Wikipedia:Reference desk/Archives/Science/2020 July 10

= July 10 =

Lack of sleep and blood vessels
Does severe sleep loss damage blood vessels in the brain or spine?Rich (talk) 05:46, 10 July 2020 (UTC)
 * I do not think that it damages vessels at least directly. Ruslik_ Zero 06:42, 10 July 2020 (UTC)
 * Any personal knowledge, or reasoning, or references for your opinion? I don’t know you, so of course I can’t just take your word for it. Also, if it did cause it, “indirectly” it would still be of moment.Rich (talk) 09:00, 10 July 2020 (UTC)
 * Not directly, but, changes in circadian rhythms can have a trigger effect for scotoma. Which is caused by a blood vessel in the optical cortex at the back of the brain not dilating properly.86.172.130.137 (talk) 08:41, 10 July 2020 (UTC)
 * Thanks..well does loss of sleep affect the blood-brain barrier, or impede its development in infants?Rich (talk) 09:03, 10 July 2020 (UTC)
 * "Sleep Restriction Impairs Blood–Brain Barrier Function" - J Neurosci. 2014 Oct 29; 34(44): 14697–14706. Fgf10 (talk) 09:25, 10 July 2020 (UTC)


 * This is one of those questions where my answer is "see a doctor, and do is soon." There are a huge number of ailments that interfere with sleep, and some of them are quite nasty if not treated. Seriously. Take care of yourself. Wikipedia is not a Doctor. --Guy Macon (talk) 17:57, 10 July 2020 (UTC)
 * Ok, but to be clear, I'm not asking for medical advice, I'm just curious.144.35.45.25 (talk) 00:29, 14 July 2020 (UTC)

Covid-how it affects bats vs how it affects humans
Ill try not to be a bore, but i'm going somewhere with this: There is avian and swine flu. Possibly, if there is enough time, in either type of flu the different strains have evolved to do well in the particular specialized circumstances of a bird or a pig, and the environment of each. So then whatever is the best way for a virus to cause a pig to transmit the virus to other pigs would selected for, and similarly, however a virus could best survive the pig's immune system would be selected for. The same goes for bird flu in birds. So, when bird or swine flu infect humans, does their effects on human bodies roughly analogous to what their effect on birds or pigs is, given that all 3 species, bird, pig, and human are at least somewhat related?..If so, to change the subject and get to the point, what about coronavirus from bats- could we understand the symptoms in humans by studying the nature of the Wuhan bat and it's environment? What would a virus try to make a bat do to spread the virus to another bat? Granted our bodies and brains are quite different from bats bodies and bains, we are related species, so if there is some pathway in a bat that the virus exploits to spread the virus or survive the bat’s immune system, there are probably at least some analogous pathways in humans that the virus would tend to affect? Ive heard coronavirus causes puzzling symptoms in humans, maybe we could understand them that way? As a further question, are the scientists who study coronavirus able to infect lab mice with it? If so, how does coronavirus affect mice?24.11.81.123 (talk) 08:29, 10 July 2020 (UTC)
 * The most favourable evolutionary outcomes for a virus is to effect its (usual) host adversely as little as possible while remaining as infectious as possible. Possibly because of their unusual (for mammals) metabolism, bats are routinely infected with many different coronaviruses that appear to have little detectable effect on their health: it's the rare-ish occasions when one of those viruses infects some other creature, and mutates so as to be infectious in that new species (and onward to yet other species) it is less well adapted to, that the troubles start. The virus's effects on its novel host(s) may be very, and unpredictably, different.
 * Consider that humans are already routinely infected by 4 other different coronaviruses which together cause about a quarter of cases of the (trivial) Common cold. Those particular coronaviruses may themselves have caused pandemics (which at the time may have gone unnoticed amongst all the other disease-caused deaths) when they first infected humans anywhere between 100 and 10,000 or so years ago, but natural selection has resulted in them becoming relatively innocuous: of course, they will have killed a lot of people during that process.
 * I'm not at the forefront of the massive international scientific study of SARS-CoV-2, so I'll leave others to address your further points. {The poster formerly known as 87.81.230.195} 2.122.58.253 (talk) 17:50, 10 July 2020 (UTC)

Static Electricity Units
Is the SI unit for static electricity joules? Static electricity can completely convert into energy (joules) via discharge.


 * $$ Energy Stored = \frac {CV^2} {2} $$

Volts can be a property of static electricity and capacitance is a property of a container for static electricity. Vze2wgsm1 (talk) 12:02, 10 July 2020 (UTC)
 * The SI unit of electrical charge is the Coulomb Q = C × V. Joules weights for energy. The two probably might be considered equivalent, though not necessarily up to the extreme limit of all possible patterns for a discharge (the uncertainty principle). --Askedonty (talk) 12:47, 10 July 2020 (UTC)
 * The things that make static electricity unique, such as charge or the ability to accelerate an electron can belong in the definition of static electricity. The complete convertibility of static electricity into joules is all that is necessary for assigning joules as a unit for static electricity.  Vze2wgsm1 (talk) 14:38, 10 July 2020 (UTC)


 * What precisely are you asking about? Static electricity is a set of different, although related, physical phenomena, hence it has no unit. Different quantities appearing in those phenomena have different units.
 * A unit for an electric charge is coulomb.
 * A unit for an electric potential is volt, hence same unit is for voltage, which is a difference in electric potentials.
 * A unit for electric potential energy is joule, the same as for other kinds of energy.
 * The electric field's unit is volt per meter while the electric flux has a unit volt × meter.
 * CiaPan (talk) 14:25, 10 July 2020 (UTC)


