jacuzzis is fine. A pool with jets to simulate a lap pool is fine. But even the fuel tanks in large aircraft are baffled so that sloshing doesn't alter the center of gravity in any way that makes it close to observable (let alone unstable). I believe Jet A is about 7 lbs per gallon while water is 8 lbs per gallon. They can deal with the weight but likely not such a large, unbaffled structure as a pool. A Swim spa is fine. --DHeyward (talk) 07:50, 7 November 2015 (UTC)

For greater clarity: by "gallon", D. means a gallon, not a gallon, which would weigh 10 pounds. --70.49.170.168 (talk) 09:05, 7 November 2015 (UTC)

November 7

I will be correct if I say that the definition of “dimension” is “something that we can measure” ?

Will I be correct if I say that when we say “dimension” it means “something that we can measure”? (in oxford dictionary is written “A measurable extent of a particular kind, such as length, breadth, depth, or height”, but it's important for me to know the answer to the other definition) 78.111.186.226 (talk) 02:47, 7 November 2015 (UTC)

It originally meant "a measuring out".[14] It has become specialized to mean other things, like "a component of a situation", or in geometry, an object with "length, width, height" etc. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:01, 7 November 2015 (UTC)

Thank you for you answer, but I really didn't understand the answer for my question. (If the represented definition is considered as correct or no) 78.111.186.226 (talk) 06:18, 7 November 2015 (UTC)

You don't say in what context you are using the word. The OED has the geometrical definition "A mode of linear measurement, magnitude, or extension, in a particular direction; usually as co-existing with similar measurements or extensions in other directions.", but you have asked the question at the science desk, so perhaps you want Joseph Fourier's definition in Théorie anal. de la Chaleur (1822): "The power to which any one of the fundamental quantities or units is raised in the expression defining a derived quantity or unit in terms of them; also (in pl.), all the fundamental quantities in such an expression, each raised to its appropriate power, which together show how the unit of the derived quantity depends on the fundamental units; method of dimensions, dimensional analysis". The OED adds: "The ‘fundamental quantities’ are usually taken to be mass, length, and time, with the addition of one or more other quantities in certain cases (such as electrical and magnetic phenomena)". If you want a very simple definition for basic science, then your “something that we can measure” serves your purpose well. Dbfirs 08:18, 7 November 2015 (UTC)

The definition (in science & mathematics) is rather subtle. We talk about space as having "three dimensions" with time being a fourth dimension - but it's a bit more subtle than the concept of space having an X, a Y and a Z "dimension" because we're trying to describe a deeper "three-ness" of space. You could, for example, define a position in space by two angles and a scalar distance along that direction (polar coordinates) instead of X,Y and Z...there is nothing fundamental about there being three orthogonal distance axes. We routinely describe positions on our planet by latitude, longitude and altitude - but there are still three independent numbers used in the description. You could also describe a position by distances from three fixed points. But you soon find out that you always need exactly three numbers to specify a point uniquely. You never need four numbers and two is never enough. So the concept that space has "three dimensions" is somehow independent of how you choose to measure positions within that space. This deeper concept of "dimensionality" is somehow more fundamental than specific measurements.

We can also think of other weird and wonderful "spaces". As a computer graphics guy, I'm often thinking in "Color space" - which is similarly three-dimensional (Red, Green and Blue - or Hue, Saturation and Value - are commonly chosen axes). It's sometimes possible to solve problems by treating other quantities such as mass or electrical charge as if they were "dimensions" and to explore concepts such as mass/time/pressure/temperature as a four dimensional space. This leads us into concepts such as Dimensional analysis in which measurements of properties such as mass and charge are considered independent "dimensions". Then there are ideas like phase space where there are insane numbers of dimensions. SteveBaker (talk) 15:05, 7 November 2015 (UTC)

Basebull Bugs, according to what I got from you, I can say that Dimension is every type of measuring such length, width, depth, time and so on. Do I understand you well? 78.111.186.167 (talk) 00:46, 8 November 2015 (UTC)

Question about bees

Hello,

Can you tell me what articles would best provide me information on the decline of honeybee populations in recent years? — Preceding unsigned comment added by 2602:306:314C:CC80:87F:DF39:2EB1:F6F4 (talk) 05:58, 7 November 2015 (UTC)

If you mean wikipedia articles, see Colony collapse disorder and perhaps Pollinator decline. There are a bunch of related sub articles which will be linked from there e.g. Pesticide toxicity to bees, Imidacloprid effects on bee population, Bees and toxic chemicals, Diseases of the honey bee. Nil Einne (talk) 06:37, 7 November 2015 (UTC)

If you mean "Wikipedia articles", colony collapse disorder is the main article. --71.119.131.184 (talk) 06:36, 7 November 2015 (UTC)

Neonicotinoid#Decline_in_bee_population has some timely info and refs as well. SemanticMantis (talk) 23:00, 7 November 2015 (UTC)

What is the difference between axis and vector?

I'm trying to understand the main difference between them. Is the difference that the vector has a direction while an axis doesn't have? 78.111.186.226 (talk) 06:20, 7 November 2015 (UTC)

Without an example or reference, I would presume the difference is magnitude. A vector has a defined magnitude while an axis can be infinite. From Despicable Me, we know the nerd name "Victor" was replaced by "Vector" because his crimes had both Direction and Magnitude. Axis have direction but the magnitude is indeterminate. The units are immaterial so an X axis of force has the direction component, but in can support multiple vectors of varying magnitude. Superposition can determine the final vector on an axis but the axis is really only a direction (a scalar). --DHeyward (talk) 07:39, 7 November 2015 (UTC)

They are entirely different things. An axis is defined with respect to a coordinate system -- it is a set of points all of whose coordinates except one are zero. A vector is an entity that has magnitude and direction -- the exact definition varies according to context, but none of the widely used definitions give you anything resembling an axis. Looie496 (talk) 13:23, 7 November 2015 (UTC)

I disagree with Looie's definition of an "axis" - for example, I might talk about the "axis of rotation" of a spinning body or an "axis of symmetry" - in which case the axis has a position and a direction - but no magnitude. In the case where we're discussing one of the axes of a graph, then that Looie's definition happens to work - but it's not true for other uses of the word in physics and mathematics. I agree with DHeyward that the difference between a vector and an axis is that a vector has magnitude and an axis is presumed to be infinite in extent. Both need a position and a direction. However, people often talk about an "infinite vector" which fits the definition of an "axis" too. SteveBaker (talk) 14:47, 7 November 2015 (UTC)

