Wikipedia:Reference desk/Archives/Science/2023 August 21

= August 21 =

Icequake
How much methane would it take to either (a) cause an explosion of Earth's entire atmosphere, or (b) explode with the same energy as that of the biggest volcanic eruption which had ever happened in Earth's history? Would it be possible for this amount of methane to be released into the atmosphere if either (a) all of the permafrost in Alaska had melted, or (b) if all permafrost in the entire world had melted, or (c) if all of the methane from all sources (including deep-underground sources) had somehow escaped into the atmosphere? 2601:646:9882:46E0:419:F6DA:6858:7015 (talk) 04:38, 21 August 2023 (UTC)
 * You need at leats 4.4% in volume of methane in air to get an explosion. The density ratio of methane to air is about 16:29 and the Earth has about 5.15·1018kg of air, so that's about 1.25·1017kg of methane. Our article on methane clathrate mentions 5–25·1014kg of carbon in methane clathrates on the sea floor, 2.3·1014kg of carbon in natural gas reserves, 4·1014kg of carbon in methane clathrates in permafrost in the Arctic (only a small fraction of which is in Alaska) and an unknown amount in permafrost in the Antarctic. The mass of methane is 5/4 times that of carbon. Even the highest estimates are a factor 32 too low to cause the entire atmosphere to explode. The resulting greenhouse effect would be more than enough to worry about.
 * We don't know that much about the biggest volcanic eruption in the Earth's history. Very little is on record about volcanic eruptions more than 100 million years ago, big eruptions don't put out all their energy in a single explosion, some don't explode at all but just produce a lot of lava. PiusImpavidus (talk) 10:33, 21 August 2023 (UTC)
 * Thanks! So, the answer to the first question is "no" -- but would it be possible for methane in the atmosphere to explode with the same energy as the total energy of the eruption(s) which created the Flat Landing Brook Formation?  Because an explosion of that size (whether methane, volcanic or otherwise) would indeed cause total devastation within a wide region (in fact, it would make the Tsar Bomba seem like a firecracker!) 2601:646:9882:46E0:AC4B:990B:D3F3:99DE (talk) 10:53, 22 August 2023 (UTC)

