Wikipedia:Reference desk/Archives/Science/2020 August 2

= August 2 =

Planet with Earth’s size, made entirely of radium.
Is such a planet theoretically ppssible, or would its gravity be too weak to hold it together, given how much energy it would generate?Rich (talk) 04:36, 2 August 2020 (UTC)
 * What element or elements does radium decay into? ←Baseball Bugs What's up, Doc? carrots→ 04:47, 2 August 2020 (UTC)
 * It can decay in more than one way depending on the isotope, but as far as I know, its end state is lead, although it’s frequently radon for awhile. Rich (talk) 05:09, 2 August 2020 (UTC)
 * The point being, if you started with pure radium, it wouldn't stay pure very long. ←Baseball Bugs What's up, Doc? carrots→ 06:23, 2 August 2020 (UTC)


 * Sorry, but that is definitely not the point. For one thing, an important way to do thought experiments is to consider various extreme cases, such as extreme initial conditions, along with looking at less extreme initial conditions, to get a view of the cone of possible outcomes.Rich (talk) 21:38, 5 August 2020 (UTC)
 * A body in space can generate a huge amount of energy without overcoming gravity and flying apart. Example: the Sun. I suspect that such a planet would fairly quickly become a ball of glowing gas. Even if you pick areally low energy output per atom, most of that energy has nowhere to go. --Guy Macon (talk) 06:38, 2 August 2020 (UTC)


 * You might be right in some ways, but the sun is much more massive than a planet of earth’s size, giving more gravity, and almost all of the hydrogen nuclei in the sun can’t be expected to undergo fusion(thereby giving off energy), in the next few million years. The opposite is the case for the radioactive decay of the atoms of a pure radium planet, due to the short halflife. A lot of energy in a short time could make a big difference.Rich (talk) 21:46, 5 August 2020 (UTC)
 * Where would the radium planet come from? The half life of the longest lived isotope of radium is 1600 years (all the radium in nature comes from processes like uranium decay) and planets are generally believed to accrete from dust over megayear periods.  If you somehow created a planet-sized sphere of radium in an instant, are you asking if the pressure at the center would be enough to cause a giant nuclear explosion?  Hmm, interesting.  I don't see anything in the radium warticle about radium being fissile but I don't know if that means it isn't.  The ordinary radioactive decay would give off a huge amount of heat, let's see.  If my math is right, the mass would be around 6e24 kg, comparable to the mass of Earth.  So from the atomic mass and half life, you can figure out the decays/sec.  The decay is alpha particles but oddly, the energy of the particles is not specified.  I think that's a standard thing: maybe a CRC Handbook would have it?  That would let you figure out the decay heat, and from that I guess the blackbody temperature using the Stefan-Boltzmann law.  It's late now but I may try to figure out the numbers in the next few days.  I'd appreciate if someone who knows more physics than I do could tell me if this method makes any sense.  2601:648:8202:96B0:0:0:0:5B74 (talk) 07:31, 2 August 2020 (UTC)
 * Regarding the as to where you would get such a Radium planet given how slowly planets form, it is on Shelf 42B, right next to the spherical cows. Make sure that you approach Shelf 42B from the left; 42D contains the infinite planes and it takes literally forever to walk past the end of one of those.
 * That calculation seems like the right way to do it. The result will be slightly off because the surface of the radium planet would lose energy from the usual radium glow and from infrared as it became hotter an hotter, but I would be very surprised if those two together reached even 0.001% of the total energy. Eventually the radium would melt and then boil. That could change things a bit; is Radium gas (plus by that time it would have some Radon gas mixed in) transparent to the wavelength where Radium shines? And the surface area would get a lot bigger. I still think it would be a fraction of a percent compared to the total energy output. An interesting calculation would be the time. Does it take a millisecond to heat up to a gas ball or does it take a thousand years? --Guy Macon (talk) 11:18, 2 August 2020 (UTC)