You are right. I'm so sorry for that. I meant to the axis of anatomical plan. 16:06, 7 November 2015 (UTC) — Preceding unsigned comment added by 78.111.186.3 (talk)

Transformer Core Lamination Thickness

What would be an ideal thickness of a lamination used for stacking the core of a 50HZ 1kVA transformer? Is there any rule or formula which can be used to determine the thickness or number of laminations that a core will be split into in order to reduce eddy current losses?--Adenola87 (talk) 09:35, 7 November 2015 (UTC)

It is more of a cost cosideration. Thiner the better but more the cost. This explains the math:

[15] Page 42. You might notice too that US made transformers, although certified as OK on European voltages, never the less run hot. The US main frqueetcy is 20% higher than in the US so are less efficent. Thus, the greater losses producing more heat. So the best thinness is a trade off according to the application.--Aspro (talk) 14:40, 7 November 2015 (UTC)

@Aspro:, you will probably want to clarify your last statement. μηδείς (talk) 17:30, 7 November 2015 (UTC)

The last statement is explained in the reference. The one before is reinforced here [16]--Aspro (talk) 18:18, 7 November 2015 (UTC)

I was referring to "The US main frqueetcy is 20% higher than in the US" which is an apparent contradiction. μηδείς (talk) 21:31, 7 November 2015 (UTC)

It's 20% higher than in the UK, of course (60Hz vs. 50Hz.) Dbfirs 21:35, 7 November 2015 (UTC)

"Laminations for small power transformers are generally 0.014 inch thick; thicker laminations up to 0.025 inch are occasionally used, but result in increased losses..." - page 235, Radiotron Designer's Handbook, Fourth Edition, 1952, which is available online as a free PDF download. I would think a 1 kVA power transformer would fall into the 'small' class. Therefore, the thickness of your laminations ought to be in the vicinity of 0.015 inch. Akld guy (talk) 02:11, 8 November 2015 (UTC)

I just opened-up a a burnt-out transformer from an old AVR and measured the thickness of the laminations. Yes, @Akld guy you are right, it is just within the range you mentioned. I am currently working on a special project I appreciate the help that I am getting here. Thanks.--Adenola87 (talk) 10:14, 9 November 2015 (UTC)

Chairlift height and accidents

How high to the ground (not the altitude) can a chairlift go? Has anyone been forgotten in one and died because he couldn't get down? This is the plot of Frozen (2010 American film), which is unrealistic, but I wonder how accidents in chairlifts happen. The corresponding article does not have any reference of deadly accidents. Denidi (talk) 14:32, 7 November 2015 (UTC)

Close; I found Money-burning snowboarder rescued from Alpine ski lift. He was trapped 10m up when the ski lift shut down for the night and was only found 6 hours later when he burned 120 euros of banknotes to attract attention. Alansplodge (talk) 01:35, 8 November 2015 (UTC)

In researching this, I did find [17] which claims a death in the short lived Charlotte Pass to Thredbo ski lift in Australia, but it doesn't seem very confident and I couldn't find more info because a lot of sources are discussing how the lift was dangerous due to the risk of death from exposure and inaccessbility of the terrain meaning rescues were difficult.

I suspect deaths from being left behind are less common than death from falling or not offloading safely, or maybe also some cases off being stuck somehow and fatally injured; whether due to operator error, user error or defective lifts. E.g. [18] [19] [20] [21] [22] [23] suggests deaths from falling are uncommon in the US, but they do happen. Note the statistics on deaths only refer to cases of defective lifts, although I guess you may wonder whether cases where someone has a medical emergency on a ski lift which is why they fall like [24] [25] should be called a death from a skilift. [26] [27]is a case of being stuck and tangeled in a backpack and strangled, in the French Alps. [28] a death from a fall in it Italy. [29] in the Swiss alps is a death from falling. [30] is interesting, a death from falling but only after not dismounting at the right time, also in the Swiss alps. Not sure whether you'll consider them ski lifts but [31] mentions two deaths on a Surface lift#Magic carpet. There are also case like [32] where someone is killed perfoming maintenence ([33] has a case where someone lost both legs). There are also cases like [34] where some hits a lift tower, but I guess most wouldn't consider them deaths due to ski lift accidents. [35] has some general comments on safety in the US.

Nil Einne (talk) 02:58, 8 November 2015 (UTC)

Whoops somehow I missed that you said chairlift rather than skilift, sorry. I think even discounting the Magic carpet case, some of those were ski lifts of some sort but not chair lift. I'm lazy to check each one and I'm not sure if the sources I provided always specify. Since you did mention chair lift, there is a disputed claim of a death on the former Skylink chair lift at Dreamworld in Australia here [36], but while I'm fairly confused about what other thread is being referred to, I'm inclined to believe the death didn't happen because I can't find any mention of it anywhere which even if it happened in the largely preinternet age, I find unlikely. I did find another mention of the accident (which if the description in the other forum is correct was due to user error) here [37]. Nil Einne (talk) 05:11, 8 November 2015 (UTC)

Some of them are chairlift accidents, but it seems that someone, either a rider or an operator, has to do something really stupid to cause the accident.--Denidi (talk) 12:05, 8 November 2015 (UTC)

Which of this definitions is the correct with respect to this axis?

Which of these 9 definitions of axes, that mentioned in Merriam-Webster dictionary, is correct with respect to the axes that draw anatomy plans? 78.111.186.3 (talk) 14:56, 7 November 2015 (UTC)

The longitudinal axis would fall under 1b and 1a. Sagittal axis would be 1a. Some pictures include a 'frontal axis' and that is less clear to me... perhaps number 9 or number 5? 99.235.223.170 (talk) 15:30, 7 November 2015 (UTC)

(ec) That would be 1(d): "one of the reference lines of a coordinate system" - in anatomical drawing, the axes are broadly named (Anatomical_terms_of_location#Axes) Anterior/Posterior, Dorsal/Ventral and Sinester/Dexter...but when the drawing is of a limb that can rotate and therefore be aligned in various ways, separate terminology is applied (Medial/Lateral and Proximal/Distal). SteveBaker (talk) 15:33, 7 November 2015 (UTC)

You are probably correct. FWIW, I'm more used to referring to them all as 'planes', though my anatomy schooling is long behind me. 99.235.223.170 (talk) 19:04, 7 November 2015 (UTC)

The acceptable names for the axes

Do these letters indeed represent these measures as follow?

