Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

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

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

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

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

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

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

August 20

Hypothermic/hypothermia surgery

I have found Google information about the use of deliberate hypothermia in brain and cardiac surgery. It is apparently being used in Ecuador for, for example, foot surgery, but I can't find any references to this technique. Anybody out there have better sources and or knowledge? Thanks Bielle (talk) 02:57, 20 August 2013 (UTC)

Cryotherapy would be a good place to start. 24.23.196.85 (talk) 04:20, 20 August 2013 (UTC)

Thank you, but cryosurgery is used only for very small parts of the body. The description I was given was of some sort of "ice machine" which "froze" the whole lower half of the body. This cannot be literally true, because of the response of cells to freezing. Any other suggestions? Bielle (talk) 16:15, 20 August 2013 (UTC)

Wikipedia Has An Article On Everything! - see Therapeutic hypothermia. Alansplodge (talk) 17:49, 20 August 2013 (UTC)

sun setting at different times

A couple of weeks ago while I was driving home (Central Ontario, Canada), I pulled over to take a picture of an amazing sunset. Later, I sent the pic to my friend in Ghana and noted that the pic was taken at about 8:30 pm. She was surprised as the sun set in Ghana at about 4:30 pm. When I look at a map I see that Ghana is much closer to the equator than Canada is. Does this explain why the sun set at different times in the two countries? 173.35.158.194 (talk) 03:25, 20 August 2013 (UTC)

The short answer is "yes". See Sunset for a better one. Bielle (talk) 03:33, 20 August 2013 (UTC)

Are you sure that she said sunset was at 4:30 p.m. in Ghana? Does she live behind a big hill? Ghana is not on a time zone significantly ahead of its local time. Dbfirs 11:24, 20 August 2013 (UTC)

Sunrise and sunset in Ghana is never far away from six o'clock, it is quite close to the equator and in an appropriate timezone. I was wondering if they were referring to what the time was in Ghana when there was a sunset in Ottawa, it is four hours out currently but unfortunately the wrong way for this so I haven't the foggiest what's happening. Dmcq (talk) 11:40, 20 August 2013 (UTC)

Time zones and daylight savings time could also shift sunset times by up to 2 hours in Ghana relative to Canada. There could also be differences in how "sunset" is defined. It could be when the first part of the Sun goes below the horizon, or the last bit, or when the sky goes black. StuRat (talk) 14:33, 20 August 2013 (UTC)

There is no way the sun sets in Ghana at 4:30 PM. Dauto (talk) 14:53, 20 August 2013 (UTC)

Day length explains how surise and sunset vary by latitude and where the earth is in its annual orbit around the sun. Ecliptic explains the cause behind it. Hope this helps.Diwakark86 (talk) 18:50, 20 August 2013 (UTC)

Ghana runs on GMT all year, and no region is very far from the meridian (between four degrees west and two degrees east), so if the friend in Ghana really did mean 4:30 local time then the only explanation is that she lives just east of a hill, and perhaps just east of a tall forest. Local terrain can significantly affect the time at which the sun apparently sets, though daylight will remain for much longer. Dbfirs 20:31, 20 August 2013 (UTC)

Tomorrow, the sun will set at 6:12 pm local time [1] in Accra, Ghana. That's not 8:30 pm, but it's a far cry from 4:30. --74.43.43.6 (talk) 03:03, 21 August 2013 (UTC)

Thanks everyone. I suspect that it is a combination of definition and language. 173.35.158.194 (talk) 02:27, 22 August 2013 (UTC)

There are various websites that allow computation of times of sunrise and sunset, simply by nominating latitude, longitude and timezone. I have successfully used the following site to compute a table of sunrise and sunset in Ghana for the whole of 2013: Sunrise, Sunset and Twilight Times. Dolphin (t) 23:29, 22 August 2013 (UTC)

Anchors unzipping

I've recently watched The Eiger Sanction with a friend of the family, and he told me that he found the final scene implausible: he said that when anchors unzip from the top because of excessive strain, they all go, so it would be impossible for Clint to remain hanging from his rope while the other three fall to their death. However, I have my doubts about this -- if the bottommost anchor was driven in much more firmly than the others, I don't see why it can't remain in place. Neither of us is a professional mountaineer, so I'd like some educated commentary on the subject. Thanks in advance! 24.23.196.85 (talk) 04:34, 20 August 2013 (UTC)

The Eiger article has an unsourced comment saying that the film crew included experienced climbers to ensure the accuracy of the climbing scene. The novel was written before the invention of spring loaded camming device so I'm not sure, but I would say that with modern equipment having 3 anchors fail and the fourth hold would be possible - after all, even if they fail the other anchors should slow down the fall - but I don't recall even seeing such a thing happen (I've seen one or two anchor failures happen though, with modern equipment trad climbing). Not having seen the movie, I have a hard time imagining how that situation would let one member survive but not the others; also note that even if the fourth anchor holds, the distance fallen essentially doubles with every missed anchor, and if there is any angular momentum the climber would likely kill themselves by crashing into the cliff. Effovex (talk) 15:12, 20 August 2013 (UTC)

A well placed cam can stop a fall of well over 10 kN. I would guess a well placed pitons would be able to hold at least as much and probably more, as the problem with pitons isn't their strength but the damage they cause to the surface (see Clean climbing). If you can provide a description of the distance between the pitons and the weight of the climbers, I'm sure someone could calculate the maximum amount of force that would be exercised on the remaining anchor. Are they climbing strictly vertically? Effovex (talk) 15:23, 20 August 2013 (UTC)

This climbing forum gives a generally favourable review to the film; there are a few quibbles but nobody mentions the failing pegs. John Cleare is mentioned as an advisor. Our Eiger article also states (with a reference) that Dougal Haston, and Hamish MacInnes were involved. Alansplodge (talk) 17:42, 20 August 2013 (UTC)

Thanks! So I guess this situation would be possible but unlikely? 24.23.196.85 (talk) 06:29, 23 August 2013 (UTC)

Human body maximum performance

I read an article which claimed that the human body overall performs at its best between ages 25 and 28. Is this true? Does it differ between people, gender race etc? Clover345 (talk) 10:21, 20 August 2013 (UTC)

What kind of performance are you talking about? 163.202.48.126 (talk) 11:26, 20 August 2013 (UTC)

Aging and athletic performance. The physical peak for "most sports" is 25 to 35. This is likely to be lower for women - I doubt you'll find anything concrete for the different races. Some sports however do require more training than others and you might find that older players tend to do better than younger ones (e.g. golf). Also [2]. If you're talking about academic performance or something else then the answer will be different. 163.202.48.125 (talk) 12:11, 21 August 2013 (UTC)

examples of organs which made of some kinds of tissues

Could you give me some examples for organs which made of some kinds of tissues And some examples for tissue which made of some kinds of cells? Thank you a lot!176.13.161.70 (talk) 16:55, 20 August 2013 (UTC)

You may wish to read our articles on organ (anatomy), tissue (biology), and cell (biology) to help you do your homework. DMacks (talk) 17:01, 20 August 2013 (UTC)

By the very definition of tissue, all organs are "made of some kinds of tissues". So just pick an organ, and find out how it is constituted. Plasmic Physics (talk) 00:17, 21 August 2013 (UTC)

doing a blood test for who did mastectomy

Today I was in the clinic for blood tests, and I saw that the nurses said to a woman who made mastectomy in one side, that she is allowed to make a blood test only in the another side, because she don't has limph nodes in the side of mastectomy. I also was in the room when it happened but I ashamed to ask about... even it's intresting me. So, here I feel good to ask about:) My questions are: 1. What is the problem or danger to make a blood test in the side of the mastectomy (this is the side where there is not limph nodes). 2. What have to do when a woman made mastectomy in her two sides breasts, can she not be taken a blood test at all, or is there any solution for her? (p.s. It's not medical advice, because I'm a man and just intersting to know the issue. So, please don't note about). thank you. 95.35.232.184 (talk) 17:46, 20 August 2013 (UTC)

Wikipedia:Reference desk/Archives/Science/2013 August 12#Lymph node removal and blood pressure measurement got no responses, but that question does include an answer to the question #1 here. DMacks (talk) 17:56, 20 August 2013 (UTC)

Googling finds lots of hospital (or similar) patient-advice webpages talking about it. They mention a problem with the cuff causing lymphedema (consistent with my previous link). And note pros and cons of the obvious alternative of measuring blood pressure "somewhere else" or "by means other than compression cuff". DMacks (talk) 18:07, 20 August 2013 (UTC)

