Wikipedia:Reference desk/Archives/Science/2018 May 7

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May 7

Harbor Seal colors

I was observing Harbor Seals today and wondering, why are they so varied in color? They range from white with black spots to blackish gray with white spots, and occasionally a sandy-brown tone, with varying spots. Also, do they prefer to mate with seals of the same color, and if not, how is the color of their young genetically determined? 169.228.164.251 (talk) 01:15, 7 May 2018 (UTC)

Asking "why" in evolution is fraught, since it tends to invite a just-so story by way of response. I'll admit, I have no idea -- many species e.g. dogs and horses have a vast repertoire of colors when bred in captivity, but use much less of it in a truly wild population. Some of the same genes are likely to be involved, but that wouldn't touch on why. Does it help them to be recognized as individuals at a distance in water? Is it balancing selection between different color options that might find safe refuge against predators in different environments? I have no idea, but my gut feeling is that if you see a wide variety of stuff, there ought to be balancing selection acting on something (not necessarily that). Wnt (talk) 02:11, 7 May 2018 (UTC)

Color morphs, as they are known, are very common in natural populations. In addition to the apostatic selection selection for not looking like what the predator expects as User:Wnt mentioned, there's sexual selection and various types of frequency-dependent selection. For an example, picture a scenario in which black panthers are locally common. Perhaps females will mate with the rarer spotted males until they are more common, then switch back to the black ones. Similarly, females may be reluctant to mate with a male who has the same blotches of color as she can see on her own body, as a method of incest avoidance. Abductive (reasoning) 03:30, 7 May 2018 (UTC)

I'm not sure if this counts as polyphenism since I don't know if there's a list of specific color options in response to environment or just a lot of continuous variation. (The other option is genetic polymorphism). Wnt (talk) 10:23, 7 May 2018 (UTC)

Equine coat color genetics are so complex, they have their own article. Carbon Caryatid (talk) 20:10, 8 May 2018 (UTC)

Oooops. That article starts off with a predicted range of wild horse colors pre-domestication that is much larger than I thought it was, and perhaps well analogous to the seals. Wnt (talk) 23:02, 9 May 2018 (UTC)

Prostate and pancreas

How many millimeters are the prostate and pancreas from each other in the human body? Do they ever come into contact and push each other? Thanks107.77.230.130 (talk) 07:53, 7 May 2018 (UTC)

Exact distance will depend on your size, but the pancreas is just under the liver, so will never come into contact with the prostate unless something is very wrong. Fgf10 (talk) 07:59, 7 May 2018 (UTC)

See this diagram. The prostrate is not shown but it sits just underneath the bladder. Alansplodge (talk) 15:17, 7 May 2018 (UTC)

D'oh! Should have been "prostate" and not "prostrate" as I well know, but apparently my fingers don't. Thanks to DroneB for spotting this. Alansplodge (talk) 19:35, 7 May 2018 (UTC)

Our prostate article has what I think is a fine illustration. As for the questioner, if your pancreas and prostate are anywhere close to making contact, you'll either be dead or in surgery. Are you sure you're not confusing one of these with a different organ? --47.146.63.87 (talk) 05:32, 8 May 2018 (UTC)

Space launch

At the Baikonur Cosmodrome, about how long does it take to prepare a rocket for launch (from payload mating to liftoff)? 2601:646:8E01:7E0B:545A:B8DD:210:5A3E (talk) 11:10, 7 May 2018 (UTC)

It depends on type of rocket. Ruslik_Zero 20:37, 7 May 2018 (UTC)

Let's say the most common type of all. 2601:646:8E01:7E0B:FDA1:AEB9:3ACB:8095 (talk) 09:49, 8 May 2018 (UTC)

I don't know if this helps, but section 7-18 of the Soyuz user manual says "The spacecraft campaign duration, from equipment arrival in French Guiana until, and including, departure from Guiana, shall not exceed 32 calendar days (29 days before launch and day of launch, and three days after launch)." which I take to mean about 3 weeks or so to prepare a launch. Elsewhere it says "Soyuz LVs are produced in Samara, Russia, by the Samara Space Center, whose facilities have been designed to accommodate the production of up to four LVs per month." which is quicker than a Bugatti Veyron and they'll tell you rocket science is difficult :) --TrogWoolley (talk) 14:55, 8 May 2018 (UTC)

JUst as a point of order, the rocket science comes in the design of the thing. The Soyuz is the world's most common spacecraft, and the assembly of them has become routine. At this point its just a manufacturing and quality control operation. The actual science is past. --Jayron32 15:00, 8 May 2018 (UTC)

Well, this doesn't help -- the first part deals with the maximum timeframe for the launch, whereas I'm looking for the minimum time required, and the second part deals with the production of the rockets which has nothing to do with the launch. (Also, the first part talks about the time from equipment arrival, whereas I was asking specifically about the time from payload mating to LV -- and also it deals with launch from French Guiana, which probably has a much longer launch time than Baikonur because of the need to ship everything halfway around the world.)2601:646:8E01:7E0B:FDA1:AEB9:3ACB:8095 (talk) 01:48, 9 May 2018 (UTC)

To give another data point, according to this NASA blog Soyuz MS-08 was encapsulated in its launch shroud on 14 March, which happens before mating to the booster, rolled out to the launch site on 19 March and launched on 21 March. PiusImpavidus (talk) 09:04, 9 May 2018 (UTC)

Now THAT was useful info! So, 5 days from encapsulation to rollout (although this may have been longer than the minimum needed due to scheduling issues), 2 days from rollout to launch (I presume most of this time is used to (1) move the rocket to the pad, (2) lift it upright, and (3) fuel it up), and once fueling is complete it takes about 3 hours to prepare for launch -- right? (As an aside, this is why the R-7 would never have worked as an intercontinental missile -- from the moment Khruschev gave the order to nuke Washington, it would have taken 2 days to prepare the missile for launch, and for all of that time it would have been out in the open where just one stray B-52 could easily blow it to bits!) 2601:646:8E01:7E0B:FDA1:AEB9:3ACB:8095 (talk) 01:42, 10 May 2018 (UTC)