X – measures the width

Y – measures the length

Z – measure the depth

20:44, 7 November 2015 (UTC) — Preceding unsigned comment added by 78.111.186.167 (talk)

I would swap round X and Y, and use "height" if the Z axis goes upward, but conventions vary. Lower case letters x, y and z are normally used for the measurements, with capital letters being reserved for the axes. Dbfirs 20:58, 7 November 2015 (UTC)

Convensions vary from places to places. Z will be the most likely the less relevant of the 3 dimensions. If you are drawing a map, you might as well forget the heights, so Z will be height. If you are writing a 3D engine for a game however, you might think of X and Y the width and the height to fit the monitor view point and make Z the depth. So It depends.

Also, I just noticed you used the word "length". While it would be the right word if you were describing a pool, I'd rather use "height" most of the time to avoid confusion. Iluvalar (talk) 22:23, 7 November 2015 (UTC)

... that would be the answer on the computer help desk, but the words associated with the axes are just conventional. You can choose whatever seems best for your application, and you can rotate the axes as you wish. Dbfirs 22:40, 7 November 2015 (UTC)

Length, width, height, depth, and breadth are five of the common words we use in English to describe three spatial dimensions. You can also throw in an "ana_(mathematics)" or "kata" if you want to talk about four. So there's not a one-to-one function that maps the words to the dimensions, and no unique "best" choice. If you're dealing with a Hilbert space such as a frequency domain, you need infinitely many dimensions, so we just call them something like ${\hat {f}}_{1}\ldots {\hat {f}}_{n}\ldots$. As Dbfirs says, this is just convention, and there's no one "right" assignment, though the one you give is indeed fine and common, and acceptable :) SemanticMantis (talk) 22:58, 7 November 2015 (UTC)

How to describe 2D

I have two options two describe 2D positions (maybe you have more and better): 1) "Each position can be described as a result of two axes". 2) "Each position can be presented by two different axes." 78.111.186.167 (talk) 23:36, 7 November 2015 (UTC)

Try "Each position can be uniquely described by coordinates along two perpendicular axes". StuRat (talk) 00:42, 8 November 2015 (UTC)

Note that they don't have to be perpendicular, as long as they're not parallel. Tevildo (talk) 02:40, 8 November 2015 (UTC)

I suppose, but it doesn't seem very practical to use such a system. StuRat (talk) 08:03, 9 November 2015 (UTC)

See Nomogram for some examples of non-perpendicular (and, indeed, parallel) axes. Tevildo (talk) 08:37, 9 November 2015 (UTC)

That does not satisfy the condition that each position is uniquely described by coordinates along two axes - each point on the central axis can be represented by an infinte number of pairs of coordinates on the other two axes (corresponding to lines of different angles through the point). MChesterMC (talk) 09:50, 9 November 2015 (UTC)

These questions are confusing. What is it that you don't understand about one, two and three dimensional geometry? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:21, 8 November 2015 (UTC)

Now I understand it well. Thank you. 78.111.186.167 (talk) 06:11, 8 November 2015 (UTC)

I think the axis stuff is confusing. Here's a simple approach: a 1-D object has length only; a 2-D object has area only; a 3-D object has volume. ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:48, 8 November 2015 (UTC)

Silicone sealant for DIY waterproofing.

It is possible to prepare a mixture for waterproofing fabric by mixing together white spirit and the right kind of silicone caulk/sealant. The right kind of silicone sealant is one that does not smell of acetic acid. It cures differently. One such product is GE Silicone II but this is relatively expensive where I live. Could someone tell me whether [this product called Silirub 2] would be suitable? It's chemically neutral although it still requires moisture to cure, according to that specification sheet. — Preceding unsigned comment added by 78.148.104.242 (talk) 23:59, 7 November 2015 (UTC)

A neutral sealant like this does seam better for your application on fabric. As to the best activator in order to get it to cure properly and as to whether this product will obtain the desired results. I would contact the UK distributor here: [38] Then tell them your application, and ask them if their product is suitably and how to apply it etc. I'm wondering is your trying to waterproof something like the hood on top of say a VW Campervan in which case it is better (and cheaper) to buy the finished fabric or maybe a liner for a pond? Intrigued - do please tell. I may been there all ready and got the tee-shirt. --Aspro (talk) 12:14, 9 November 2015 (UTC)

November 8

Any good scientists to convince my dad of evolution?

This is following my earlier post asking for evidence of evolution to convince my dad of it.

I did my best, but my only expertise in science is pretty average grades in GCSE's (high school) so it was difficult to respond to certain objections.

Would somebody knowledgable on the subject, especially fossil records, dating methods, etc be available to correspond with him via email? Time and timing isn't a factor, so you would just respond whenever you have a couple of minutes. Thanks, 2.102.187.59 (talk) 02:48, 8 November 2015 (UTC)

It's probably best to get your answers from the Talk.Origins page (see previous thread - this is the URL); or, of course, we can answer them here. One point I would make - you're unlikely to be successful if the argument turns into an attack on his religious faith. You'll need to show him that acceptance of evolution is compatible with Christianity, not that the two are contradictory. A discussion of the spherical Earth theory can be helpful - does he believe that the Earth is round? If so, he's rejecting a literal interpretation of those parts of the Biblical text that say it's flat (Job 26:10, Revelation 7:1), and that the sky is held up on pillars (Psalm 75:3, 1 Samuel 2:8, Job 9:6): will it challenge his faith to reject a literal interpretation of Genesis 1? If he _is_ a Flat Earther, then giving up is probably the best idea. Tevildo (talk) 03:16, 8 November 2015 (UTC)

Talk.Origins just isn't feasible, given just how specific and unrelated to his objections the entries are. In response to this video - https://www.youtube.com/watch?v=54e5Bz7m3do - he grabbed on to the part where the guy said carbon-14 age is changed through solar and geological activity. I think it would be too much back and forth to post here though. Only direct email would work. He's not a flat Earther, just a guy in his 40s with a relaxed belief in Christianity who thinks humans have been here for a few thousand years and it's ridiculous to think we could've been monkeys. 2.102.187.59 (talk) 03:40, 8 November 2015 (UTC)