It is a matter of balancing risk. For a woman with a recent mastectomy, the risk of penetrating the skin on the arm on the mastectomy side, as is required to get a blood sample, is that infections will be more complicated, as part of the role of lymph nodes is to prevent the spread of infection. Infection toxins may build up in the arm due to the poor lymph drainage. For the same reason, women with mastectomies involving the removal of lymph nodes are advised to give up gardening or any activity that has a risk of scratches (or at least wear arm length gloves). After a few years the lymph channels adapt and new lymph nodes grow, reducing the risk. For a woman who has had a mastectomy and lymph nodes removed on both sides, normally the mastectomies will be some years apart. Use the oldest surgery side for blood pressure taking, blood taking, and injections, as this lowers the risk. Note that for mastectomies, whether no lymph nodes are removed, some lymph nodes are removed, or all lymph nodes are removed, depends on the facts of the case, and the judgement and experience of the surgeon. If the cancer is discovered by feel or mammogram and is considered early, only the sentinel lymph nodes in the chest might be removed, and there is no more risk to the arm than for any other woman. Many women who have had breast cancer will have had chemotherapy via a drip in the other side arm. In some cases this will have "burnt out" the surface veins in that arm, making getting a blood sample difficult. The woman should insist that an experienced phlebotomist does it, and not just some ordinary general duties nurse. However, if only a general nurse is available, it's only a matter of risk, nothing to get too uptight about. A blood sample for lab testing can be taken from any surface vein on a limb. If the woman has no lymph nodes in both armpits from a double mastectomy (which is very unusual) blood can be taken from a leg or foot vein. However, as gravity will markedly increase the risk of uncontrolled bleeding, this should only be done in a hospital (or other situation where medical staff can get it under control) under the supervison of a doctor, and the woman will have to remain there until it is certain she won't bleed. — Preceding unsigned comment added by 1.122.245.38 (talk) 00:20, 21 August 2013 (UTC)

Raid Fly Spray

I seem to have an infestation of some kind with Blue bottles and got home from work today with my dining room full of them. So I grabbed a can of Raid fly killer (it may be this product but in the UK it's a blue can marketed as a fly and wasp killer) and sprayed at them directly wherever they were, including walls and windows, shut the doors and returned 15 mins later.

Then I read the directions on the can and part of the warnings state 'keep spray at least 1 metre from all surfaces and walls'. I certainly sprayed a good few surfaces as that's where the flies were sitting. I'm just wondering why, as it's an aerosol, it specifically states not to spray a wall even though spraying it the air leaves the insecticide on all sorts of surfaces.

Is it simply in case the spray rebounds off the surface you're aiming at? I'd think it's still better to aim at the problem rather than spray an antire room in the air and have the spray land on every surface

Thanks in advance --46.208.198.216 (talk) 21:59, 20 August 2013 (UTC)

If you have large numbers of them in your dining room, you'd better find the source... otherwise you can play with that can all you want and get nowhere. It's hard to comment on any potential toxicity without seeing ingredients for sure (not just 'something like it'), and even then it would be disallowed here as medical advice, but my pure guess is that if you can spray it in a room safely at >1m they must be more worried about the solvent than the chemical, i.e. for purposes of dissolving plastic, discoloring surfaces etc. Wnt (talk) 22:05, 20 August 2013 (UTC)

That makes sense thanks, I assumed it was potential toxins left in the home. I appreciate your advice that I should find the source, but this has happened a few times over maybe the past 8 years, this is the second time with flies and also I had a problem one year with bees (I work away from home and got back one weekend with dozens of tiny bees dead in front of the window). I've had pest control companies out and they were at a loss unfortunately --46.208.198.216 (talk) 22:28, 20 August 2013 (UTC)

August 21

Carbon Footprint Q: Whose foot is that, then?

In Sydney, Dick Smith, environmentalist, businessman and aviator, recently hosted a very interesting TV doco on renewable energy. In it, he noted that Australia has one of the largest carbon footprints(per capita)in the world, mainly in consequence of the massive amounts of coal we mine and export.

But that made me think: which party incurs the responsibility for the carbon release: the exporter, or the importer, which in our case is China. If it is the exporter – us – then China is virtually blameless for any carbon debt, as all the nations that sell them coal, iron and the rest are the ones who are fitted up as the guilty parties. But I have read that they too have a very big carbon footprint. Is there some rather shonky bookkeeping going on here, where carbon emissions are being counted twice? Myles325a (talk) 06:22, 21 August 2013 (UTC)

Environmentalists generally prefer alarmism so they would prefer doing the calcs to make the numbers appear worse for everyone. That being said, you could also argue - since the Chinese use the coal they buy from Australia to generate power to manufacture goods which they export to other countries - that those countries should bear the carbon footprint. So the US, which consumes much of the stuff manufactured in China, should have the CO2 from the coal mined in Oz in their footprint. Otherwise see Carbon footprint. In reality the system is quite perverse with everyone pointing to other people's CO2 emmissions to justify themselves not doing enough to cut down their own emmissions. 163.202.48.125 (talk) 08:40, 21 August 2013 (UTC)

That's a bit glib. Acquiring resources, using resources, and obtaining the results are all different activities. You could count the mining operations footprint against Australia, the production using those resources against China, and the shipping of their output against the US.Phoenixia1177 (talk) 10:39, 21 August 2013 (UTC)

The question makes it clear that’s not the case, though. The carbon released from the coal mined in Australia is contributing to Australia’s carbon footprint. Or at least that’s how I interpret the question. 163.202.48.125 (talk) 11:37, 21 August 2013 (UTC)

No, the question expresses confusion about how the accounting is done, and some guesses that things might not be accounted for in the way that we might expect. There are indeed many ways such things can be calculated, but it is wrong to assume that emissions made in CN by burning coal mined in AU are counted as AU emission, merely because the OP is unsure of what's going on. SemanticMantis (talk) 15:27, 21 August 2013 (UTC)

Myles, can you give us a link to any specific reports? We can't really say how the carbon accounting was done unless we can see the original documents (And I can't find/watch the show right now). I will say that coal mining is a major source of emissions, even not counting any emissions from the burning of coal. Consider: all the gasoline to power trucks, electricity for lights, not to mention heavy digging equipment, manufacture of specific tools, etc. All that goes into the life cycle analysis of mining coal, and much of that energy is derived from fossil fuels. So it could be that Smith was basically correct that mining coal is a big part of AU's carbon footprint, even if the burning of said coal in CN is not. SemanticMantis (talk) 15:27, 21 August 2013 (UTC)

Many parties are involved. See "Environmental impact of the coal industry" and "Environmental impact of shipping" and, more generally, Category:Environmental impact by source. Sellers are enticed by high profits, and buyers are enticed by low prices, and often the natural environment (our natural life support system) pays a price. See "Environmental full cost accounting" and "Ecological debt". The natural environment can be affected negatively by resource extraction and processing; commodity distribution, use, and misuse; and waste disposal. A responsible person can do a limited amount of good without community support, but we can all do much more if everyone takes individual responsibility.

—Wavelength (talk) 16:33, 21 August 2013 (UTC)

The point here is "does it matter?" - this is a global problem. If Australia didn't mine the coal, China couldn't burn it. If China didn't burn coal, Australia wouldn't mine it. Who cares which of the two countries is responsible? Either one of them could choose to end it - so in any useful sense, they are both equally at fault. The naive statistic of "National Carbon Footprint" glosses over so many details in a dynamic, interconnected world as to be almost useless. Any simplistic view of the situation has to be viewed as a very general indication of a problem - and the specifics have to be examined before deciding on some course of action. If the world decided that this trade between Australia and China was unacceptable, political pressure would likely be exerted at both ends of the supply chain.

If China was pressured into not buying the coal - probably the Australian mining industry would sell it somewhere else. The sudden glut of coal would result in a dramatically falling price of the stuff on the open market - which would likely result in more Australian power generators burning it instead - and other countries would probably step in to buy Australian coal at this lower price point.

If Australia was pressured into not mining the stuff - the Chinese would buy it from some other country - a shortage of coal on the open market would push up the prices and encourage other countries to step up their production rate accordingly.

No single "fix" for this problem will work. It requires a global perspective. You need ALL coal mines around the world to reduce production and ALL coal fired power plants in every country to reduce their consumption. That kind of global cooperation has proven elusive...which is a very depressing situation.

SteveBaker (talk) 14:10, 22 August 2013 (UTC)

OP myles325a back live. It matters to me Steve coz while I am an environmentalist I despise the Green’s natural position that they can lie thru their teeth whenever they feel the end is worth it, while becoming holier than thou whenever they spot a fib that doesn’t suit their purposes. Activist literature is full of colossal exaggerations and outright falsehoods, and in the end it does their causes much harm, as the public founds out eventually and becomes cynical.

