Wikipedia:Reference desk/Archives/Science/2014 July 12

= July 12 =

Sleeping kitties


Why do cats habitually sleep in this position? I've only ever heard one explanation: that it's the result of the same factors that cause Earth and water droplets to become spheres, which seemingly is isoperimetric inequality. This doesn't make sense to me, however: a cat is quite able to control itself, unlike the inanimate water droplets (thus it's not forced simply by gravity or surface tension), and yet it still adopts this position instead of stretching out in a linear shape. Nyttend (talk) 05:18, 12 July 2014 (UTC)


 * I have a shitload of cats, and have seen all the varieties of positions a Google Image search shows. Just a matter of comfort and preference, I think, like why humans or dogs toss and turn. Sometimes one way feels good on the back or legs, but then they get stiff or sore or hot. Boring old gravity is the most compelling force here. InedibleHulk (talk) 05:48, 12 July 2014 (UTC)
 * Small correction: I've never seen a cat sleep like this. Thanks, Google. InedibleHulk (talk) 05:54, 12 July 2014 (UTC)
 * WARNING: This cat looks like a mouse. It's probably best you don't see it. InedibleHulk (talk) 06:03, 12 July 2014 (UTC)
 * Until a couple months ago, I had 7 cats. Would that be considered a shitload?  Dismas |(talk) 08:09, 12 July 2014 (UTC)
 * That's barely a fart in a snowstorm, by my measuring stick. InedibleHulk (talk) 09:44, 12 July 2014 (UTC)
 * I'd be more inclined to believe it's to stay warm rather than any gravitational reason. Out of all 6 of my cats, the 17 year old cat sleeps like that most often though not when her arthritis is bothering her.  Due to her age, I would think it would keep her warmer.  But like I said, when she's feeling stiff, she lays in a straighter position.  This being a reference desk though, I'll supply this which is from a blog but it's from a pet food company, so they may know what they're talking about.  It basically confirms the warmth aspect but also mentions their roots as den dwelling creatures and sleeping in confined spaces.  Dismas |(talk) 08:09, 12 July 2014 (UTC)


 * Cats will get into a position where they feel most comfortable. If it's warm, they'll extend their paws in order to expose the pads and cool off. If it's cold, they'll curl up into a fairly snug circle, typically with tip of tail near face. I've also seen a given cat sleep on either left or right side. It seems to depend on whim. ←Baseball Bugs What's up, Doc? carrots→ 09:31, 12 July 2014 (UTC)


 * Aaaah whim away, a whim away, :o) --Cookatoo.ergo.ZooM (talk) 11:27, 12 July 2014 (UTC)


 * To be clearer, I meant gravity causes the stiffness and soreness that necessitate getting comfortable in the first place. And why it's harder to lay in certain positions. It's a weak force, in a way. InedibleHulk (talk) 09:46, 12 July 2014 (UTC)
 * Not exactly; the Weak force is completely different. Nyttend (talk) 13:17, 12 July 2014 (UTC)
 * Yeah, that's one of the few science things I remember. Just a (rather lame) play on words. InedibleHulk (talk) 01:01, 13 July 2014 (UTC)
 * Yes, but gravity is a weak force, even compared to the weak force. It is only as important as it is because it operates at an infinite distance and operates with the same positive sign on all matter; that is, matter and anti-matter both have positive mass.  Robert McClenon (talk) 01:10, 13 July 2014 (UTC)
 * Hadn't thought of it like that. But yeah, those are pretty important quirks. Thanks for sharing. Now you've got me comparing the forces. Interesting, but annoying. Each time I learn how two aspects are different, I start wondering why. "Why?" is also an infinite loop, and works whether the topic matters or not. Probably why there's a Y at the outer boundary of "gravity". Or not. All I know is I only meant gravity isn't stretching that cat. Just strongly suggesting it turn itself. InedibleHulk (talk) 04:31, 13 July 2014 (UTC)
 * In my experience many other mammals (rats, mice, hamsters, dormice, ferrets, marmosets etc.) sleep curled up too. Although I think it is mainly to keep the exposed surface area as small as possible to keep warm, I suspect it is also for protection from predators. If you were being attacked and couldn't run away you would instinctively try to curl up into a ball to protect the softer parts of your body and your vital organs. Richerman    (talk) 09:53, 12 July 2014 (UTC)