Well the real point that should be conveyed is that carbon dating is only one of many, many pieces of evidence for evolution and the age of the Earth. Even if someone discovered tomorrow that all carbon dating was wrong, you would still have to explain all the other evidence of evolution. You might want to look at evidence of common descent, age of the Earth, and RationalWiki's list of evidence against a young creation. And maybe "How come there are still monkeys?". The "humans have been here for a few thousand years" is its own special brand of wrong. I'm getting young Earth creationist vibes, unfortunately. Anyway we have evidence of human existence for tens of thousands of years. Maybe ask where he thinks Göbekli Tepe or the prehistoric technology we find lying around everywhere came from. --71.119.131.184 (talk) 08:18, 8 November 2015 (UTC)

Why do you feel the need to convince him of a scientific theory? How would it improve his life on earth? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:19, 8 November 2015 (UTC)

May as well try, no harm in it. 2.102.187.59 (talk) 03:40, 8 November 2015 (UTC)

If he gets mad at you and never wants to speak to you again, would that feel harmful? ←Baseball Bugs ^{What's up, Doc?} carrots→ 07:45, 8 November 2015 (UTC)

I'll just let Carl Sagan answer this question. --71.119.131.184 (talk) 08:18, 8 November 2015 (UTC)

I'll give it a shot - I've convinced a few people in the past. You can find my email address on my user page (User:SteveBaker). SteveBaker (talk) 05:02, 8 November 2015 (UTC)

I think it is important to distinguish between science and religion here - the goal is not to "defeat" religion, but to acknowledge and respect it. An omnipotent Creator could have written up the universe in any order, on any schedule - like a human author, God could write a basic scene with a few plot elements, then stitch in a backstory. Like any author, God might decide to introduce new concepts, change the settings where events happened, alter the very physics of the world being written about, revising the entire draft, beginning to end, as many times as desired. Sometimes an author might even try writing a character into a tough situation to see how he or she would react to it, gain some insight from that, but scrap that part of the draft later (the problem of evil, you might say).

The key then, here, is to recognize that what we are trying to prove is not that the world is random and humans are a haphazard, unplanned thing whose ethics should be patterned on the notion of relentless, mindless competition to pass on genes. We don't know why reality is what it is, or if it sought what it is supposed to accomplish - we can't even prove that what is is; that's an axiomatic faith, not science. No, what we are trying to prove is a much smaller thing, namely, that the world as we observe it (natural science) follows predictable natural laws that we can use to our advantage, and natural selection is one of them.

It is not wicked to read a lesson that God engraved into the world with such precision - the deep time frame implied from telescopic observations of the distance of dim stars and laboratory measurements of the speed of light, or the procession of fossils and their correspondence to the molecular divergence of the genomes of organisms. To the contrary, there is real good to be accomplished by understanding evolution - understanding the evolution of viruses like HIV within the body, the origin of new species like measles, the use of natural selection principles to select a population of cells that display immunological tolerance, and the subsequent clonal selection response against an invader.

Do humans have to follow natural selection as if it were a moral law? No. Natural laws challenge us, and if they cannot be broken, we don't have to worry about breaking them. Darwinism credits Herbert Spencer for inventing the phrase "survival of the fittest", but this doesn't mean that we should embrace a cruel morality, any more than we should jump off a cliff to respect the primacy of gravity. It is at this point that religion shines, showing us other paths to follow that aren't so downward. Wnt (talk) 12:49, 8 November 2015 (UTC)

• To me the most compelling argument is to focus on the age of the Universe. If we look through telescopes, we can see stars that appear to be hundreds of thousands of light years away, and galaxies that appear to be millions or even billions of light years away. How is that possible, if the Universe is only a few thousand years old? Did God create the light we receive in mid-flight, thereby showing us events that never actually happened? Or is the Universe really millions of times smaller than it appears to be? Neither alternative is easy to defend. In Creationist cosmology this is known as the starlight problem. Looie496 (talk) 17:57, 8 November 2015 (UTC)
  • They could say your measurements are inaccurate. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:24, 8 November 2015 (UTC)
    • That's like saying Columbian druglords did it, Bugs. It's an arbitrary objection based upon no evidence (who has better distance estimates?) raised against a position which does have a whole coherent system of observations behind it. If you actually understand the hard sciences, you get to the point where you have to posit an evil demon (brain in a vat) objection, and claim that God is so malevolent he would even order Abraham to murder his first-born son as a . . . I mean is so malevolent he would create fossils and starlight to deceive us. Personally, with a "God" like that, I'd prefer the more reliable company of Lucifer. μηδείς (talk) 22:37, 8 November 2015 (UTC)
      • The point being that a true believer will have a counter-theory for everything the OP poses. I would still like to know why the OP is so hell-bent on creating trouble with his father. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:44, 8 November 2015 (UTC)
        • Yes, even the uber-combative and ever-vindictive Ayn Rand argues that one should not try beyond polite discussion of your own ideas to convert one's parents. As for scientists, I too would go with Carl Sagan. μηδείς (talk) 00:42, 9 November 2015 (UTC)

I have a keen interest in evolution and I have several close relatives who reject evolution on religious grounds. I have listened to literally hundreds of hours of “evolution” debates and have even participated in a few informal debates myself. Let me tell you something from experience: it is nearly impossible to convince someone who doesn’t believe in evolution for religious reasons that evolution is true using facts about evolution. I heard it explained this way which I think is completely true: For religious people their position is like supporting the right football team, it’s not about which position has better “facts”, it’s almost exclusively about being on the “right side”. For them, their “authorities” tell them that to be a good Christian or Muslim or whatever the religion is, they must reject evolution, that’s it, that’s what you are arguing against. Try to convince someone they support the wrong football team, that’s essentially what you are up against. It’s not completely impossible, but it takes a lot more than “facts”. Don’t forget that Satan is the deceiver, the prince of lies, He can make up extremely convincing arguments that support evolution, but it’s not up to your fallible mind to decide for yourself, you need to trust in God to tell you the real truth. That’s the way these people think, that's what you are up against. As for the religious people in my life, I also have not tried to convince or convert them, I agree with the above, it's not worth it. The most I do is occasionally, when there is a cool science story, not even related to evolution, I try to share and discuss it with them to expose them to how real science works and how wonderful it is. Vespine (talk) 23:02, 8 November 2015 (UTC)