I don’t like propaganda, and I don’t like crappy statistics. I like to know the truth, and if some fanatic is counting carbon footprints twice, then I wanna know about it, and I want the lie exposed. Call me an old fuddy duddy but I’ve had an absolute gut full of the mealy mouthed post modernist view that “there is no such thing as truth”, and it’s all just a matter of what suits you, sir. Myles325a (talk) 05:27, 23 August 2013 (UTC)

Transmission of light through transparent medium

Okay, so in a transparent medium with a refractive index greater than 1, light is propogated with a velocity that is less than c. I understand the wave explanation of this in terms of electromagnetic radiation, distinction between group velcoity and phase velocity etc. But what actually happens at the level of individual photons ? Does each individual photon travel at a speed less than c ? Or do individual photons travel at c but the slowing down is a bulk effect because photons are absorbed and re-emitted by electrons ? Or is the slowing down the result of some complicated interaction involving virtual photons ? I've read the articles on refractive index, speed of light, slow light and transparency and translucency, but they don't seem to answer this question. Gandalf61 (talk) 08:54, 21 August 2013 (UTC)

The Photon article under Photons in Matter goes into it. It mentions scattering and interaction with quasi particles.Phoenixia1177 (talk) 10:53, 21 August 2013 (UTC)

Thank you. Yes, photon says the slowing down is due to "blending of the photon with quantum excitation of the matter (quasi-particles such as phonons and excitons) to form a polariton; this polariton has a nonzero effective mass". So in short, it's quantum weirdness. Gandalf61 (talk) 13:31, 21 August 2013 (UTC)

Or just consider that the photon is itself an excited state of the electromagnetic field, the field in the medium is, of course, described by the free field plus the interactions with the medium and quantizing that will lead to a different beast than quantizing the free electromagnetic field. You can then intepret what you get in terms of free photons that mix with quasi-particles, but then given any Hamiltonian, you can always write that as a sum of two different Hamiltonians, so these intuive pictures are not always unambiguous. Count Iblis (talk) 14:22, 21 August 2013 (UTC)

The wave picture is just as correct as the particle picture. They are different ways of calculating the same thing, mathematically. The particle picture works classically too—loop-free Feynman diagrams give you classical electromagnetism, and the diagrams with loops are quantum "corrections". The phenomenon you're describing is classical, and the quantum explanation isn't fundamentally any different however it's phrased. -- BenRG (talk) 16:06, 21 August 2013 (UTC)

Yes, I understand that the wave model and the particle model are equivalent in the classical limit, when there are a large number of photons. However, the intensity of the incoming light can, in principle, be reduced until only a single photon at a time is transmitted. So the particle model must explain the behaviour of individual photons in a way that replicates the wave model in the limit of large numbers of photons. And any description of the behaviour of individual photons must be a quantum physics model, not a classical model. So I was looking for a description of the mechanism by which an individual photon is refracted and slowed down (or, indeed, speeded up if refractive index is less than 1) as it passes through a transparent medium. Gandalf61 (talk) 09:00, 22 August 2013 (UTC)

What you have to understand is that a photon in vacuum and a photon in a medium are not the same object. In a medium, the normal modes of oscillation which will be quantized in order to obtain photons are not the same as the normal modes of a free field in vacuum. That fundamentally changes the Dispersion relation of the wave function. We chose to call it a photon just the same, but that choice really is arbitrary since the two objects have fundamentally different natures and properties. Dauto (talk) 13:21, 22 August 2013 (UTC)

I imagine that a lot of people have wondered at this, having been told that we can only observe light travel at the same speed c, we are then told that it can “slow down” when travelling thru a medium. How is that possible? I think the simple answer is that when light is travelling, it cannot be seen to move at any other speed than c, regardless of whether it is moving through empty space or honey. When a photon moves thru material, it can be briefly trapped by an electron in an atom’s shells. That excites the atom as it absorbs the photon, and then the atom sheds the photon (or another exactly the same) and returns to its previous state of energy. This procedure takes some little time. The photon ALWAYS travels at the same speed, but if we count these times when it is being absorbed and re-emitted, then it appears to travel at a lower speed than c. Myles325a (talk) 07:49, 23 August 2013 (UTC)

The problem with that explanation is that it is completely wrong. There is no absorption and re-emission going on. What you do have is that the normal modes of vibration that are being quantized are different because the electrons also vibrate back and forth along with the electromagnetic fields and must be included in the proper calculations of the dispersion relation. A photon in a medium is partially a matter vibration phenomenon. We still call it a photon, but it is not the same thing as a photon propagating in vacuum. Dauto (talk) 19:04, 23 August 2013 (UTC)

Yeah, well that's what I said more or less, except in language that is not full of obscurantist voodoo talk..."Vibration phenomenon"? Next you will be talking about crystal power and auras and we will all be told to get coffee enemas. Not for this little black duck! I like my science neat and my coffee in a cup, thank you all the same. Myles325a (talk) 04:07, 24 August 2013 (UTC)

Not to be rude, but what are you talking about? I don't see any new agey junk science terms, nor anything obscurantist; it's a pretty clear answer about a complex phenomena. Moreover, if you look at the relevant section of Wiki's own article on photons, you see something to the same effect.Phoenixia1177 (talk) 03:59, 25 August 2013 (UTC)

Is there any organ that made of only one tissue?

Is there any organ that made of only ONE tissue? (I have not found information about on Wiki) 46.210.138.154 (talk) 17:48, 21 August 2013 (UTC)

Well, to get an absolutely solid answer you'd have to first explain what you mean by a "tissue", but using the common meaning I'd say no, because every organ contains blood vessels, which are a distinct type of tissue. Looie496 (talk) 18:37, 21 August 2013 (UTC)

what do you think about the nail or hair, are they not organs or do they contain blood vessels? 46.210.138.154 (talk) 18:46, 21 August 2013 (UTC)

I've never seen nails or hair referred to as organs. (I regard these kinds of things as totally unimportant -- I'm just giving my impression of how most people say things.) Looie496 (talk) 18:50, 21 August 2013 (UTC)

Would the heart not count as this, being entirely composed of cardiac muscle? --TammyMoet (talk) 21:26, 21 August 2013 (UTC)

Epicardium, cardiac muscle, fibrous pericardium, serous pericardium, .... Reaper Eternal (talk) 21:33, 21 August 2013 (UTC)

Liver? Count Iblis (talk) 23:26, 21 August 2013 (UTC)

Blood vessels, also bile ducts (arguably there's a common origin to that cell type, but they look really different under a scope, and heck, there's a common origin to every cell type...) Wnt (talk) 06:17, 22 August 2013 (UTC)

Hmmm, I suppose the lens of the eye is one tissue type ... but it's not really an organ. Wnt (talk) 06:21, 22 August 2013 (UTC)

"the lens of the eye is one tissue type".^{[citation needed]} Have a look (ha!) at Lens (anatomy)#Lens structure and function. DMacks (talk) 14:38, 22 August 2013 (UTC)

I'd argue that the lens fibers and lens epithelium are the "same tissue type" at different stages of differentiation. I mean, if we hold the same standard to the liver, then we say there are three different tissue types because there are zone I, zone II, zone III hepatocytes. But even that is probably an incomplete description of the levels of differentiation involved... ultimately every cell is unique, and to some extent or other all the differences matter. Wnt (talk) 20:18, 22 August 2013 (UTC)

Absorbtion of non-soluble medicine.

Can non-soluble medicine pills be absorbed into the body through the mouth? This applies to the whole world. Pubserv (talk) 17:59, 21 August 2013 (UTC)

Not unless they are broken down by saliva. Otherwise the pill would just sit there forever. Looie496 (talk) 18:41, 21 August 2013 (UTC)

I mean pills that turn into powder when you crush them. Pubserv (talk) 19:58, 21 August 2013 (UTC)

I'm not an expert in medicine, but there are medications that don't dissolve in water, but dissolve with fats. Vitamin D, while not really a medicine, is one of the cases. --Wirbelwind(ヴィルヴェルヴィント) 00:23, 22 August 2013 (UTC)

Also, solubility isn't a 100% yes or no thing. A material might not be very soluble in water, but several hours churning in the digestive system, with water, fats, and acid thrown into the mix, might tend to break it down rather effectively. For example, calcium carbonate, present in many antacid tablets, isn't very soluble in water, but will react with the acid in the stomach and dissolve that way. StuRat (talk) 08:19, 22 August 2013 (UTC)

nervus cells called neurons?

why all cells of the body are called "cyties" (in example: osteocyties is of bone tissue, miocyties is of muscle tissue) while the nerves cells called neurons without 'cyties'? and second, how are called the cells of connective tissue? (see about the names of the cells of the other tissues in the first qustion). thank you. 46.210.138.154 (talk) 18:40, 21 August 2013 (UTC)

The term is "cytes", not "cyties" (no "i"). It's simply a synonym for "cell". As to why neurons are not called "neurocytes", the answer is simply tradition. Looie496 (talk) 18:45, 21 August 2013 (UTC)

thank you for the answer on the first qustion. what about the second question on the name of the cells of the connective tissue? Is it called conneccytes? :) 46.210.138.154 (talk) 18:54, 21 August 2013 (UTC)

Fibrocytes and fibroblasts. Icek (talk) 19:35, 21 August 2013 (UTC)

Sorry, fibrocyte is just not the general name of the cells which incloud all the connective tissues. A fibrocyte is only ONE of kinds of the the cells which build the connective tissue. There are some kinds of cells of connective tissues like adipocyte, chondrocyte, endothelium, and so on. So, you can not say that the name of all cells of connective tissue called "fibrocytes" like you can say that the miocyte is general name of all kinds of muccels tissues cells. It's intresting for me to know if there is a general term for connective tissue cells. 176.13.166.201 (talk) 20:51, 21 August 2013 (UTC)