 * Alpha particle says: "Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV, and a velocity in the vicinity of 5% the speed of light." That can be used as a ballpark figure. A much more critical issue is the isotopic composition; I expect the results for pure 226Ra and pure 224Ra to be rather different. This source gives 4.6 MeV for 226Ra decay, while this source gives an alpha energy of 5.69 MeV plus gamma emission at 241.0 keV for 224Ra decay. But in terms of power (energy output per unit of time) the latter is orders of magnitude more powerful. --Lambiam 12:40, 2 August 2020 (UTC)
 * Hmm, thanks, yes I was assuming pure 226 since 224 has a much shorter half life. Guy, the radium in the center of the ball would be under very high pressure so it wouldn't boil so quickly: think of the Earth's inner core which is estimated to be at 5000+ kelvin and 3e6+ atm of pressure, and which is believed to be either solid, or a very viscous liquid. 2601:648:8202:96B0:0:0:0:5B74 (talk) 13:19, 2 August 2020 (UTC)
 * Excellent point. --Guy Macon (talk) 13:55, 2 August 2020 (UTC)

By the way, the novel Rip Foster Rides the Gray Planet (aka Assignment In Space with Rip Foster) is about the discovery of an asteroid made of pure thorium (useful as reactor fuel), and the logistics of getting it back to earth using nuclear bombs ala Project Daedalus as propellant. The book wasn't as bad as our article about it might make it sound. 2601:648:8202:96B0:0:0:0:5B74 (talk) 22:10, 2 August 2020 (UTC)
 * Because alpha radiation is a hefty part of the energy released in radium decay, and alpha rays are not very penetrating, I asked the question with radium because it would seem then that at most a small fraction(not sure) of the energy released by decay would radiate into outer space "for a while", since radium more than a few meters of the surface couldn't emit a particle that would escape. But I should have specified pure Radium 223. as suggested above, so that the "for a while" could allow enough time for almost all the radium atoms to decay, before a large fraction of the energy escapes. Now it seems that you get 25 Mev for every 2 protons with hydrogen fusion? 5 Mev from alpha emission isnt too shabby. The density of rocks at earth's surface is about 3 g/cc, the average earth density is about 5.5, and the density of the compressed iron in the core might be more than 13, or at least very high. Since radium has a density of 5.5, with the resulting compression at the radium planet's core factored in, I would think the mass of a radium planet with earth's size would be more than twice as much as earth's mass. Based on this, I might be quite crazy, but I estimate, for the first 11 days, that the energy per second from the decay of the radium planet to be about 10^13 times greater than the the energy from fusion in the sun. I will doublecheck. I hope at least some of you are interested. Is shelf 42B something to do with Douglas Adams meaning of life being 7*8=42? thanks of course to all. Rich (talk) 23:31, 5 August 2020 (UTC)
 * The meaning of life, as calculated by a supercomputer over a period of 7.5 million years, was 42. It is, of course, a constantly changing variable. To find out what the answer was a millisecond later you need to repeat the entire calculation. :( --Guy Macon (talk) 01:39, 6 August 2020 (UTC)
 * Corrected correction: I would like to change my estimate to 2X10^4 times greater energy per second than the energy from the sun(for the first few days), mainly because i forgot it was 600 million tons per second of hydrogen in the sun, not 600 tons. And some other mistakes. But this new estimate makes sense because: 600 million tons of hydrogen is about 10^-13 of an earth mass. There might be about two earth masses of radium in all. The earth's mass of radium expected to decay in 11.5 days consists of radium 223, which is about 200 times more massive than a hydrogen atom. Each radium alpha particle is "worth" 5, while each solar hydrogen atom undergoing fusion is "worth" 12.5. In 11.5 days, roughly 10^6 seconds occur. So, somewhat roughly, akin to 10^-6 of a radium earth emits its alpha particles each second. Since radium atoms weigh about 200 times as much as a proton, the ratio of Radium planet power to Sun power is [(10^-6/200) X 5]/(10^-13 X 12.5)=20,000. That’s so much energy the planet would be blown apart and scattered widely in seconds, I think.Rich (talk) 00:53, 6 August 2020 (UTC)

are prisoners in solitary confinement safer from covid than those in gen pop?
This is just a theoretical question--despite having made some crappy edits now and then, I'm not currently in prison. But I have to wonder about this. Thanks. 2601:648:8202:96B0:0:0:0:5B74 (talk) 13:10, 2 August 2020 (UTC)