I'll ask my original question because I think it's pertinent. Why do you believe in evolution? If your understanding is so limited that you believe it because someone else told you it was true, that is no different and no more authoritative than a creationist viewpoint. You would be better served to learn the science yourself so you can use it as a foil rather than simply relying on an appeal to authority. Believing Carl Sagan more than a creationist simply because he's Carl Sagan is not a rational argument that will convince anyone. --DHeyward (talk) 03:33, 9 November 2015 (UTC)

I actually think this completely misses the heart of the issue. Everyone believes they have GOOD REASONS to believe ALL of their beliefs, including people who deny evolution. NO ONE who has made their mind up on a subject thinks their understanding is "limited". Ultimately, I can't tell you I completely understand radiometric dating, or DNA analysis, or cladistics and I bet you can't say that either: ultimately you have to submit to the expertise of someone who you trust, it just happens that the people YOU and I trust are scientists who have spent their lives learning about this stuff, and people who deny evolution submit to the 'expertise' of people like Ken Ham and Kent Hovind. Of course you can say "but I "understand" how it works, I "see" the evidence of it in action, etc, well i'm afraid the other side say the same thing. Vespine (talk) 04:09, 9 November 2015 (UTC)

And in case you doubt they say the same thing, Kent Hovind has about 10 hours of lectures 'debunking' evolution freely available on the internet. To someone like you and I it's an exercise in logical fallacies, circular reasoning and pseudoscience, but to someone who is on the other side. That's why websites like talk origins and creation wiki can exist side by side for 10 years. Vespine (talk) 04:36, 9 November 2015 (UTC)

What is the relation between "coronal plane" to the crown?

How crown can represent this direction of the plan? I don't understand it78.111.186.167 (talk) 06:09, 8 November 2015 (UTC)

Crown is the top (as of a head), or the top surface (as of a tooth). A coronal plane lies between the front and the back. A coronal plane is generally perpendicular to the crown of the thing the crown is the crown of, and intersects it from side-to-side. The Transhumanist 09:27, 8 November 2015 (UTC)

Wild horse and horseshoes

How did wild horses survive in the wild without horseshoes? What happens when they experience excessive wear on their hoofs? Or do they not experience excessive wear due to them travelling less or travel on softer ground compared to the domesticated horses? 731Butai (talk) 13:21, 8 November 2015 (UTC)

See Horse hoof and Natural hoof care, suggesting that this isn't really an issue for wild horses. Mikenorton (talk) 14:17, 8 November 2015 (UTC)

It is explained pretty well in Horseshoe#Reasons for use of horseshoes. Traveling more on harder ground is good for a horse's feet, as it toughens them up. It's traveling less, and on softer ground that brought about the need for horseshoes. In answer to your concern about excessive wear, keep in mind that "The average hoof grows 1/4 to 3/8 inch per month. Since the average hoof is 3 to 4 inches in length, the horse grows a new hoof every year." The Transhumanist 18:40, 8 November 2015 (UTC)

I saw a horse living wild in Vieques Puerto Rico which had a hoof that had grown so long that the horse hobbled like a woman on high platform shoes she was not used to. The hooves were several inches longer than normal and curved a bit like an overly long fingernail. Apparently it was not anyone's job to catch the horses and trim their hooves. It appeared to be a mare with a foal. Edison (talk) 22:57, 8 November 2015 (UTC)

• Recently: Neglected Horses Had 3-Foot-Long Hooves,Rescuers Say. μηδείς (talk) 00:37, 9 November 2015 (UTC)

Are distal and proximal in anatomy are used for appendicular system only?

According to what I understand, the distal and proximal terms in anatomy are used for appendicular system only? 14:31, 8 November 2015 (UTC) — Preceding unsigned comment added by 78.111.186.167 (talk)

Those terms are widely used in anatomy: "proximal" means "next to" and "distal" means "not next to". If you enter "proximal" or "distal" into the Wikipedia search box, you will see a long list of possible anatomically related completions. Looie496 (talk) 14:40, 8 November 2015 (UTC)

So you say that the answer is: NOT? and these terms are used also for the axial system? I would like to see an example, because I didn't see.78.111.186.167 (talk) 16:02, 8 November 2015 (UTC)

Er, the wording is a bit confusing, but Looie is saying that the terms are used widely in other areas of anatomy. So, the answer to your question "Are distal and proximal in anatomy are used for appendicular system only?" is no, because these words are used on other systems as well. If you want a concrete example, doing as Looie suggested, I entered "proximal" in to the search box and looked for an entry that did not have anything to do with the appendicular skeleton. The first one I saw was Proximal_convoluted_tubule. These are just English words. We even use related words abstractly for things that aren't anatomical at all, e.g. Proximate and ultimate causation. SemanticMantis (talk) 16:29, 8 November 2015 (UTC)

It looks like the question was poorly worded, and that the question the OP meant to ask was, Are there any bones of the axial skeleton whose names involve the terms "proximal" or "distal"? The answer to that question is that I don't know of any, but I don't know the skeleton all that well. Looie496 (talk)

I meant to ask if these terms are used (in anatomy) except of the area of the appendicular skeleton. (according to what I know it can be used in dermatology or other medical professions but always they refer to the area of the appendicular skeleton rather than the axial skeleton) 18:05, 8 November 2015 (UTC)

The terms are also used in dentistry. Arbalest Mike (talk) 16:24, 8 November 2015 (UTC)

• The very simple answer is no. The tip of the appendix, as an apt example, would be considired distal compared to the proximal end where it joins the intestine. Obviously we're not talking limbs here. μηδείς (talk) 22:26, 8 November 2015 (UTC)

See the figure in Phalanx bone. Proximal and distal are pretty widely used in anatomy - wherever you can describe things as near and far. Wnt (talk) 01:33, 9 November 2015 (UTC)

Granted, though in many cases it makes more sense to use 'medial/lateral' when you're not discussing part of an appendage. 64.235.97.146 (talk) 15:10, 9 November 2015 (UTC)

Can the circadian rhythm adjust to days longer than or shorter than 24 hours?