Why are you deliberately messing up the spelling of "muscle"? 89.241.229.123 (talk) 15:04, 24 August 2013 (UTC)

August 22

if Mars still have more greenhouse effect like Earth

Before I didn't think planetary atmosphere and compositions are important in determining habitable zone but my college professor told me planetary atmosphere and composition are important to determine where the habitable zone will be, so if Mars have more greenhouse effect and atmosphere pressure roughly same that of Earth will it be much warmer than it is now? If it will be warmer than what will the average planetary temperature be? 23 F? If Titan didn't have any greenhouse effect will Titan be even colder?--69.233.252.198 (talk) 02:14, 22 August 2013 (UTC)

To determine the final temperature you'd have to know exactly how much greenhouse effect there will be. Venus is an example of a runaway greenhouse effect. The gas giants also have a pronounced greenhouse effect, although there they may be heated more by internal sources (radioactive materials, tidal forces, etc.). StuRat (talk) 09:12, 22 August 2013 (UTC)

The OP's question about Mars reminds me of what Carl Sagan had to say about the possibility of terraforming Mars and Venus. For Mars, you have to create greenhouse effects somehow. For Venus, it's the opposite - you have to introduce something that will somehow consume greenhouse gases. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:20, 23 August 2013 (UTC)

The immediately obvious solution would be to funnel enough of the gas from Venus to Mars.... 86.141.186.4 (talk) 12:53, 23 August 2013 (UTC)

Sure, a flexible, stretchable conduit of some kind, hundreds of millions of miles long. That shouldn't be too difficult to engineer. Kind of like a gigantic siphoning hose. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:34, 23 August 2013 (UTC)

Wormhole X-Treme! --Stephan Schulz (talk) 14:39, 23 August 2013 (UTC)

Heh, he's got a point. There are a lot of things that aren't too difficult to engineer, it's just the building part that gets you. :) But at least in fantasy you could use an elaborate system of momentum exchange tethers to exchange small packets of mass between Mars and Venus with relatively small energy investment total. Wnt (talk) 18:49, 23 August 2013 (UTC)

Do how old scientific articles matter the accuracy of informations?

Thistold me the article I linked were published in 1993 [3] and 1997 (Once and Future of the Sun) and is not a recent document. Do how old the scientific paper is published matters how accurate the information gets. Then why didn't the previous editors repost what their works in 1993 when the newer informations came up? I didn't thought the published dates matters that much. Or these authors are not require to repost information when new informations come up. Do these authors change their mind when the newer evidence comes up? I thought if they have changed their mind they suppose to repost their works they done in their earlier studies.--69.233.252.198 (talk) 02:38, 22 August 2013 (UTC)

Yes how the information is published does matter to how accurate the information is or at least how much you can trust it. If it's published in a refereed journal it means that someone else, who also works in the same field, has read it and not found errors within it. While if it's just put up on the web without being refereed it may well be correct but the information hasn't been independently scrutinised. As for the age of a paper, for a start computers are a lot more powerful now so you can enter more information. So with the same data you can get more accurate answers. Also the structure of the Standard Model of the Sun has changed quite a bit since 1992 with the lunch of SOHO. For new information a new paper would be written, submitted, reviewed and published. The old paper would be untouched after publication (there is only one publication run).Dja1979 (talk) 03:08, 22 August 2013 (UTC)

This is a largely subjective matter. It depends on the field of science or mathematics you're talking about. For example, Lord Kelvin's paper entitled "On the Age of the Sun's Heat engages in discussion on whether something made of coal could possibly be producing that much heat! Yet papers written by the exact same guy about the laws of thermodynamics in the exact same year remain as entirely valid and useful references, even today. Some fields just move faster than others!

As Dja1979 points out - recent spacecraft missions are still revolutionizing our knowledge of the sun - and papers from just a decade ago are unlikely to be of much use. Scientists working in a particular field tend to have a good knowledge of how far back they can reasonably refer without picking up on outdated information.

SteveBaker (talk) 13:53, 22 August 2013 (UTC)

It depends on the study done and the assumptions made. Sometimes a paper from a century ago can be a true pleasure to read, and as relevant today as the day it was written. There are even rare cases in which an ancient publication is found which was more knowledgeable than modern sources on a point (see Ge Hong regarding artemisinin) Wnt (talk) 14:38, 22 August 2013 (UTC)

Absolutely. It's not so much a matter of age, but a matter of what, if anything, has changed the scientific community's understanding since then. Math is not a science (in my view), but the results of math papers from e.g. 1900s are just as true now as they were then. Even in science, many old papers can be valid and useful for decades. If the OP is interested in specific examples in a given field, we could try to provide suitable refs. Of course, many old papers are outdated, because their findings have either overturned or improved (especially in younger subfields of e.g. computer science or genetics). This is generally held to be a good thing: it is how our understanding progresses, and is built in to the prevailing philosophy of science, specifically, Karl Popper's principle of falsifiability. (My WP:OR is that most currently practicing scientists are implicitly proponents of the Popperian view, even if they don't know it by that name, or don't think about philosophy of science much.) SemanticMantis (talk) 16:32, 22 August 2013 (UTC)

How do I identify a new type of earthworm?

having been around for many years, raised on a farm, dug worms for fishing, and gardened forever, I have discovered a completely different kind of worm this past week. I live in northern Ohio and came accross an area which has a very strong and firm eartworm population of 3 to 4 inch red colored worms that go crazy when uncovered. They twist and turn rapidly, they are very hard to hold on to, and they move very fast. Their bodies are very firm almost like a snake and they flop all over the place. Diameter is large. They are really strong and not at all like the thousands of giant earthworms that I have encountered before. They can extend themselves like a regular earthworm but their ends are very pointed. Can someone tell me if this is an unusual worm and what it might be? — Preceding unsigned comment added by 184.59.176.230 (talk) 17:22, 22 August 2013 (UTC)

Any photos you can offer? I can't help you either way, but someone else might be able to if you have one. Mingmingla (talk) 18:15, 22 August 2013 (UTC)

Just a guess, maybe a red wiggler? As their name suggests, they are feisty, and if I recall correctly, they are rather firm. They prefer compost to ordinary dirt. Was anything else different about this patch of dirt? Also check for the characteristic putrid smell that red wigglers release when agitated. SemanticMantis (talk) 19:18, 22 August 2013 (UTC)

Getting a tattoo while tanned or burnt

My friend is plannning on getting a tattoo after a holiday in Spain. He likes to ta his skin and thinks getting a tattoo the week after will pose no problems. My logic is that this is a bad idea and could probably scar him if he gets sunburnt. Not to mention the chance of blistering and a longer healing time. Does anyone know anything on this matter? Thanks ツ Jenova20 ^(email) 18:16, 22 August 2013 (UTC)

Some would argue that this is a borderline medical advice request. I don't know anything about tattoos, and Googling produces conflicting advice from various sources. Bearing in mind the medical disclaimer we usually wheel out in such cases, I would suggest you persuade your friend to consult the tattoo artist he is intending to use, in advance of his holiday. A reputable professional will be happy to advise him. - Karenjc 22:57, 22 August 2013 (UTC)

Borderline maybe but it's a hypothetical. I was always told when i got sunburnt that you shouldn't scratch it. Someone getting a tattoo over sunburn and making the area bleed seems like it would at the least scar or cause issues with healing. I'm not looking for medical advice, i'm asking a hypothetical question and interested if anyone knows. Thanks ツ Jenova20 ^(email) 08:10, 23 August 2013 (UTC)

Your friend is thinking of getting a tattoo and you're asking if it's likely to cause a scar if his skin is sunburnt - in what sense is that a hypothetical question? Richerman (talk) 08:37, 23 August 2013 (UTC)

I suppose i didn't word that well. I'm not asking if he should get it done, i'm just asking if there are any issues or studies on sunburn and scarring, healing, etc, when the skin is scratched or damaged further while healing. I think there would be but the Sunburn article doesn't really mention skin damage other than cancer. It's hypothetical in the sense that i've made assumptions for a made up scenario. If we can't do that then every health question here should be tagged in this way as medical advice. In that way most health questions and topics on cancer or common ailments should be banned from here as medical advice. See the point I am making? Thanks ツ Jenova20 ^(email) 08:59, 23 August 2013 (UTC)

But you didn't ask about sunburn and skin damage in a general sense, you gave what sounded like a question about a very specific situation. You even include a time frame and a vacation place.Phoenixia1177 (talk) 09:56, 23 August 2013 (UTC)

Indeed. A hypothetical question would be "if someone with a recent suntan got a tattoo, could this cause any problems ?". Jenova20 (talk · contribs) gave too many specific details for their question to be treated as hypothetical. This question definitley looks like a request for Medical advice, and Karenjc (talk · contribs) has given the only response that we can in that situation. Gandalf61 (talk) 10:11, 23 August 2013 (UTC)

Never mind. Not that important ツ Jenova20 ^(email) 10:18, 23 August 2013 (UTC)

It's well established that the hepatitis-armed scribble artists who do these things are not part of the medical profession, so factors affecting the quality of their work are not medical advice. I imagine that even the slightest bit of actual sunburn would make their practice particularly unpleasant. But the aesthetic and practical issues are harder to judge. The practitioners deal with all shades and toughnesses of skin, usually, but if the thing is meant to be seen while tanned, would it help to do it while tanned? If not would it be improperly shaded for the lighter skin? I'm afraid my aesthetics is just don't: there must be 10,000 ugly marks for every one that isn't immediately unappealing. That's not an answer of course but it illustrates how hard an answer is. Wnt (talk) 18:44, 23 August 2013 (UTC)

I have a Toad in my house but I can't find him!!!