 * Solitary confinement means that the prisoner is deprived of contact with other inmates and their loved ones. It does not mean they are totally isolated; in most jurisdictions they will still be allowed to see their lawyer. If they are subjected to a full body search by a prison guard after each visit by their lawyer, they may in fact be more at risk. So it is not possible to answer this as a theoretical question other than by, "it depends". As a statistical question, the data needed for analysis is lacking and is (almost certainly) not being collected for later analysis. --Lambiam 08:49, 3 August 2020 (UTC)
 * Can they read all the time? (most subjects, not just religion which is constitutional right many places) then eh so what but most prisoners are extroverts and would rather be at 24/7 risk of being stabbed for no reason by the semi-insane than be alone with a Britannica. The body search must be horrible but unfortunately necessary till they bother to be not sadistic and offer a radiational scanner, whatever can detect swallowed things and stuff with the least cancer risk, oh wait a body search can't detect swallowed things. Perhaps they could seal one of those talk through the glass things and put cameras that can't see them if they don't get too near the wall to prevent lawyer smuggling without letting anyone read their lips and not have to search at all? And of course some people in solitary confinement have no brain physiology to love anyone at all and would murder and rape without guilt if a good opportunity showed up i.e. ISIS. It might be a third or less (no idea) but for that subset of solitary fuck you. Talk to yourself if you're so bored. Sagittarian Milky Way (talk) 14:04, 3 August 2020 (UTC)
 * Is this supposed to help the questioner find an answer to their question? --Lambiam 17:46, 3 August 2020 (UTC)
 * You editorialized first, you know full well that a good chunk can't have loved ones, some are serial killers, some raped little kids etc. yet you wrote as if loved ones are assumed like a propagandist. You could've just put a (if they have any) there and it would've been scientific. Sagittarian Milky Way (talk) 00:55, 4 August 2020 (UTC)
 * I wrote this for the simple (functional, non-editorial) reason that this lack of contact reduces the risk, relative to other inmates. It was part of an "on one hand ; on the other hand ", which is clearly germane to the question. --Lambiam 20:20, 4 August 2020 (UTC)
 * The word you're looking for is "visitors", it doesn't matter if they love them, like them but no homo, want to kill them, what matters is they're extra contact with outside. Unless all visits (except lawyers I guess) are banned cause of the virus (may vary by place) in which case the only extra contact would be non-visitors and maybe staff. Sagittarian Milky Way (talk) 01:41, 5 August 2020 (UTC)
 * I wanted to avoid the term "visitor" to avoid confusion with the term "prison visitor". --Lambiam 13:49, 6 August 2020 (UTC)
 * Are you sure you can't get loved ones in solitary if you're in for protection and not punishment for something you did or allegedly did or your security level (supermax, minimum etc)? That makes no sense. Sagittarian Milky Way (talk) 01:06, 4 August 2020 (UTC)
 * It is not unheard of that a rule that is actively enforced makes no sense. --Lambiam 20:41, 4 August 2020 (UTC)
 * In fact, prisons seem to be well known for such rules. 93.136.213.247 (talk) 21:44, 4 August 2020 (UTC)
 * I've heard that in USA most of the upkeep such as cleaning and food preparation is actually done by prisoners themselves, the guards just walk around with guns and seem to have not many further responsibilities. Since prisons are not known for hygiene, I think it's reasonable to assume that while prisoners in solitary confinement are less likely to get coughed at, there's plenty of other ways they're likely to get infected. 93.136.213.247 (talk) 21:44, 4 August 2020 (UTC)