Wikipedia:Reference desk/Archives/Science/2019 November 28

= November 28 =

Nostrils
Why do human nostrils have their opening pointing down compared with chimps, and other mammals who have them sticking out  normal to the plane of their face.,? Ie forward. 86.8.202.181 (talk) 00:29, 28 November 2019 (UTC)
 * This article discusses the question. ←Baseball Bugs What's up, Doc? carrots→ 01:12, 28 November 2019 (UTC)


 * As does the following:
 * ...which references the following journal article:
 * —2606:A000:1126:28D:9417:2118:29F3:6E25 (talk) 01:31, 28 November 2019 (UTC)
 * I must admit I find the explanations rather unsatisfactory. If it is so much less efficient evolution would have acted against it, after all they're saying evolution has changed it going from warmer to colder climates. It would ha eto be somethng reasonably important like aiding swimming or persistence hunting or countering disease. Something a bit better than what thy say I'd have thought. Dmcq (talk) 12:19, 29 November 2019 (UTC)
 * —2606:A000:1126:28D:9417:2118:29F3:6E25 (talk) 01:31, 28 November 2019 (UTC)
 * I must admit I find the explanations rather unsatisfactory. If it is so much less efficient evolution would have acted against it, after all they're saying evolution has changed it going from warmer to colder climates. It would ha eto be somethng reasonably important like aiding swimming or persistence hunting or countering disease. Something a bit better than what thy say I'd have thought. Dmcq (talk) 12:19, 29 November 2019 (UTC)


 * The swimming nose idea is used as evidence by supporters of the discredited aquatic ape hypothesis (but it still sounds reasonable to me!). Alansplodge (talk) 22:07, 1 December 2019 (UTC)

Who is a climate scientist?
where I can find definition? — Preceding unsigned comment added by 61.68.141.189 (talk) 02:46, 28 November 2019 (UTC)
 * You could start by reviewing List of climate scientists. ←Baseball Bugs What's up, Doc? carrots→ 03:19, 28 November 2019 (UTC)


 * See also: Climatology (a scientist who studies climate is a climatologist; also related: paleoclimatology) —2606:A000:1126:28D:9417:2118:29F3:6E25 (talk) 03:57, 28 November 2019 (UTC)


 * Since underwater military (Submarines) became a very important focus in the last century and science was very surprised by the huge impact of earthe's Oceanography on it's atmosphere, very specialized sciences like Bathymetry have become a thing you can actually study and make your profession. --Kharon (talk) 03:52, 29 November 2019 (UTC)

Cybertron is the size of Saturn
In the Transformers comics, Cybertron is said to be the size of Saturn. Cybertron is obviously a solid planet, consisting almost entirely of rock and metal, not a gas planet like Saturn. Now ignoring the fiction that it's all populated by sentient living robots, could a rocky planet of such a size exist in the first place? J I P &#124; Talk 11:07, 28 November 2019 (UTC)
 * This is all very hypothetical. What's the biggest planet which could form? Would it be rocky? What happens if it's bigger?
 * Kevin C. Schlaufman has written on this https://iopscience.iop.org/article/10.3847/1538-4357/aa961c
 * His work is mostly based on observation (we see evidence for things up to the mass of 10 Jupiters, but not bigger). We do see bigger things, but they mostly become luminous as stars.
 * In our limited Solar experience, larger planets have been formed as gas giants: once they had a large rocky core, they then accreted lighter elements and so their main volume remains gaseous. But could a large rock have accreted, if the materials were there?
 * Schlaufman's paper takes the accepted view that large bodies form either by core accretion (as planets do), or by gravitational instability (as stars do). But these both form objects in a range of masses, and those mass ranges don't overlap. So "planets" aren't found with more than 10 Jupiter masses (which would be a problem for something as dense as a rocky planet that diameter). Andy Dingley (talk) 12:56, 28 November 2019 (UTC)
 * List of transiting exoplanets has several planets with estimated densities that are larger than Earth's, including planets of several Jupiter masses. This high density is presumably not sufficient to characterise them as rocky planets, though. --Wrongfilter (talk) 13:29, 28 November 2019 (UTC)
 * We can set an upper limit by assuming that somebody would have noticed it if Cybertron was a Neutron star or a Black hole... --Guy Macon (talk) 17:03, 28 November 2019 (UTC)


 * According to our article Hot Jupiter the biggest planetary mass cannot be greater than approximately 13.6 Jupiter masses, because then the planet would start burning deuterium and become a brown dwarf aka a star. However the search for exoplanets is still a very young science field and we know there are "gazillion popillion" of stellar objects out there waiting to be found. --Kharon (talk) 03:19, 29 November 2019 (UTC)
 * Though if it was made of rock, deuterium would be low level, and thus it may not be a brown dwarf. The problem may be to get a lot of rock together without getting too much gas, otherwise you would get something like Neptune. Graeme Bartlett (talk) 03:32, 29 November 2019 (UTC)
 * If you're big enough, you become a vacuum cleaner for the light elements too, and thus you not only accrete rock, but you acquire the gaseous layers of Jupiter or Saturn. Do it on a big enough scale, and you also get the deuterium and tend towards starhood. It's not simply that "you might or might not acquire fusible materials", it's that if you're big enough, you will. Schlaufman also ties this to the mechanism by which the body forms. Andy Dingley (talk) 16:28, 29 November 2019 (UTC)

Let's go back to the beginning assumption. The question at the top of this thread says
 * "Cybertron is obviously a solid planet, consisting almost entirely of rock and metal"

but our article on Cybertron says
 * "Cybertron is described in the first issue of the Marvel comic book as being the size of Saturn, which would logically mean it possessed incredibly dense gravity, and yet it did not, possibly as a result of its hollow structure, honeycombed as it is by tunnels. However, in later depictions the art suggests Cybertron is much smaller..."

So that answers the question for Cybertron. But the more general question of very large planets is still interesting. Assuming a large planet made of the same stuff as a Stony-iron meteorite, and assuming that it is far enough way from the star to not be torn apart by tidal forces, is there an upper limit to size other than the neutron star and black hole limits? --Guy Macon (talk) 05:39, 29 November 2019 (UTC)