 * I'd go with the protection from predators idea, but more to stay hidden than to protect themselves. Fawns are also known for curling up to hide from predators. StuRat (talk) 13:40, 12 July 2014 (UTC)


 * In my experience, the position a cat adopts is a complex calculation which includes factors such as how much of its body can be put into sunlight and how uncomfortable it can make any sleeping humans around it. Supplementary factors may include making the belly or back available for rubbing. Matt Deres (talk) 12:07, 12 July 2014 (UTC)


 * See fetal position. I agree with the reasons above, such as conservation of heat.  Also note that cats have a far more flexible spine than humans, so such a position is not as uncomfortable as it would be for a person curled up in that position for an extended period.


 * Another reason has to do with their fur and bedding material. Many furry animals will move in a circle as they lie down, to assure that all their fur is lying flat and the bedding material (grass, etc.) is evenly distributed.  That position is the end product of such movements.  StuRat (talk) 13:45, 12 July 2014 (UTC)


 * My two year old kitten often sleeps on our bed belly up with all paws stretched out to the limit. It is a very funny picture to see her sleeping this way. --AboutFace 22 (talk) 15:33, 12 July 2014 (UTC)


 * Is it warm in that room ? That's the classic "feline air conditioning"  pose, to cool them down. StuRat (talk) 15:37, 12 July 2014 (UTC)


 * My wife just said: 77-78F in the summer, 73-74F in the winter. It is our bedroom and the cat jumps on our bed. --AboutFace 22 (talk) 20:53, 12 July 2014 (UTC)


 * Yea, that summer temp is a bit warm, if you happen to be wearing a fur coat, but nothing the old feline A/C can't fix. StuRat (talk) 05:08, 13 July 2014 (UTC)

Condoms
Do condoms have some kind of anti microbe on them? 90.192.101.145 (talk) 10:39, 12 July 2014 (UTC)
 * Not usually. Some condoms have Nonoxynol-9 to act as a spermicide, but (as far as I know) none are sold with an antimicrobial lubricant.  See Condom for our article. Tevildo (talk) 11:43, 12 July 2014 (UTC)
 * The term microbe encompasses a diverse range of organisms, some of which are important to human health. Condoms are ideally sterile and have no additives that can upset Vaginal flora. Sexual intercourse with a condom appears to change lactobacilli levels, and increases the level of Escherichia coli within the vaginal flora. Disruption of vaginal flora can lead to infections such as vaginal candidiasis or bacterial vaginosis (BV). Nonoxynol-9 spermicide may have side effects and has been withdrawn by some manufacturers. 84.209.89.214 (talk) 12:52, 12 July 2014 (UTC)

High index lenses
Is there a way you can tell between a standard index and high index lens for glasses just by looking at them? 82.132.212.22 (talk) 11:33, 12 July 2014 (UTC)
 * For a given lens power, a standard lens will be much thicker than a high-index lens. If a pair of glasses has thick lenses, they're very likely to be standard index, high power lenses.  However, a pair with thin lenses may be standard index, low power or high index, high power.  If you get to look through, as well as at, the glasses, you can estimate the power and judge the index accordingly.  See Corrective lens for our article.  Tevildo (talk) 11:49, 12 July 2014 (UTC)
 * If there is no anti-reflective coating, the reflectivity of the material is closely related to the refractive index. This would allow someone familiar with gauging reflectivity to distinguish. The high reflectivity of high-index lenses is also why anti-reflective coatings are very common on high-index lenses. Someone familiar with the specific coatings may be able to distinguish coatings (often by their colour), and since coating materials are often determined by the refractive index of the lens, this will give a clue to the index of the lens. So, yes, someone with experience can probably tell just by looking at the reflection intensity and colour. —Quondum 14:02, 12 July 2014 (UTC)