Since all human beings live on planet earth, they all live on a planet with 24 hours a day, and the circadian rhythm is probably adapted to that. But what happens if a spaceship carries some humans from one planet to another, and on this latter planet, the day is much shorter than earth's, as its rotation is much faster? Will humans be adapted to the new planet? 71.79.234.132 (talk) 15:43, 8 November 2015 (UTC)

Circadian rhythms are also affected by photoperiod, and other Zeitgebers. So even with a 24 hour period, different things happen at different times based on day length, temperature, and other factors. Free-running_sleep gives some references on humans being successfully entrained to a 23.5-hour day and to a 24.65-hour day. See also siesta, polyphasic sleep, and second sleep - even with 24 hour days, many people have broken them up differently. SemanticMantis (talk) 16:21, 8 November 2015 (UTC)

Generally there are a range of durations that people can entrain to. The exact edges of that range aren't precisely defined, because stronger zeitgebers allow a wider range. Studies have shown that people can entrain pretty easily to day lengths of 23.5 and 24.65 hours (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1934931/). (Note that 24.65 hours is the length of a day on Mars.) The maximal range is likely to be substantially wider than that, but hasn't been pinned down experimentally (for humans). Based on animal studies, shortened days will probably cause failure of entrainment more easily than lengthened days. Looie496 (talk) 17:02, 8 November 2015 (UTC)

This article, Non-24-hour sleep–wake disorder, could do with a bit more referencing, but it matches both what I remember having read, and what I know from experience. Most people have an endogenous rhythm slightly longer than a day. On my own I would love a 25-hour day. Way back when I was in college mon-thurs and not working I pretty much followed a 25-hr day or even longer, and ended up staying up all night every few weeks to get back on a semi-regular schedule. Even with the end of daylight savings time, I want to go to bed later than the clock hour, rather than earlier, as one would expect. μηδείς (talk) 00:23, 9 November 2015 (UTC)

Which flower is this  ?

http://i.imgur.com/8N9Bt00.jpg which flower is this ? — Preceding unsigned comment added by 39.42.44.108 (talk) 18:41, 8 November 2015 (UTC)

Bluebell. --TammyMoet (talk) 20:44, 8 November 2015 (UTC)

which specie? — Preceding unsigned comment added by 39.42.44.108 (talk) 21:00, 8 November 2015 (UTC)

It certainly looks like it could be some species of Hyacinthoides but what we call a bluebell here in the states is a bit different. Seeing the leaves and knowing the location would help. μηδείς (talk) 22:22, 8 November 2015 (UTC)

The flowers of the common bluebell and Spanish bluebell are quite similar, except that the Spanish version is bigger and has an erect stem rather like the OPs photo. The common bluebell flowers are on a rather droopy stem. The Spanish bluebell is widely grown in British gardens and in some places is threatening to displace or interbreed with our native common ones. See Spanish bluebells threaten future of UK's favourite plant (May 2015) and How can I tell whether bluebells are native ones or Spanish ones?. Alansplodge (talk) 23:03, 8 November 2015 (UTC)

The OP geolocates to Lahore, so if it's a garden plant in that area, Spanish bluebell would seem to be a good bet. Alansplodge (talk) 23:06, 8 November 2015 (UTC)

Normal force in car

Say a car is travelling at a constant velocity, and a person (or, if we want to make things simpler, a block) sits on the passenger seat, with its back and bottom touching the seat. Normally when we sit in a car at constant velocity, we would think that we are in contact with the back of the seat. Yet, if the car and thus the person/block is in constant velocity, then the sum of the forces is zero, so is the normal force exerted by the seat on the person also equal to zero? I ask because, if it was nonzero, what other force could be acting on him? Thank you! 70.54.112.243 (talk) 20:32, 8 November 2015 (UTC)

The seat back angles backward even in its most upright position, so gravity pulls your upper body toward it (obliquely). If the seat back were vertical or tilted forward then you would not press against it unless the car was accelerating or some nongravitational force was pushing you backward. -- BenRG (talk) 21:01, 8 November 2015 (UTC)

With a vertical seat back, you could press against the seat back either by exerting yourself or by scooting your butt forward and slouching in the seat. In both cases the force opposing the normal force of the seat back on the passenger is the friction force of the seat on the passenger's bottom, without which the passenger would slide forward. -- ToE 22:09, 8 November 2015 (UTC)

Put it this way, if the acceleration of the car was truly zero (in a real moving car this would very rarely be the case), then the forces acting on someone sitting in a moving car would be the same as those acting on someone sitting in a stationary car. Vespine (talk) 22:44, 8 November 2015 (UTC)

You could have a seat back which is at a 90 degree angle to the center line of the car and have the car at a constant speed, but the OP did not specify that the car was n a level surface, so climbing a hill could also force the passenger or load against the seatback. As Vespine said, this would be the same as if the car were stationary on the hill. Edison (talk) 22:52, 8 November 2015 (UTC)

• Let's back up. Touching, and being pressed against are two different things. It requires no force for a block touching the back of the seat behind it to remain touching the seat. Second, if there is no net acceleration, there is no relevant source other than gravity--although this still does not have anything to do with a rigid block on a seat touching or not touching the back of the seat. Third, the human body is held only held rigidly upright against gravity by the force exerted by muscles that keep the spine erect. If one relaxes them, one will normally slump back against the seat due to the curvature of the spine; that curvature converts compression of the spine by gravity into a slumping forward of the head and a pushing backwards of the lower back. Fourth? Well, I am not sure there is really a relevant fourth. μηδείς (talk) 00:34, 9 November 2015 (UTC)

In a non-accelerating car, the only force acting on occupants is gravity. --DHeyward (talk) 03:21, 9 November 2015 (UTC)

Meaning that the occupants will accelerate downward at 1 g? -- ToE 06:48, 9 November 2015 (UTC)

No, it means they will only feel the force of gravity. --DHeyward (talk) 08:57, 9 November 2015 (UTC)

It sounds as if the questioner is considering the free body diagram of a nonaccelerating passenger, and rightly expects the vector sum of forces to be zero. The force of gravity on the passenger is countered by the normal force that the seat applies to their bottom, (though just how that force feels will depending on how comfortable the seat is). -- ToE 14:40, 9 November 2015 (UTC)

Radiation resistance

If I send a high frenqency sine wave down a piece of 50 ohm coax that is open at the far end, will there be any detectable em radiation in the space beyond the end of the coax? If not, why not?31.55.80.65 (talk) 21:53, 8 November 2015 (UTC)

