Wikipedia:Reference desk/Archives/Science/2016 March 5

= March 5 =

Do all mammals have pair of kidneys like human being has?
(I know for example about the prevailing opinion which claims that all mammals have 7 cervical vertebra, but in fact it's not true and there are at least 3 mammals which don't have 7 cervical vertebra. That's why I'm asking here about the kidneys to see if there is an exception like in the issue of the cervical vertebra) 93.126.95.68 (talk) 01:01, 5 March 2016 (UTC)


 * I don't know for sure, but bilateral symmetry would seem to mean an organism would typically have an even number, unless they are located on the sagittal plane. StuRat (talk) 01:17, 5 March 2016 (UTC)


 * Some humans have one kidney, an extra large horseshoe shaped kidney across the back. Graeme Bartlett (talk) 01:32, 5 March 2016 (UTC)


 * And some have three! DuncanHill (talk) 01:35, 5 March 2016 (UTC)


 * Does the OP mean "Do all mammals normally' have a pair of kidneys? DrChrissy (talk) 01:43, 5 March 2016 (UTC)
 * That's right. My question is about the normal cases rather than about abnormals.93.126.95.68 (talk) 02:33, 5 March 2016 (UTC)


 * In Mammals, and many other Vertebrates there is also the Mesonephros, which for humans is around from the sixth to tenth week of the gestation. A Pronephros also forms in mammals, but since it is non-functional as a kidney, I don't think you can call it that. So you may wish to confine you scope to adults. Graeme Bartlett (talk) 03:57, 5 March 2016 (UTC)
 * That's technically true but bordering on the needlessly pedantic. (You could say that not all humans have any kidneys because a 3-day-old embryo only has 8 undifferentiated cells.  Or that not all mammals have a four-chambered heart because a 3-week-old human embryo just has a primitive heart tube.) TenOfAllTrades(talk) 19:55, 7 March 2016 (UTC)

Falcon 9 full thrust
I was photographing the launch of the Falcon 9 full thrust today and a while after it dropped the first stage, it dropped something else. Does it drop the payload shroud while the second stage is still burning? Bubba73 You talkin' to me? 03:24, 5 March 2016 (UTC)


 * Yes, it jettisons the payload fairings early in the second stage flight. The timeline from spaceflightnow gives:
 * T+0:02:47: First Ignition of Second Stage
 * T+0:03:42: Fairing Jettison
 * which is just under a minute into the second stage burn. I too saw what I now assume were the fairings, but I didn't realize what they were until you asked.  I hope you got some good shots. I tried a long duration exposure (from a long distance away), but it didn't come out that well.  I think the later (1846 vs 1835) launch time they had planned last week (as well as the slightly earlier sunset then) would have helped me, but I see that some people (a lot closer to the Cape) got some very good shots despite the light.  -- ToE 05:01, 5 March 2016 (UTC)


 * I'm 180 miles from the cape, and longer after the rocket gets up a bit. The launch was 8 minutes after sunset so I knew that the sky would be too bright for a time exposure (which I often do).  I got several shots after the first stage was dropped, showing both, but then I was looking at the photos, and at least one showed something else being dropped off, well after the first stage.  It must be the fairing.  And also there are two small points (1 pixel each) near the fairing that might be some sort of associated debris.  Bubba73 You talkin' to me? 07:52, 5 March 2016 (UTC)
 * Does this rocket use explosive bolts to jettison the fairing? That might be your 2 pixels.  --DHeyward (talk) 10:48, 8 March 2016 (UTC)

I added a photo. You can see the two parts of the fairing, plus the first stage. Bubba73 You talkin' to me? 21:00, 5 March 2016 (UTC)


 * Nice. Here is some amateur video shot from Wilmington, NC (400 mi to the north) starting at second stage ignition, running through fairing separation, and showing plumes from the second stage at the start and end of its reentry burn. -- ToE 13:43, 7 March 2016 (UTC)

"chemical castration" for racehorses
My earlier question about (not) castrating a cat got me thinking: Male racehorses are pretty routinely gelded in the hope of improving their performance on the racecourse. The very obvious disadvantage is that they are rendered permanently infertile, and if they turn out to be a star winner, you can't breed with them.