 * static electricity = work does not have a units problem, because a capacitor’s static electricity completely converts into work. If properly calculated, the work of converting a charge imbalance that creates static electricity into balance without static electricity does not create a units problem.  Vze2wgsm1 (talk) 15:12, 10 July 2020 (UTC)
 * Not necessarily. There is no ideal object in the real world. There is also no ideal circuit. Depending on parameters of the circuit you use to discharge the capacity, some part of the potential energy accumulated in the electric field will be converted into useful work, some will dissipate in heat and electromagnetic radiation. Anyway, the work and the energy have the same unit of course. --CiaPan (talk) 15:59, 10 July 2020 (UTC)
 * Because of the conservation of energy law, anything that is not energy cannot convert to or from static electricity. Vze2wgsm1 (talk) 05:31, 15 July 2020 (UTC)

Where is it possible to compare between the hair and nail growth of 6-7-8 month premature baby?
Where is it possible to (see photos) and compare between the hair and nail growth of 6-7-8 month premature baby (preterm)? I want to see the differences immediately after the birth of each of them? Of course, I expect them to be more developed with age, but I want to see and examine the differences.--ThePupil (talk) 14:50, 10 July 2020 (UTC)
 * In medical school? — Preceding unsigned comment added by 86.172.130.137 (talk) 16:07, 10 July 2020 (UTC)

Is there a name for the opposite of a Sun-synchronous orbit
Is there a name for an orbit which would keep a satellite in the shade of the Earth, without ever getting light from the sun. This would be useful for keeping a satellite away from the danger of massive, irregular solar flares and the regular radiation from the sun.--AlainV (talk) 20:21, 10 July 2020 (UTC)
 * This sounds like L2. But the orbit is unstable, and it's far enough from the Earth that I'm not sure you could really count on being in the "shade" all the time. --Trovatore (talk) 20:25, 10 July 2020 (UTC)
 * It would never be. The Sun's diameter is about 109 times the Earth's, but the Sun is only 100 times (almost exactly) as far from the L2 point as the Earth is. So from that position the Earth isn't large enough to block the entire Sun from view. --174.89.49.204 (talk) 20:49, 10 July 2020 (UTC)
 * Nicely explained. In fact Lagrangian point mentions this fact: It is, however, slightly beyond the reach of Earth's umbra, so solar radiation is not completely blocked at L2.  But it doesn't give your very succinct and clear reasoning. --Trovatore (talk)
 * Also, you can't actually sit at L2 without active thrusting anyway, see Lissajous orbit. In practice you're always some distance away. This very fact has been utilised by Chang'e 4 relay satellite Queqiao in the Earth-Moon L2 point, as it always has line of sight of Earth. Replace Earth with the Sun and the Moon with Earth and you can see they satellite will always see the sun. Fgf10 (talk) 09:54, 11 July 2020 (UTC)
 * Unless I'm missing something, wouldn't that simply be a midnight orbit (essentially a SSO -180°). 2606:A000:1126:28D:20AC:E64A:14AD:A6E4 (talk) 20:56, 10 July 2020 (UTC)
 * Doesn't a SSO with a midnight pass imply a noon pass half an orbit later? -- 196.247.57.148 (talk) 21:33, 10 July 2020 (UTC)
 * The article is difficult for this lay-person to digest -- I believe it means that it is synchronized such that the satellite maintains orientation with respect to the sun (but I may be wrong). I.e.: "...it always maintains the same relationship with the Sun." -and- "...it is possible to always point the instruments towards the night side of the Earth."  2606:A000:1126:28D:20AC:E64A:14AD:A6E4 (talk) 21:47, 10 July 2020 (UTC)
 * Yes, it would imply a noon pass half an orbit later, on the other side of the world. An SSO simply means the satellite passes any given location of the earth surface at the same local solar time. If you use a terminator orbit (the link is for Venus, but just as possible on Earth), yes you could always point your instruments at the night side (off nadir). But your spacecraft will in fact always be in sunlight. Fgf10 (talk) 09:54, 11 July 2020 (UTC)
 * A satellite in GEO (geosynchronous equatorial orbit 35,786 kilometres (22,236 miles) above Earth's equator remains fixed above a given longitude if it follows the direction of Earth's rotation. If however it orbits in the opposite direction it can remain above the night portion of the equator (though it approaches existing communications satellites twice daily and collisions with them may cause complaints). — Preceding unsigned comment added by 84.209.119.241 (talk) 22:44, 10 July 2020 (UTC)
 * Nice try; had me going for a minute. But no.  Such a satellite still orbits the center of the Earth, in a non-rotating frame of reference, once every 24 hours.  It will spend roughly half its time on the "day" side of the Earth.  (I say "roughly" because the Earth is moving in its orbit, changing the plane of the terminator, and there are other complications like the Earth's eccentricity that I don't want to think about too hard.) --Trovatore (talk) 23:15, 10 July 2020 (UTC)
 * At GEO orbit (for the normal prograde orbit), night is far far shorter than half the orbit, because of the altitude and the axial tilt of the earth. Night only happens when the Earth eclipses the sun, which for their orbit is only around the equinoxes. Fgf10 (talk) 09:59, 11 July 2020 (UTC)
 * A statite could maybe theoretically do it, were it not that most concepts rely on solar pressure. Bascially to remain on the dark side of the planet requires constant thrusting. I cannot be done with a basic Keplerian orbit. Fgf10 (talk) 09:54, 11 July 2020 (UTC)

If the opposite of a sun-synchronous orbit cannot be done around the Earth, can it be done around the Moon?--AlainV (talk) 05:42, 12 July 2020 (UTC)
 * Orbits work the same for all bodies (notwithstanding oddities like close binaries), so no. Fgf10 (talk) 09:41, 12 July 2020 (UTC)
 * Thank you!--AlainV (talk) 10:14, 12 July 2020 (UTC)