See impedance matching and VSWR. _Theoretically_, a perfect open circuit (infinite impedance) will reflect all the RF energy back down the cable (and into the transmitter, which may not like it) - the reflection coefficient will be 1.00 and the VSWR will be infinite. However, a real cable with the end cut off will not have infinite impedance, and will therefore radiate some detectable energy. The actual amount of energy radiated will depend on the impedance match between the cable end and free space, which will be very dependent on the frequency of the RF and the precise geometry of the cut end. Tevildo (talk) 22:22, 8 November 2015 (UTC)

The match is well defined: its 50R looking into 377R. So do we actually detect that amount of power transferred or is it affected by some other factor such as near field effects?31.55.77.23 (talk) 00:11, 9 November 2015 (UTC)

377Ω is the impedance of free space - that doesn't mean it's exactly the impedance that is encountered at the end of an unterminated wire, but it's a pretty decent rule of thumb. If we use free space for the impedance at the end of the unterminated wire, you can use the simplified reflection coefficient equation:

$\Gamma ={Z_{L}-Z_{S} \over Z_{L}+Z_{S}}$

...and note that transmitted power is given by $1-\Gamma ^{2}$. That equation estimates about 40% of the power will radiate away - which is sort of what we expect, because an unterminated 50 ohm trace is a lot like a crummy dipole antenna!

...but because you said you're modeling unterminated coaxial cable - it's more probable that the unterminated impedance is not well-modeled by 377Ω, because of the unique geometry of coaxial cable. Some sources say ∞ is a better model for the unterminated impedance of coaxial cable - if I really cared about the value, I'd use a TDR or a VNA to actually measure my cable in my lab, because this kind of real-world RF stuff defies theoretical calculation!

This is covered in our articles on transmission coefficient, reflection coefficient, and so on. These are simplified equations, and they assume a specific simplified model of the unterminated wire; and it also assumes that 377Ω is a good model for the impedance of the air at the frequency you're using. Nimur (talk) 02:36, 9 November 2015 (UTC)

November 9

Asymmetrical airplane seating.

Several smaller airplane types have asymmetrical seating arrangements such as AB_CDE or A_BC (where "_" represents the aisle). Although the asymmetry is near the plane's centre line it must cause some imbalance. Is this compensated for by ballast or the arrangement of other components, or by aerodynamic trim settings, or by the pilot's control, or is it negligible ? 99.224.93.200 (talk) 02:04, 9 November 2015 (UTC)

Yes, it's compensated for. A commercial aircraft's crew (including the ground crew that loads cargo) has to take into account the load distribution of the craft. The pilots have to compute the laden weight of the craft before takeoff, because they need it to calculate things like the V speeds, as well as how much fuel to carry. If necessary they'll sometimes ask passengers to move around to even out the weight distribution; this is more common on aircraft that are smaller or have many empty seats. --71.119.131.184 (talk) 02:42, 9 November 2015 (UTC)

I think that's only the fore/aft loading and center of gravity. Port/starboard loading is rarely considered. Note that many aircraft can have unbalanced fuel loads in each wing which have a much larger moment than any centerline aisle gap. --DHeyward (talk) 03:18, 9 November 2015 (UTC)

Hmm, I'm not disputing what you're saying, but I know some planes have fuel lines that can transfer fuel between the tanks. Is that more for ensuring one side doesn't run out of fuel? --71.119.131.184 (talk) 03:39, 9 November 2015 (UTC)

The fuel can get out balance and gravity is the biggest culprit, but left/right imbalances don't normally disturb stability. One of the differences in a commercial jet and and private small planes is the relative differences between the center of lift and center of gravity. In commercial jets, the aircraft is loaded mor ecarefully with less stability to improve fuel efficiency. It's all about keeping the center of gravity and center of lift in their proper places. Fuel transfer that's done for efficiency would be to move fuel from a forward position to an aft position. Left/right imbalances just aren't as important for stability. Airplanes turn by creating left/right lift differences which rarely cause a problem. But pitch up problems create stalls and an unrecoverable pitch down will just crash. A plane can do a 30 degree banking turn without losing altitude until it runs out of fuel but a 30 degree pitch up climb will eventually stall. --DHeyward (talk) 08:52, 9 November 2015 (UTC)

Cancer in inverterbrates

Here is one of the strangest news stories I have read in a long time. http://www.foxnews.com/health/2015/11/05/man-dies-after-tapeworm-inside-him-gets-cancer.html?intcmp=ob_article_footer_text&intcmp=obnetwork

As Veterinary oncology says, there has been a lot of research into cancer in cats and dogs, and presumably also into farm animals. But what “lower” animals that are still multi-cellular and therefore metazoa (that is, higher animals) get cancer? We know that elephants seldom get cancer because they have multiple copies of an anti-tumor gene that is present in all mammals. Elephants have been long-lived longer than humans have. We now know (whether we knew it before) that flatworms can get cancer. We now know that, in rare cases, it can actually kill a human.

The whole article on cancer seems to be about cancer in humans, and it should be mostly about cancer in humans. I had known that there had been research into cancer in sharks, and that there is argument over whether sharks get cancer.

We now know, whether we did or did not, that worms can get cancer. This does imply that cancer appears very close to the base of the evolutionary tree. (Don’t get your backbone removed. It won’t help.) What is known about cancer in inverterbrates? Maybe we need an article, or a section of an article. We now know that flatworms can get cancer, and so anything above them on the tree presumably can.

Comments?

Robert McClenon (talk) 03:29, 9 November 2015 (UTC)

This isn't really the place to just have a discussion. Do you have a specific question other than, what do people think? I've found a few research articles just by googling inverterbrate cancer. I also remember reading that there is good evidence dinosaurs had cancer, (for those people who claim it's a "modern disease". Vespine (talk) 03:55, 9 November 2015 (UTC)

I don't see any reason why all multi-cellular animals and plants wouldn't be subject to cancer. Indeed, if we find any which appears to be 100% immune, we might do well to study it. StuRat (talk) 05:57, 9 November 2015 (UTC)

My question was prompted by the fact that Wikipedia doesn't answer what I thought was a reasonable question, whether invertebrates and plants get cancer. In this one very strange case, a human died of flatworm cancer. (He might have died from the flatworm anyway.) I asked the question because Wikipedia doesn't answer it. Robert McClenon (talk) 08:24, 9 November 2015 (UTC)