Wouldn't an equine form of Chemical castration (administering androgen-suppressing drugs) be a possible alternative in terms of getting the horse to perform on the racecourse as if it was a gelding, whilst still being able to be used as a stud horse once its' racing career was over? (Obviously, at that point, you would simply stop administering the androgen-suppressing drugs, and the horse's sex drive and sperm production would in time return, wouldn't it?). If it was that simple, surely someone would have thought of this idea? Or is it actually being done? Are there veterinary medical difficulties in "chemically castrating" a horse? Cost issues? Or is there some rule of racing in most or all jurisdictions which forbids such treatments being administered to racehorses, even if they would give the horse no competitive advantage over the standard "surgical gelding"? What am I missing? Eliyohub (talk) 11:53, 5 March 2016 (UTC)
 * See Equine drug testing. I don't know if these drugs would actually work, but if they did they would almost definitely fall in the category of performaance modifying drugs. Nil Einne (talk) 16:34, 5 March 2016 (UTC)
 * BTW a simple search for 'racehorse chemical castration' finds Nil Einne (talk) 16:38, 5 March 2016 (UTC)
 * Also, , (while it doesn't mention what was discussed, consider what the meeting was for),  (not about race horses but your question seemed to also be about the general idea of equine chemical castration). Note that not all of these refer to reversible chemical castration, quite a few refer to immunuchemical castration that may not be reversable. However there's no suggestion that will affect the legality of such techniques in racehorses. Nil Einne (talk) 16:46, 5 March 2016 (UTC)
 * I have a related question. Why does castration improve the speed of racehorses?  What is the reason why geldings are faster than stallions?  I hadn't known that geldings were faster until this discussion.  I had thought that horses were gelded to make them easier to handle, not faster.  Robert McClenon (talk) 17:27, 5 March 2016 (UTC)
 * To be honest, I'm not sure it does directly. Most sources I saw when researching this seem to agree it's mostly about handling but also perhaps longevity. See also, , Gelding (see the paragraph that starts with In horse racing and two paragraphs down), , , (although this claims as a rule of thumb for an older horse it may make it race as if it were one year older). In fact the discussion about muscle mass or musculature wonders if it may reduce performance of younger horses. However if you are having trouble training the horse or if it gets distraced during races or whatever, it may effectively help performance (a few of the sources suggest that). Nil Einne (talk) 18:33, 5 March 2016 (UTC)
 * If they are anything like people, the timing can affect all sorts of features including limb length and lung capacity. See Castrati which was done to preserve pre-pubescent voice range.  The effects weren't at all intuitive (at least to me).--DHeyward (talk) 10:38, 8 March 2016 (UTC)

Subject of image File:Jj6.png
While clearing out shadowed files, I have come across this image. I cannot find out what glacier it is of. Does someone here know? Jo-Jo Eumerus (talk, contributions) 16:41, 5 March 2016 (UTC)




 * That photo looks a lot like THIS image of the Mendenhall Glacier in Alaska. That photo shows an expanse of open water at the foot of the glacier (where the people are standing in Jj6.png) - but the photo at right here (which is from our Mendenhall Glacier article) shows the lake freezes and is snowed over in winter. SteveBaker (talk) 18:00, 5 March 2016 (UTC)


 * I added the unknown glacier for comparison. I agree that this looks like the same glacier, but photographed from a slightly different location.  Specifically, the location from which the unknown photo was taken may be more to the right and farther out. StuRat (talk) 19:29, 5 March 2016 (UTC)


 * Yeah, a comparison of the geographical features on the photographies clinches it for me - file moved to File:Mendenhall Glacier.png.Jo-Jo Eumerus (talk, contributions) 19:40, 5 March 2016 (UTC)


 * I updated the pic here accordingly, and will mark this Q resolved. StuRat (talk) 22:15, 5 March 2016 (UTC)

List of possible things that could be gained from the Sun
Apostle (talk) 20:46, 5 March 2016 (UTC)
 * Carbon/emission footprint-less:
 * Free energy:


 * Most forms of energy we use ultimately come from the Sun. Solar, of course, and wind due to uneven heating of the atmosphere by the Sun, and wave energy from the wind, and hydro from precipitation caused by evaporation of water in the sunlight.  Photosynthesis changes sunlight into plant and then animal energy, including all our food, and any wood we burn.  Long ago many of those plants and animals died and produced all the fossil fuels.  Tidal and geothermal energy are partially from the Sun, with the Moon and radioactive decay playing larger roles.  Nuclear energy isn't from the Sun at all.


 * In space, a solar sail can also make use of the Sun to accelerate.


 * The gravity of the Sun moves the Earth in it's orbit far enough so that 6 months apart we can take measurements to the nearest stars and determine their distance by parallax. StuRat (talk) 01:30, 6 March 2016 (UTC)


 * See free energy. It will note that free energy may be either thermodynamic free energy, which is probably not what is meant here, or perpetual motion in pseudoscience.  Obviously the bullet really means economically free, but, as noted above, there is a cost in collecting or harnessing the energy from the Sun.  The only form of usable energy that does not come from the Sun either in the present or in the past is nuclear power.  Uranium is a primordial radioactive element that comes from a star that no longer exists, from supernova nucleosynthesis.  One theory is that the expanding shell from a supernova was one of the causes of the collapse of the protostellar cloud into a main-sequence star with planets.  Robert McClenon (talk) 01:41, 6 March 2016 (UTC)

I'll read through. Thanks. -- Apostle (talk) 18:46, 6 March 2016 (UTC)