It was one of these guys!

Okay, so I'd just finished mowing the backyard, when I saw an Eastern American toad on my porch. Now, a lot of cold blooded things like to come up on my porch to get sun, lizards, toads, frogs, and insect you can imagine...so I usually just say hi and ignore them. Except...THIS ONE HOPPED IN THE HOUSE!!! I tried to catch it and put it back out but he got into the office. I searched everything, my boxes of cables, the papers on my desk, my cat's stomach, basically turned the whole place upside down...but I can't find him!!! I just know the poor little fellow will die of starvation or dehydration if I don't find him soon, is there anything I can do to lure him out? --Free Wales Now! what did I screw up?  18:38, 22 August 2013 (UTC)

Maybe make a toad home (google images here [4]), put in a moist sponge and hope it attracts the toad? I'd place one near where he was last seen, and another in the basement, if you have one. BTW, many toads, especially large ones, don't need much water on a daily basis, and only return to water to breed. So dehydration is not a big risk in the next few days, especially if you have a basement, which would also probably have toad food... SemanticMantis (talk) 19:13, 22 August 2013 (UTC)

It should be easier to hear and see him at night, since they're nocturnal. Might even try the same door it came in through. Like Mantis says, there's likely no immediate danger. Toads are generally much less susceptible to drying out than frogs, and cold-blooded animals don't starve so quickly. Cats generally hate the taste of toads, so I wouldn't look too hard into stomachs. A bit of damp grass may be tempting, if it's still there by tonight. InedibleHulk (talk) 19:34, August 22, 2013 (UTC)

They're pretty good at hiding. When I was a kid, one time my brother and sister and I were keeping a toad as a pet, in a cardboard box, and it escaped. For a couple of days we saw no evidence of it. But then in the middle of the night my dad got up to pee, went into the bathroom, turned on the light, looked into the toilet -- and there was the toad staring up at him. He made us get rid of it. Looie496 (talk) 22:04, 22 August 2013 (UTC)

Great story :) I hope the OP updates us if he finds it. SemanticMantis (talk) 01:40, 23 August 2013 (UTC)

In light of the above anecdote, might putting a pan of water someplace on the floor attract the toad? ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:31, 23 August 2013 (UTC)

Explanation for the acronym SWE

The phrase "SWE Stereo" appears on my television screen to reveal the audio utilized by a local TV station in their broadcast. The TV station is SLCCTV (Salt Lake Community College TV, channel 86-1701) located in SLC, UT. Directly below SWE Stereo is the resolution value "480i SD" (standard definition}. Thank you, Thomas J Tippett Tjtippett (talk) 19:10, 22 August 2013 (UTC)

Just a guess, but might it have something to do with Secondary Audio Programming? If you have an SAP button on your remote or set, try pressing it and see if you get Swedish. InedibleHulk (talk) 19:49, August 22, 2013 (UTC)

Another guess is it has something to do with this satellite terminal the station might use. Do you know if the station has any connection to the ABC 4 station? ABC is said to use this system. InedibleHulk (talk) 20:07, August 22, 2013 (UTC)

Effects of music while working & studying on performance

I listen to music several hours a day while studying (I'm a math student) and I wonder how much it affects my performances. Does the type of music (rhythmical/calm/powerful/..., vocal music or not, etc.) and genre (I hear mostly classical music and film soundtracks) matter? Thank you. 23:07, 22 August 2013 (UTC) — Preceding unsigned comment added by 84.109.248.221 (talk)

Mozart effect might be relevant. Googling "effect of background music" gave a few promising-looking links, including this (MS Word doc) on 'The effects of background music on learning, performance and behaviour' and this on 'The effect of background music and background noise on the task performance of introverts and extraverts'. AndrewWTaylor (talk) 08:35, 23 August 2013 (UTC)

I'm a high school teacher who moves around a bit between different schools. Just started in a new school for a four week stint. As usual, many students have asked if they could listen to music while they worked, insisting that they work better that way. (Some didn't ask, and DID listen. They won't any more.) Andrew - that study could be very useful. Might just print out that abstract for sharing with students. HiLo48 (talk) 09:28, 23 August 2013 (UTC)

It's a commons highschool science-fair project...comparing different styles of music (better students remember to analyze both style itself and alignment with subject's preference separately), different types of tasks, etc. It's rare that their background "research" consists of more than the popularized version of the Mozart effect--even if they cite the original study they obviously didn't read it--or any of the later publications strongly refuting the popular form. Sigh. DMacks (talk) 09:34, 23 August 2013 (UTC)

Temperature ranges of gas giant moons

When my teacher keeps telling me planetary composition, albedo, and atmosphere gases are also important to determine planet's and moon's surface temperature, I keep thinking these factors are not important. But Does the airless moon of gas giants have temperature ranges small or the global temperature of Jupiter, Saturn, Uranus' moon have wide temperature fluctuation between day and night. Enceladus (moon) Say the minimum surface temperature is 32 K and the maximum surface temperature is 145 K. I checked Europa (moon) it said the minimum surface temperature is 50 K and maximum surface temperature is about 125 K. --69.233.252.198 (talk) 23:12, 22 August 2013 (UTC)

You keep thinking the atmosphere is not important and keep being wrong. It's very important. To give you an idea, Earth's average surface temperature would be about 60 degrees Fahrenheit lower if the Earth didn't have an atmosphere. That's a significant change. Dauto (talk) 23:47, 22 August 2013 (UTC)

August 23

the shape of heart

What is the geometric shape of the heart? Can I say that the heart is a truncated cone? (I do not think it is a truncated cone that is not really like that) — Preceding unsigned comment added by 46.210.149.99 (talk) 00:18, 23 August 2013 (UTC)

Asked and Answered on the Maths Desk
The following discussion has been closed. Please do not modify it.
For what purpose? In what context? μηδείς (talk) 00:28, 23 August 2013 (UTC) Let's presume the context is the human heart. Why does the purpose matter? Perhaps it's so that the IP can make a Heart-Shaped Box. --Demiurge1000 (talk) 02:06, 23 August 2013 (UTC) Kind of like a softball that's been hit a few too many times. ←Baseball Bugs What's up, Doc? carrots→ 03:12, 23 August 2013 (UTC) Is softball played much in Israel? CambridgeBayWeather (talk) 04:55, 23 August 2013 (UTC) Nah, they play strictly hardball. ←Baseball Bugs What's up, Doc? carrots→ 06:01, 23 August 2013 (UTC)

Breathing

If I inhale a mixture of gases called air which is 78.09% nitrogen, 20.95% oxygen, 1 % water vapour, 0.93% argon, 0.039% carbon dioxide, what mixture of gases do I exhale? Th4n3r (talk) 10:48, 23 August 2013 (UTC)

Amongst other things, it'll depend on your species, how long you held the breath, and the various physical conditions of your body. 86.141.186.4 (talk) 12:49, 23 August 2013 (UTC)

It depends on a great number of factors. Googling "rest oxygen consumption" returns a number of sites that give the oxygen consumption of adults as around 5% of what's available. It's converted to an equal volume of carbon dioxide. On this basis, the exhaled air will be 78.1 % nitrogen, 19.9% oxygen, 1.09% carbon dioxide, 1% water vapour, and 0.93% argon. Note that what you breaqth out is little changed from what you breath in, which is why mouth to mouth rescusitation works. Anything that increases metabolic rate will increase the conversion of oxygen to carbon dioxide - digesting a meal, physical exercise, thinking hard. Reacting to enviromental conditions will also increase it - for example shivering when cold. If you increase your body rate by either eating to much and getting fat, or building up muscle mass by exercise, your metabolic load increases but your lung volume capacity does not. (If you are quite obese, you lung capacity may be reduced, making you breath harder even at rest) Hence an increase in body weight will increase the percentage conversion of oxygen to carbon dioxide. Note that 1% water vapour in air represents 100% relative humidity at temperatures lower than 16 C, but only 20% rel humidity at 40 C. At the higher temperatures within the human comfort range, the body looses small amounts of water vapour to expired air. 1.122.214.154 (talk) 13:07, 23 August 2013 (UTC)

Don't forget that the water content will also increase; there's a lot of wet surface area inside the lungs. (The number above corresponds to only about 45% humidity at 20°C.) TenOfAllTrades(talk) 13:35, 23 August 2013 (UTC)

As is evident, especially in the winter, or when exhaling onto a glass surface. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:29, 23 August 2013 (UTC)