Rows of transition metals
Does "fourth-row transition metal" mean the transition metals of period 4, or the transition metals of period 7? Logically it should mean the latter (as "first-row transition metal" means the period 4 transition metals), yet I have seen both meanings being used. Double sharp (talk) 12:45, 12 July 2014 (UTC)


 * As you indicate yourself, you have seen both meanings used, so you'll have to decide in context. I agree that according to common terminology, it should refer to period 7 elements. However, these elements are all highly unstable and I don't think they've ever been synthesized in significant quantities, so we know almost nothing about their chemical properties. If not in the context of synthetic isotopes or nuclear stability, any discussion of period 7 transition metals would be highly unusual. - Lindert (talk) 13:00, 12 July 2014 (UTC)


 * Indeed: I was also wondering, though, if there is an official definition given by IUPAC. Double sharp (talk) 13:49, 12 July 2014 (UTC)

Conductivity of EMFs through stainless steel water bottles
Hello,

I would like to know whether EMFs and RFs travel through the wall of stainless steel water bottles and into the water within, or whether they actually block the EMFs and RFs from entering the water. Stainless steel is used in insulating against EMFs because it captures the EMFs and stops them from going further ... but there is also a conductive aspect to stainless steel as well, and I am wondering if it would go into the water since the water is in DIRECT CONTACT with the stainless steel. I have been reading about skin depth but it's too technical for me to understand, and I'd appreciate someone answering this question as simply as possible!

Many thanks,

Fiona — Preceding unsigned comment added by 125.168.119.74 (talk) 12:53, 12 July 2014 (UTC)


 * If the water is entirely enclosed by steel (or any other electrical conductor), then there is no electric field in the water, and no electromagnetic waves can penetrate into the water. However, a constant magnetic field is not blocked by the steel, so there can be magnetic forces acting inside the water.
 * (Explanation: The conductive aspect of steel is exactly why it insulates against electric fields. The reason is that electrical conductors contain free electrons. Whenever a field is generated in the conductor, the electrons move in such a way as to counteract the field. That's why a space enclosed by a good conductor can have no electrical fields in it. This also includes the water. Since EM-waves (such as visible light, microwaves, radio waves, UV X-ray etc.) rely on oscillating electric fields that generate oscillating magnetic fields and vice versa, these are also blocked. However, there are no materials that can block stative magnetic fields, and such materials cannot even exist according to current theory (source)) . - Lindert (talk) 13:25, 12 July 2014 (UTC)


 * Just curious as to the reason for this Q. Do you think an EMF will somehow degrade the water ? StuRat (talk) 13:34, 12 July 2014 (UTC)


 * Hi Stu, yes, I was thinking along these lines, that EMFs may impact the integrity of the water somehow. No scientific basis for this line of thought, just an intuitive feeling that I don't want WIFI in my water!


 * Well, in that case, shouldn't you be far more worried about EMFs degrading the much larger quantity of water already in your body ? I don't think the water bottle is much of a risk, at least not due to EMF.  If the container has chemicals in it that can leach into the water, that would be more of a concern. StuRat (talk) 15:34, 12 July 2014 (UTC)


 * (ec) You are headed in the right direction. Skin depth depends of the material and the frequency of the EM radiation.  If the skin depth of a material (stainless steel in this instance) is somewhat less than the thickness, it acts as an effective shield, blocking the radiation.  From the graph in article, steel-410 has a skin depth at 50 Hz (mains frequency in many parts of the world) of about 1.8 mm, and thus a steel wall of say 1 mm would only partially shield an EM field at this frequency, allowing through around 30% of the power.  The higher frequencies of FM radio (88–108 MHz) are over 1 million times higher, and the skin depth will be closer to 0.03 mm, making steel an extremely effective shield at these frequencies.  It will be a very effective shield against EM of frequencies above say 1 kHz, including mobile phone radiation, microwaves, light, etc., up to but not including X-rays. Most steels will be similar in skin depth, and thus the type of steel does not make a real difference when exact figures are not needed. —Quondum 13:48, 12 July 2014 (UTC)