Devil facial tumour disease is an interesting animal cancer. StuRat (talk) 08:41, 9 November 2015 (UTC)

Hence Category:Types of animal cancers.--Shantavira|^{feed me} 08:53, 9 November 2015 (UTC)

There is a species which is apparently immune, and there are studies into it - see Naked mole-rat#resistance to cancer. Now, the fact that this is a surprising discovery would suggest than cancer is prevalent in most other well-studied species. MChesterMC (talk) 09:30, 9 November 2015 (UTC)

• Before anyone says otherwise, sharks do get cancer. When plants get cancer, that's usually called a gall (although not all galls are equivalent to animal cancer) – see crown gall for an example. Smurrayinchester 09:39, 9 November 2015 (UTC)

Cancer has been well studied in Drosophila, and there are many proto-oncogenes involved that are homologous to those in humans. [39] Therefore, cancer traces back to the Urbilaterian, at least. However, I didn't quickly find information about whether Cnidaria are subject to it... I really ought to look harder. Wnt (talk) 13:32, 9 November 2015 (UTC)

Survival: Humans Unable to Eat Leaves for Nutrition. The Whys and Hows. ?

So many herbivores eat leaves, but it has always been said that humans can't eat leaves (with a few exceptions), supposedly because they are so full of cellulose and so fibrous, and evolution has seen us become lacking of the necessary enzymes to break cellulose down. Maybe this is so, but when I learn or read about people in survival-situations, lacking food, it seems so... unnecessary to starve when there's trees and leaves everywhere, because there is nutrition in them, albeit not that much.

I mean, wouldn't it be better to eat at least a little bit leaves than nothing?? Leaves are not that nutritious, I know, which is why many herbivores spend big chunks out of a day simply eating, but so long as we ate only a little bit and not too much at the time, shouldn't our bodies be able to cope with it better than having no calories at all? What if one boiled the leaves first, would it make any difference at all?

I've been told that Pine-needles is one of the exceptions, that this is in fact useful as "survival-food". Is this true? Pine-trees are widespread in abundance. It would have made things easier, but surely it ain't that easy, no?

2A02:FE0:C711:5C41:5D0C:5C73:C6D4:4C90 (talk) 10:19, 9 November 2015 (UTC)

Few animals can actually digest cellulose themselves. Most animals that eat cellulosic material rely on microbes in their gut to do the actual digesting. Their bodies then absorb the breakdown products. So, "become lacking of the necessary enzymes" is not the case; our ancestors never had the enzymes to begin with. The evolution of herbivory is a good object lesson in evolution. The key thing to remember is that developing and maintaining a trait incurs a cost to the organism. Traits only become widespread in the presence of favorable selective pressure. Herbivory is an expensive trait, as it promotes heavy specialization; a digestive tract optimized for digesting cellulosic material is not very good at digesting anything else. So, species generally won't develop herbivory unless their available food sources are constrained. The other key point about evolution is that it's not intelligently directed. Evolution is the "blind watchmaker", as Richard Dawkins put it. Evolution can only act on existing organisms, groping blindly for solutions that promote fitness. So we get ridiculous jury-rigged solutions like pandas, who try to digest bamboo with a carnivore's digestive tract, or herbivores who have to eat their own feces in order to digest anything. Even if there are situations where an organism might benefit from herbivory, natural selection can't just pull the trait out of thin air. One other thing of note: you should remember that plants don't want to be eaten (except, in the case of flowering plants, their fruits, and even then only by the right species and at the right time). Many plants deploy defenses against things trying to eat them, which is something else herbivores have to adapt to. --71.119.131.184 (talk) 11:03, 9 November 2015 (UTC)

There are plenty of leaves humans can and do eat. Here is a very long list of leaves humans regularly eat (I had some Senegalia pennata with dinner tonight myself).--William Thweatt ^TalkContribs 11:14, 9 November 2015 (UTC)

We don't get much energy from eating leaves. If we kept eating leaves we wouldn't have become intelligent beings. We relied on other animals to digest leaves. We killed that animals and cooked their meat and got much more energy efficiently. We spent less energy and got more energy. So we have lot of excess energy in body. We spent that excess energy in building intelligence. - Supdiop (T🔹C) 11:45, 9 November 2015 (UTC)

The extraordinary kinetic stability of cellulose never ceases to amaze me. We know the potential energy is in there - just toss a log on the fire! But as described at [40], cellulose is chemically almost the same thing as starch, which is so easy to degrade that you have an enzyme in your saliva that starts making it taste sweet the moment it touches your tongue. Yet - somehow, that I don't really understand - it manages to crystallize into such a configuration of hydrogen bonds that water cannot penetrate it, and for some reason that I also don't understand, enzymes can't readily cut it except at the ends. And when I say "enzyme", I mean "billions of years of evolution have failed to crack this, other than with some substandard solutions for cellulase that use such brute force that they release methane trying to get sugar subunits apart (think about that!) and more to the point require large fermentation spaces and times to get the cellulose digested. Now that is tough enough, but plants are savvy to the whole notion of getting eaten and add lignins to lock it up even tighter. Lignin is somewhat similar to melanin or humic acid, or even the synthetic polymer Bakelite, which links phenols together. Wnt (talk) 13:22, 9 November 2015 (UTC)

It's a question of "quantity rather than quality" here. For humans to digest any carbohydrate, it first needs to be in the form of a monosaccharide. In order to get it there, polysaccharides need to be broken down into monosaccharides, a process that (as you note) can really only be done from the ends of the polysaccharide chain. The difference between starch and cellulose is, as you not, merely one of the length of the chain; starch is "chains short enough for humans to be able to digest reasonably completely", with cellulose being "chains too long for humans to break down before it leaves the part of their digestive system where this can happen". For example, this chart I got out of a recent scholarly article, it discusses chain length of two common starches, potato and maize, and shows that the mean chain length (number of saccharide monomer units) to be roughly 20-21 units long. As you can see here, the average chain length of cellulose polymers is somewhere over 10,000 units. Given that you can only digest these from the ends, that means that starches should (with all other things being equal) break down in the gut roughly 10,000/20 = 500 times faster than cellulose. So, given that [transit time in the digestive system varies from 24-72], if it takes 24 hours to digest and pass starches from eating to exceretion, it would take a year and a half to digest the same mass of cellulose. As in, it's not going to happen. --Jayron32 13:34, 9 November 2015 (UTC)