Alternative classification of Carnivora

Since not all Carnivora are in fact obligate carnivores and some are omnivores, is there some better and common (possibly unique) feature among them? Perhaps some taxonomists have proposed something on that? Brandmeister^talk 10:58, 23 August 2013 (UTC)

I would venture to suggest: their descent and relatedness. Linnean taxonomy used to be based on an ad-hoc mixture of visually obvious physical similarities, which taken in aggregate gave clues to organisms' actual relatedness (and were sometimes ambiguous or misleading), but nowadays it uses the much more rigorous methods of Cladistics, and can be corroborated by direct genetic comparisons. Characteristics that specific groups might have largely or uniquely in common are handy aide-memoires, but not ultimately definitive, because Evolution (if you'll excuse the trope). {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 12:53, 23 August 2013 (UTC)

Yes, ultimately ancestry is the real basis of classification. Often there are physical features that are highly characteristic, but they may not be obvious -- for example the layout of the teeth is often one of the most informative things. So is the bone structure of the foot. I don't know enough about this group to say anything specific, though. Looie496 (talk) 14:59, 23 August 2013 (UTC)

Yes, not all Carnivorans are obligate carnivores -- so what? As Carnivora indicates, the extant Carnivorans form a monophyletic group, which is about as good as it gets for modern cladistics/systematics. I'm not sure what feature they would all share, because the pinnipeds are a rather different from the rest. Perhaps there is some shared skeletal feature, but it would be pretty opaque to a non-specialist. As .195 says above, what they share is common descent. Conceivably, we could change the name to "Foofles", while keeping all members the same, but that would cause its own headaches. The way the International_Code_of_Zoological_Nomenclature works, names should follow the Principle of priority, unless there is some other good reason to change them (e.g. splitting an old paraphyletic group into two or more new monophyletic ones). Finally, beware the etymological fallacy! Hope that helps, SemanticMantis (talk) 15:03, 23 August 2013 (UTC)

That is, in my opinion, naming that order because of dietary habits is problematic (and, possibly, in other cases too): several non-carnivorans also prey and eat meat as their staple food, thus also being eligible for the name Carnivora. Just found a source, which says in particular: "carnivorans never develop shearing dentition beyond the original P4/mi carnassial pair, and this combination of shearing and grinding dentition has served Carnivora well". Perhaps the International Commission on Zoological Nomenclature will someday reconsider :) Brandmeister^talk 17:51, 23 August 2013 (UTC)

I understand your objection to Carnivora, but it is actually very common for things to work out this way. It's just what happens when we prefer original names, but also want to use modern tools to make clades as large and inclusive as they can correctly be made. Does it bother you that not all hemiptera have "half-wings"? Or that not all Orthoptera have "straight wings"? It's a terrible system, but it's the best we've got :) SemanticMantis (talk) 18:15, 23 August 2013 (UTC)

• See etymological fallacy. Come back if you have some questions about the relevance of that article to this problem. --Jayron32 14:56, 24 August 2013 (UTC)

Enemy locked onto heat signature; release flares

In the game Battlefield 3, one mission requires the player to occupy the gunner position in some sort of fighter aircraft. When the enemy locks onto the heat signature, a system of the aircraft occupied by the player warns the player and warns further when a missile is fired. The player is expected to release flares to thwart the enemy missile. How does the system recognise that the enemy aircraft has locked onto the heat signature? --89.241.229.123 (talk) 14:14, 23 August 2013 (UTC)

By what method does the attacker "lock on"? If it's via radio waves, those waves could be detected by the target vehicle's systems. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:28, 23 August 2013 (UTC)

Is the question about how the video game software operates this feature, or how its real-world counterpart works? Video games tend to use "omniscient software" that is aware of enemy moves, which simplifies the design and allows the creators to provide the desired user-experience.

In real life, a heat-seeking missile is not easy to detect. Because infrared missiles uses passive homing, they don't broadcast any type of strong signal. So the defending aircraft must use its own active RADAR to detect an unidentified object in the area; its onboard computer must calculate a trajectory and identify it as a potential missile; and then by deduction, it can be assumed to be a heat-seeker if it satisfies certain characteristics (size, velocity, RADAR signature - or lack thereof). This is an estimation problem that is prone to error and misidentification. Electronic warfare aircraft may escort fighter-aircraft in combat; these special airplanes carry more and better RADARs and computers (and other instruments) to help reduce error. Modern air doctrine emphasizes "Coordinated Command and Control" - enabling multiple airplanes, as well as ground and satellite facilities, to share combat information in real time, to help reduce errors in identification of unknown targets. Nimur (talk) 14:43, 23 August 2013 (UTC)

Here's a link to a Missile Launch Detector that Lockheed Martin makes [5]. It's a bit hard to tell, but it seems to work by detecting the IR flash of missile launch and then tracking the hot exhaust during flight. This discusses, briefly, the large dust and smoke plume from a Surface-to-air missile. Neither of these detection methods will work with a passive IR guided missile until the missile launches.Tobyc75 (talk) 18:18, 23 August 2013 (UTC)

Is there any condition in which two vectors can be divided?

Is there any condition in which two vectors can be divided? Concepts of Physics (talk) 14:52, 23 August 2013 (UTC)

This is not a common terminology for any commonplace operation in engineering or physics. You can define many mathematical operators that have qualitative similarities to division and accept vectors as inputs. But most people who use those operations prefer to use a different, more precise term, like computing an inverse or left-multiplication by the adjoint matrix. Nimur (talk) 14:57, 23 August 2013 (UTC)

This was discussed at length a month ago. Red Act (talk) 15:04, 23 August 2013 (UTC)

This page shows division of two vectors. Is this method correct? Concepts of Physics (talk) 15:28, 23 August 2013 (UTC)

That is a correct example for R (programming language) where the term "vector" is understood to be a one-dimensional array and where division is done element by element. This is a different use of "vector" than Vector (mathematics and physics). -- 200.7.90.57 (talk) 15:52, 23 August 2013 (UTC)

Division is the inverse of multiplication, so before answering that question you must chose some kind of multiplication to invert. The most common multiplication methods for vector dot product and cross product cannot be inverted. Dauto (talk) 18:20, 23 August 2013 (UTC)

If you want a fancy name for the operation described by 200.7.90.57, try Hadamard product. --Wrongfilter (talk) 21:05, 23 August 2013 (UTC)

Gap spanners on the International Space Station

What are the "gap spanners" that I read about astronauts installing on the International Space Station? The best I can find is that they are "used by spacewalkers to get from one module to another", but I can't find any details. Are they cables? Are they rods? What are they made out of? How are they attached? Are there any good photos of them online? -- 200.7.90.57 (talk) 15:30, 23 August 2013 (UTC)

Astronaut Jerry L. Ross, who flew on STS-88, explains gap spanners in this crew interview, available from spaceflight.nasa.gov:

“ Because the Unity node is so large in diameter we couldn't mount all the hardware on the outside of its structure that we wanted to, while it was still in the payload bay of the orbiter, and the launch environment that exists there. So, Jim and I will be installing a series of additional handrails, or handholds, on the outside of the station which we'll need for tasks, either on our flight or future ones. We'll also be putting some additional foot restraint sockets on the outside of the structure that we can plug our foot restraints into to do tasks on this EVA as well as others. We have a thing called a gap spanner, which is really nothing more than a long piece of strap that we're going to attach between a couple of handholds and cinch tight. That is a way of bridging a gap that was too long between handholds to provide a continuous translation path for crewmembers to operate on the station. ”

So, it seems like a gap spanner is a pretty mundane piece of cloth... until you realize that it's a festering breeding ground for orbital space-fungus! Here's a very high resolution photo from the same page of a ground technician swabbing the fungus off a gap spanner. Nothing is mundane or routine in manned space flight! Nimur (talk) 14:24, 24 August 2013 (UTC)

Thank you, Nimur. You're my hero! -- 200.7.90.57 (talk) 15:39, 24 August 2013 (UTC)

the haert rate in different bodies sizes

What is the reason that the big body is with low heart rate and a small body is with high heart rate? In example: addult from 10 years and above has heart rate of 60-100 per minute while an infant (until 90 days) has heart rate of 80-205 per minute! The same things are in animals. In example: the elphent has 25 HR per minut while the mouse has about 500 heart rate per minuts! So, in short: Why does as much as the body smaller the heart has high heart rate? 95.35.239.134 (talk) 16:36, 23 August 2013 (UTC)

It's partially related to one's activities. Many small animals are much more active than big ones, as such they require higher physical performance (particularly, better oxygen supply) which in turn requires high heart rate. Mice in particular are constantly vigilant to avoid predators, requiring higher physical performance and as such high heart rate. Brandmeister^talk 18:08, 23 August 2013 (UTC)

All right on mice you can say that they are active, but what do you say about babies compared to children? Children more active and yet they have only 60-100 beats per minute compared to babies who sleep most of the day and have between 85 -205 beats per minute.95.35.239.134 (talk) 19:56, 23 August 2013 (UTC)