Thank you, wise folk, for explaining this... I UNDERSTAND! So you did your job well! Especially interesting how the higher the frequency, the thinner the skin depth necessary to shield. I can rest now, knowing my drinking water is (on the whole) safe and sound.

Partial condoms
Why do condoms cover the entire shaft of the penis? As far as I know, it's only the head that needs protecting. The shaft can stay unprotected as it is skin and not membrane. I presume it's mainly so that it doesn't slip off but has anyone invented a condom which doesn't slip off and only covers the head? In addition, has anyone invented condoms where you don't need to pull out after ejaculation? — Preceding unsigned comment added by 90.192.101.145 (talk) 15:09, 12 July 2014 (UTC)
 * In my young day (some decades ago now), these were available - we used to call them "American Tips", and a search on this term gives some results, but nothing I'd call reliable. "Short cap condom" or "head condom" is also a term that comes up. There is apparently a new brand on the market called the "Galactic Cap", but I can't vouch for its effectiveness. Tevildo (talk) 15:30, 12 July 2014 (UTC)
 * Nor should you. Promoters of the "Galactic Cap" tout a penis end-covering that is held on with a sticky pad. An evening that ends in fumbling in the dark to recover a rubber scrap lost somewhere near her ostium of uterus (Cervix) can dampen a romantic M-F encounter. If it should slip off the penis, the reinforced aperture of a normal Condom of length about 19 cm helps one to withdraw it from the receiving partner by hand without spillage. The conventional length also lets one knot the used condom with the seminal fluid inside, which is a proper way of disposal. 84.209.89.214 (talk) 20:42, 12 July 2014 (UTC)
 * Some early types of condoms covered only the glans -- but these had to be tied on with string, which was inconvenient. 24.5.122.13 (talk) 23:22, 12 July 2014 (UTC)

Spatial differentiation in the mammalian visual system.
There are two types of signal differentiation in the mammalian visual system: (1) In respect to time which is compensated by the saccadic movements (in humans) and (2) spatial differentiation in respect to retinal, let's say polar coordinates. This differentiation results in sharpening the contours of the images and suppression of the vast areas between the contours. In short the inside of the contour with homogeneous light distribution does not send signals to the visual cortex or perhaps secondary visual areas (18 & 19). My question is about the second type of differentiation. At some stage the brightness/color information is restored to fill the insides of the contours. This information is taken from the homogeneous contours themselves. Does anybody remember the types of experiments that discover this? I think it had something to do with attaching small mirrors to the cornea and thus fixing some test images in a stable position but I do not recall much beyond that, but I need to know it. Thank you. --AboutFace 22 (talk) 15:48, 12 July 2014 (UTC)

"Medical" pot
Have there been any serious proposals to use marijuana as a treatment for tuberculosis? (Note: I don't smoke pot and I don't have TB, so this is not medical advice. Also, I don't support "medical" marijuana in general, and in particular I think that using it for TB would be a stupid idea -- I'd just like to know if other people came up with it.) 24.5.122.13 (talk) 23:20, 12 July 2014 (UTC)


 * What were you smoking when you conceived this seemingly pointless question? —Tamfang (talk) 00:46, 13 July 2014 (UTC)


 * Apparently, hotboxing a car is a good way to spread TB. Doesn't seem to cure it. InedibleHulk (talk) 01:08, 13 July 2014 (UTC)

Extra cost of launching satellites from Scotland
How much extra could it cost to launch satellites from a fairly high-latitude country such as Scotland (mainland about 55° - 58° 38′ N)? I ask because today the BBC reported "Scotland could be base for spaceport, says UK government". Virgin Galactic did talk of launching from Lossiemouth (57° 43′ N) but have switched to New Mexico. NebY (talk) 23:53, 12 July 2014 (UTC)
 * It depends on orbital inclination -- if you're launching into equatorial orbit, it can cost a lot more than from a southern location like Cape Canaveral, but if you're launching into polar or other high-inclination orbit, it could actually cost less (which is why the Russkies launch their polar-orbit Molniya comsats from Plesetsk instead of Baikonur). 24.5.122.13 (talk) 00:43, 13 July 2014 (UTC)
 * There are also safety considerations, which vary according to inclination. One has to consider inhabited areas many hundred miles or kilometers along the flight path, if a launch fails. This is one reason why U.S. space launches heading south into polar orbits take place from Vandenberg in California, heading out over the open eastern Pacific, as opposed to Canaveral in Florida, which would head south over Cuba, the inhabited Carribean, and northeastern parts of South America. Cullen328  Let's discuss it  06:08, 13 July 2014 (UTC)
 * Scotland wouldn't be a great place from which to launch into a low-inclination orbit (it would pass over inhabited Scandinavia, the Baltic states, and northern Russia; dropping space debris on St. Petersburg is not a great way of endearing yourself to the other spacefaring nations), but it would be an excellent polar-orbit launch site, as any debris would head north over open ocean, and wouldn't encounter inhabited land until it had passed over the entire Arctic Ocean. A failed polar launch from Scotland might be bad for the polar bears, but at least the debris would be falling on space uninhabited by humans (and humans are the ones who pay taxes, start lawsuits, and complain if space debris falls on their heads). Whoop whoop pull up Bitching Betty &#124; Averted crashes 16:08, 14 July 2014 (UTC)
 * You also have to consider whether there is a suitable technology base in the country. Are there engineering facilities and companies capable of building the site?  Are there people educated to work there? Is there a hardware shop that can sell all the parts you need to launch a rocket? Graeme Bartlett (talk) 07:32, 13 July 2014 (UTC)
 * I don't know what they are planning. If it is a spacecraft like SpaceShipOne, it can be launched by a carrier airplane taking off horizontally. In this case, the spaceport will look completely different. OsmanRF34 (talk) 19:58, 13 July 2014 (UTC)


 * According to the Sunday Times: “We are looking at sites beside the sea, without crowded airspace but with a long runway, said Willetts, who recently visited the California base of Virgin Galactic, Sir Richard Branson’s company, which hopes to offer space flights for tourists and to launch small satellites...Our ambition is to have a fully operational spaceport in the UK by 2018. Virgin told me they would be keen on coming here but they are not the only candidates” They go on to say:  "The choice of site will be difficult. Scotland offers some technical advantages because northerly sites are better for putting satellites into low Earth and polar orbits, but places such as Cornwall and south Wales have excellent communication links". And "In the longer term, the spaceport could become home to supersonic spaceplanes such as the Skylon".  Richerman    (talk) 17:33, 14 July 2014 (UTC)


 * "WHOOP WHOOP PULL UP" I would rather protect the polar bears. --AboutFace 22 (talk) 23:49, 14 July 2014 (UTC)
 * I bet the European Space Agency would want to have a word or two in that and most likely these two would be: "No way!" --Kharon (talk) 01:54, 15 July 2014 (UTC)


 * I don't know, but I have this feeling that if you're doing space tourism your VIPs don't want to be cooling their heels around some tropical island for days waiting for weather and technical issues to permit a launch. And what's the point of piling up millions of pounds and setting them on fire if you don't do it where a lot of (less) important people will see it?  I wonder if them hearing it is also a criterion ... if they can't arrange for the rockets don't make a sonic boom over London, would it be taken as a sign of weakness? Wnt (talk) 18:54, 15 July 2014 (UTC)