My guess is that the size of the heart is also important, as a bigger heart can of course pump more blood than a smaller one if both were pumping at a similar speed. Since blood flow is limited by the elasticity of the blood vessels, I'm guessing a big heart pumping very quickly could create too much pressure and rupture the veins, especially if the diameter of the various types of veins does not increase proportionally to the size of the heart. I'm unable to confirm my guesses with reliable sources at the moment, however. Effovex (talk) 20:11, 23 August 2013 (UTC)

The typical operating speed (and presumably the most efficient speed) of mechanical devices, such as pumps, motors, and engines, trends to be inversely proportional to their size. Perhaps someone here with a mechanical engineering background can speak to this point. -- 200.7.90.57 (talk) 20:37, 23 August 2013 (UTC)

Indeed, though the reasons are somewhat different. The heart pumps by successive contractions. That means that at every beat it accelerates a small quantity of blood, which then gets decelerated in the blood vessels. The kinetic energy imparted to the blood depends on the ex-chamber spurt time, and the stroke/spurt distance. In a small animal the stroke distance (which is proportional to the length and to the width of the heart) is less, so to impart the same kinetic energy per unit volume of blood, and thus get the same blood velocity, the time per beat must be shortened. In animals of all sizes, the required blood velocity is much the same, as it is set by capilary wall thickness, gas and nutrient diffusion range, and tissue requirements. 1.122.171.86 (talk) 00:36, 24 August 2013 (UTC)

survive in a space station without air renewal

Suppose you are in the International Space Station, with destroyed air renewal systems and no other sources of oxygen.

You have plenty of food and water (but you cannot use it to produce oxygen). At the beginning the air is fresh.

How long can you survive there? Months? --Blacknight87 (talk) 17:27, 23 August 2013 (UTC)

Several days, certainly not reaching one month, I think (around one week at best) until the buildup of carbon dioxide reaches critical point. To extend the survival period it's possible to isolate every room by sealing hatch or whatever and once the CO2 level in one room reaches uncomfortable point, move to another. But still there should be some emergency backup system out there. Brandmeister^talk

There are Oxygen candles in the ISS. CO2 is usually deadly at about 10%. A human produces about 1 kg of CO2 a day. The molar mass of CO2 is 44 g, so 1 kg is about 23 moles or about 500 l of CO2 under normal condition. The ISS has a pressurized volume of 837 m³. So 10% concentration should be reached in 160 (person-)days. That is a lot longer than I would have expected. --Stephan Schulz (talk) 18:33, 23 August 2013 (UTC)

But is it enough oxygen for 160 days? --Zhitelew (talk) 18:57, 23 August 2013 (UTC)

Since one molecule of O2 makes one molecule of CO2, and both gasses have more-or-less (for small values of less!) the same volume under normal conditions, yes. Unless I made a stupid mistake ;-). --Stephan Schulz (talk) 19:40, 23 August 2013 (UTC)

I suspect that that 10% figure is rather too high. NIOSH (CDC) puts the IDLH level at 4% [6], noting that it produces symptoms of intoxication within 30 minutes at 5%, and unconsciousness after a few minutes at 7%. A study on submariners reported that extended exposure to 3% CO2 produced only mild symptoms, provided sufficient oxygen was provided. Using a more realistic 4% threshold, the lone astronaut on the ISS is good for perhaps 60 days—assuming that there are no other chemical or biochemical processes on board that produce additional carbon dioxide..... TenOfAllTrades(talk) 23:22, 23 August 2013 (UTC)

To look at it from another direction, the Lunar Excursion Module (LEM) on the ill-fated Apollo 13 mission had an internal volume of 6.7 cubic meters...less than 1% of the internal volume of the ISS. The oxygen and CO2 removal provided in the LEM was intended to be enough for 72 man/hours (2 men, one and a half days) - and had to suffice for 288 man/hours (three men, four days) to get the crew safely home. Notably, they didn't run even close to being short of oxygen - but when the CO2 removal system was rapidly overwhelmed, they ran to the brink of CO2 poisoning until the famous "square peg into a round hole" fix was developed. But you can see that even with only 1% of the volume, it took a considerable amount of time for the extra astronaut to overwhelm the LEM's filters to the point of danger. With over 100 times as much volume, that would take 100 times a long. This suggests that (a) Oxygen deprivation would not be an issue - CO2 would be the major problem and (b) that User:Stephan Schulz's calculations are probably about right. SteveBaker (talk) 21:16, 23 August 2013 (UTC)

Part of the reason why the CO2 level rose so 'slowly' in the LM was that the scrubber unit wasn't fully exhausted. As the scrubber gets to the end of its lifetime, the particles of lithium hydroxide in the canister acquire a coating of lithium carbonate, making them much less efficient absorbers of CO2 (as the gas has to diffuse through the inert carbonate to get to the active hydroxide). While the scrubber canister would normally be replaced at that point, if one is willing to tolerate an elevated partial pressure of CO2 in the cabin then one can run the canister much closer to exhaustion—let those little particles marinate in more concentrated CO2, consuming the lithium hydroxide more completely and absorbing more CO2 before their retirement.

In the case of the LM, its original canisters had a design capacity for efficient scrubbing of 60 man-hours, but could remain in service for twice that time at a cost of higher ambient CO2 levels if absolutely necessary. (On Apollo 13, they ran for 107 man-hours before the CM units could be connected.) In addition, there was a spare unit good for another 40 man-hours of normal use (80 man-hours in an emergency) if the square-peg-round-hole fix took longer than anticipated. [7] If the scrubbers were completely gone, using the 1 kg per day per person round figure Stephan employed above, the lunar module would have been out of luck in less than half a day. TenOfAllTrades(talk) 23:11, 23 August 2013 (UTC)

Do they have suicide pills on board so they don't have to suffocate to death? How long /would/ they last if the zombie apocalypse suddenly happened or something? Is it CO2 poisoning or is there something else needed from the ground that must happen before the air runs out? 108.27.81.195 (talk) 00:56, 24 August 2013 (UTC)

Under normal conditions, they keep a Soyuz capsule docked on the station that can be used as an emergency return vehicle if necessary. Assuming conditions on the Earth's surface are survivable there is a good chance that the crew would attempt to return to Earth before they ran out of air. However, I'm not entirely sure how easy or difficult it would be to manage a reentry if ground control had been destroyed. Dragons flight (talk) 04:23, 24 August 2013 (UTC)

Femininity facial analysis?

The Bradley/Chelsea Manning story has me wondering: with all the fancy facial recognition software, and research into reactions people have toward averaged faces, is there a program available that can analyze "femininity" in a face, either from a 2D picture or in person/3D? To me Manning's face always seemed a little bit female, and I was wondering if that is quantifiable. If so, does it actually predict some increase in odds of being transgendered or gay? Wnt (talk) 18:59, 23 August 2013 (UTC)

Here's a good list of refs, 101 of them about determining/sex gender of human faces via computer vision algorithms [8] (search is articles related to a seemingly influential paper on the topic [9]). There seems to have been a boom in the 1990-2006 range, but it's still being researched at a steady pace. It looks like even 10 year old routines can discriminate about as well as humans (~90% accuracy, hair removed or hidden), using things like support vector machines. Two articles jumped out as highly relevant to your question: "What's the difference between men and women? Evidence from facial measurement" [10], and "Boosting Sex Identification Performance" [11]. Some of these papers might have code online as supplementary material, or allow a (sufficiently savvy) reader to implement the algorithm. I didn't look for "off the shelf" software. SemanticMantis (talk) 21:01, 23 August 2013 (UTC)

Well, how does one DEFINE femininity? Seems to me like this is a highly subjective thing to evaluate. 24.23.196.85 (talk) 01:07, 24 August 2013 (UTC)

How about with science, like SemanticMantis demonstrated with references and logic, and a surprisng lack of caps. Shadowjams (talk) 06:05, 24 August 2013 (UTC)

Yes, defining femininity is problematic. Note also that the papers are mostly about determining sex, not gender. In this case "female-ness" might be a better word than femininity, when discussion how computer algorithms score faces. SemanticMantis (talk) 14:24, 24 August 2013 (UTC)

Geology/Pleistocene/CLIMAP

During the 1970's, CLIMAP was created to draw a map of the world at the time of the glacial maximum, 13Kya, (or is it earlier?). Where can I find that map and where can I find maps of North America between then and now. I have a particular interest in Lake Bonneville and Lake Agassiz.Bobgustafson1 (talk) 19:19, 23 August 2013 (UTC)

You might start with out article on CLIMAP: Climate: Long range Investigation, Mapping, and Prediction. It contains a reference to "CLIMAP (1981). Seasonal reconstructions of the Earth’s surface at the last glacial maximum in Map Series, Technical Report MC-36. Boulder, Colorado: Geological Society of America.", which probably provides many more details, though you'd probably need a good research library to find that book. However, it would be a mistake to think of CLIMAP as aiming to "draw a map". Rather it was a collection of related research projects to document conditions as they existed on Earth about ~18 kya. There would be many maps, some regional, some global, each reflecting or summarizing different parts of the investigation. In addition, other results of the related studies are probably scattered through various academic journals from that time period. Since you asked, reading about Lake Agassiz and Lake Bonneville might also be useful. My impression though is that our understanding of Lake Agassiz and its changes through time have improved greatly since the 70s, so you might want to look at more recent reviews. Dragons flight (talk) 20:14, 23 August 2013 (UTC)

Adults

Do mle adults have XY chromosomes and female adult humans have XX chromosomes? If so, is it possible to change theses chromosomes? Pass a Method talk 22:07, 23 August 2013 (UTC)

See biological sex, gender, sex chromosomes, XY sex-determination system, aneuploidy, sex differences in humans. The short answer to the first question is "mostly". The short answer to the second is "no". 86.163.2.116 (talk) 22:17, 23 August 2013 (UTC)

Yes: mostly; no. See also, incomplete penetration. μηδείς (talk) 04:54, 24 August 2013 (UTC)

August 24

World's biggest skyscraper

What's the world's biggest skyscraper by basically, uh, how big it is, that is the volume enclosed by the outside walls? I wonder how Shanghai Tower stacks up. 108.27.81.195 (talk) 00:45, 24 August 2013 (UTC)

See List of tallest buildings. Dismas|^(talk) 00:54, 24 August 2013 (UTC)

I think 108 IP is asking about the biggest building by VOLUME, not height. But I have no idea where to get this info -- can someone help? 24.23.196.85 (talk) 01:06, 24 August 2013 (UTC)

See List of largest buildings in the world, which answers that very question. WHAAOE. --Jayron32 01:07, 24 August 2013 (UTC)

Bah! I was close. Was getting called away to something else while replying, so I didn't get a chance to double check. Dismas|^(talk) 01:11, 24 August 2013 (UTC)

The Boeing building is by far the largest building by volume, but it's not much of a skyscraper. The two lists linked here would need to intersect. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:52, 24 August 2013 (UTC)

I believe there's a Wikipedia tool for that (in fact, I used it not too long ago to look for movies set in London during certain time periods -- you just enter "Films set in London" and, say, "Films set during the 1940s", or in your case, "Largest buildings" and "Tallest buildings") -- does anyone remember what's this tool called? 24.23.196.85 (talk) 04:08, 24 August 2013 (UTC)

Are you perhaps thinking of WP:CATSCAN? Dismas|^(talk) 04:10, 24 August 2013 (UTC)

Yep, that's the one! Thanks! 24.23.196.85 (talk) 04:14, 24 August 2013 (UTC)

Strongest known tornado outside of the United States; A question about the Fujita scale

I searched for this both online and in Wikipedia articles, but I could not find the answer. Basically, what is the strongest known or recorded tornado (in terms of intensity) outside of the United States? As a side question (although related), are either the Fujita scale or the Enhanced Fujita scale outside of the United States and Canada? Narutolovehinata5 ^tccsdnew 03:54, 24 August 2013 (UTC)

The article List of F5 and EF5 tornadoes has seven entries from Europe - see also List of European tornadoes and tornado outbreaks, List of Asian tornadoes and tornado outbreaks and List of Southern Hemisphere tornadoes and tornado outbreaks, although those articles generally don't have the intensities listed. The Enhanced Fujita scale is based on damage to typical American structures ("Manufactured Home – Double Wide", "Large, Isolated Retail Building [K-Mart, Wal-Mart]"), so I don't believe it's used outside the USA and Canada - our article doesn't say otherwise. Tevildo (talk) 11:53, 24 August 2013 (UTC)

According to this website, there were two strongest tornadoes in Europe, both T10-T11 on TORRO scale (one struck France on 19 August 1845 and the other one Italy on 24 July 1930). In terms of deaths the strongest one seems to be Daulatpur–Saturia tornado. Brandmeister^talk 13:57, 24 August 2013 (UTC)

Astigmatisms and autostereograms

I'm looking for solid references (preferably ones that pass WP:MEDRS) discussing astigmatisms and autostereograms, but so far all I've found are forums and similarly unreliable sites at which people chat about the subject. Basically looking for something explaining the effects (or lack thereof) of astigmatisms on astigmatics' ability to "do" autostereograms, but something talking about other aspects of the process of "doing" autostereograms for astigmatics would be helpful. A little context, in case that help — I've been trying fruitlessly to teach an astigmatic acquaintance how to "do" autostereograms, and I'd like to know if the literature suggests that it's impossible/harder/no different/whatever. Nyttend (talk) 12:38, 24 August 2013 (UTC)

What scientific problems have been proven impossible to determine?

--121.7.36.13 (talk) 13:12, 24 August 2013 (UTC)

None (by definition). Dauto (talk) 13:52, 24 August 2013 (UTC)

Science does not deal in absolutes like proofs. We can prove scientific facts only ever with respect to a given theory, and support for a scientific theory is always tentative in principle (although what a scientist considers "tentative" is often more certain than what we consider "facts" in everyday life). There are a number of problems in math (including theoretical computer science, mathematical logic, and similar disciplines) that are proven to be impossible to answer in general. Examples include the Halting problem, the Post correspondence problem, and the Entscheidungsproblem. --Stephan Schulz (talk) 13:56, 24 August 2013 (UTC)

Even proving you can't for instance solve the halting problem doesn't mean there can't be an oracle machine that always gives the correct answer. It is very highly improbable though! Dmcq (talk) 14:33, 24 August 2013 (UTC)

There are many concepts which seem, at first glance, to be simple to the uninitiated which are, not merely difficult to prove, but actually proven to be impossible to determine. Many of the concepts surrounding "quantum" fields are governed by the Uncertainty principle, for example, which doesn't merely state that somethings are outside our current technological grasp of determining, but that they are physically impossible to determine, for example certain pairs of properties, such as momentum and position, are impossible to know simultaneously for any sufficiently small particle. --Jayron32 14:54, 24 August 2013 (UTC)

No - the proof relating to the halting problem doesn't say that you can't solve it - only that a Turing Engine can't solve it. I could disagree though that the halting problem "has proven impossible to determine" though - we've looked at it - and we are 100% sure that you cannot write a computer program that looks at another computer program and tells you whether that program will halt or not. This isn't some kind of mysterious unsolved problem - it's that we have total and complete certainty that some particular determination cannot be made. It's like the laws of thermodynamics say that you can't make a perpetual motion machine - or that the uncertainty principle says that you can't simultaneously know the position and momentum of an electron - or that godels' theorem shows that there exist some class of mathematical theorems that can never be proved or disproved.

I think we should help the OP to refine the question a bit. There are many areas of doubt to consider:

1. Some things we know for 100% certainty cannot ever exist: A Perpetual motion machine or a computer program that can tell whether other computer programs will eventually halt or not, an engine that'll propel a spacecraft at the speed of light...that kind of thing. It's not just that we haven't discovered a way to make these things - it's that we know for 100% sure that they are impossible.
2. Some things we know for 100% certainty we cannot ever measure: The nature of light from a star that lies outside of the observable universe, the exact position and momentum of an electron. These are fundamentally unknowable things.
3. Some things we definitely don't know - but might one day know: What is dark matter? What caused the first living thing to appear on earth? More research is needed - but we can probably work out the answer somehow.
4. Some things are reasonably well known but not with sufficient accuracy: Are there planets orbiting other stars that are habitable by humans? (Almost certainly - but maybe not.) How much temperature rise will we experience if we continue to dump CO2 into the atmosphere at present rates? (Definitely too much...but we don't know exactly how much too much.)
5. Some things that we expect to be true but cannot yet prove: Can every even integer greater than 2 be expressed as the sum of two primes? (We're pretty sure that the answer is "Yes" - but we can't yet prove it.)
6. Some things that we thought were probably true for the longest time - but were finally disproved: Euler's sum of powers conjecture, for example.
7. Some things that nearly everyone thought were false for the longest time - but were finally proven true: Continental drift, for example.
8. Some things that we thought were true - but are only approximately true - or are only true in special cases: Newton's laws of motion, for example.
9. Some things are "unfalsifiable" - we can never prove them false, but they might one day turn out to be proven true: The existence of God, The "simulation hypothesis", for example.
10. Some pairs of ideas that both seem to be "proven" true - but are contradictory in nature so either we're missing something, or one or both of them must actually be slightly incorrect: Gravity and Quantum Theory, for example. Gravitational theory works great at large scales and Quantum theory works great at small scales - but when the two intersect (eg at the boundary of a black hole), they predict different outcomes - so we know there is a problem somewhere.
11. Some things that many non-scientists THINK scientists have trouble with - but which are actually well understood: How come a bee can fly with wings that seem to be too small? (Wingtip vortices are exploited by bees in a way that was not obvious to one writer - and everyone took that as "Scientists say that bees can't fly - look how stupid scientists are!")

I'm sure there are other categories of doubt and error that I haven't thought of...but to find concrete examples, our OP needs to be much more specific. SteveBaker (talk) 15:28, 24 August 2013 (UTC)