Animals' evolved fear of humans
I hhavevheard that wild animals avoid humans, so as long as humans don't go looking for trouble, there is little reason for us to need to carry weapons to kill them. But I wonder, since instinctual avoidance of humans can't happen for no reason at all. If humans stop hunting bears and wolves, will the avoidance of humans decrease over time? I'm supposing that any species can quickly evolve a fear for another particular species, as a handydevice in the genetic toolkit, and also deevolve the fear if it stops being selected for.136.36.123.146 (talk) 04:55, 21 August 2023 (UTC)
 * Actually, instinctual avoidance of humans does happen for no reason at all. In any group of animals, there will be a wide range of natural responses. Some will approach humans with no fear, perhaps with curiosity. Some WILL show fear. And such behaviour is at least partly hereditary. If the humans do pose a threat, the animals they kill will be those who showed no fear. Those who were fearful and held back, may survive, and pass that successful gene onto their offspring. HiLo48 (talk) 06:20, 21 August 2023 (UTC)
 * you said on your page you have been accused of being pedantic. Sorry but it's worse than that. Certainly you don't have ill intentions, but you have confused everything. Don't you see that the natural selection for fearfulness and "holding back" did in fact "happen for a reason?"2607:FB91:3F19:52E7:D84:5E50:181D:CCC (talk) 17:48, 23 August 2023 (UTC)
 * Apart from instinctual avoidance of humans, there's also learned avoidance. The wild animals may see others of their group killed by humans, may be non-lethally hurt by humans or humans may simply do unexpected things, making the animal feel less in control. If uncertain, stay away.
 * Having said that, wolves have recently returned to Western Europe and it turns out that they're not particularly afraid of humans, certainly less so than when they were actively hunted 150 years ago. Some nature photographers threw down some meat on the heath to get a nice picture of a wolf and one of those quickly learned that humans can be an easy source of food and began approaching, reportedly even chasing, humans. PiusImpavidus (talk) 11:09, 21 August 2023 (UTC)
 * Unlike the wolves there are still many easily-spooked horses thousands of years after they stopped being eaten by the megafauna that made them paranoid. I've noticed that roaches have different personalities, some freeze and let a fingertip pad creep well inside guaranteed hand pounce range before they switch their "strategy" to flee. The most scared flee like maniacs before I've even walked within reach much less started reaching yet. I think I'm unintentionally increasing mean roach fear and lowering the percent of medium to low fear. Sagittarian Milky Way (talk) 22:13, 21 August 2023 (UTC)
 * To be fair to horses, it wasn't that long ago that we stopped eating them (much, I've eaten horsemeat in Belgian restaurants). Their domestication is thought to have begun by their being corraled as a meat and milk animal, before we learned how to ride them and later use them as draught animals. {The poster formerly known as 87.81.230.195} 51.198.140.169 (talk) 13:04, 22 August 2023 (UTC)
 * I've never (knowingly) had horse meat. What does it taste like? Beef? Chicken? ←Baseball Bugs What's up, Doc? carrots→ 16:37, 22 August 2023 (UTC)
 * It has a richer flavor and texture than beef and tastes like a mix of lamb and venison. The taste of horse meat can vary depending on how the animal was raised and slaughtered. In general, it has a flavor that is described as gamey or beef-like... Make of that what you will. Alansplodge (talk) 18:27, 22 August 2023 (UTC)
 * What happens to Triple Crown winner meat? Sagittarian Milky Way (talk) 18:31, 22 August 2023 (UTC)
 * pet food. Graeme Bartlett (talk) 22:28, 22 August 2023 (UTC)
 * Really? That's not very capitalistic. Mummify it and put it in a museum or at least hold a funeral banquet and charge admission. The feast of champions! Sagittarian Milky Way (talk) 22:38, 22 August 2023 (UTC)
 * I guess breeding the fear down to cavalry charge levels wasn't a priority for most purposes. How effing scared were they at max danger though! (Pleistocene?) Sagittarian Milky Way (talk) 15:11, 22 August 2023 (UTC)
 * What about answering the question I asked in the beginning?2607:FB91:3F19:52E7:D84:5E50:181D:CCC (talk) 21:27, 23 August 2023 (UTC)
 * So you're the same as 136.36.123.146? In any case, it seems like you're requesting speculation. ←Baseball Bugs What's up, Doc? carrots→ 23:15, 23 August 2023 (UTC)
 * yes im the same, aka richard peterson. so did i err in asking for speculation??i didn't realize, and you are the omly person who has finally said so.2607:FB91:3F02:9361:3417:62BE:C15A:38E3 (talk) 19:24, 24 August 2023 (UTC)

Oort cloud size
Oort cloud remarks that The orbit of the Sun through the plane of the Milky Way sometimes brings it in relatively close proximity to other stellar systems. If the Oort cloud is as great as 3.2 light years in diameter, and Alpha Centauri is 4.2465 light years away, how are the farthest-out Oort cloud objects not attracted away by Alpha Centauri and other nearby stars? Is it simply a matter of the Oort cloud objects not being in the right place at the right time (e.g. they're on one side of the Sun and Alpha Centauri is on the other, 7.5 light years apart), or is there some better explanation? Of course I understand that the Sun could hold onto its comets against Alpha Centauri if it has a greater gravitational pull, but the two stars' infoboxes use different mass measurements (the Sun is 1.9885×1030 kg and Alpha Centauri is 1.0788±0.0029 M☉), so I'm unclear which is larger. Nyttend (talk) 22:44, 21 August 2023 (UTC)
 * M☉ means mass of sun, so 1.0788±0.0029 M☉ is bigger. However, even if gravity attracts an object, it is moving with an initial velocity, and then is probably in a hyperbolic orbit, and will then escape from the gravity of the attractor. It may be scattered in some direction away from the path of the Sun, and then be lost from the cloud. Graeme Bartlett (talk) 23:52, 21 August 2023 (UTC)
 * Oort cloud actually mentions a radius of 3.2 ly, not diameter, so your doubt makes sense. A footnote tells that this number is vague and and could also be a factor 4 lower. The radius is defined by the Sun's Hill sphere, which varies as visiting stars come and go.
 * α Centauri is a triple star system with a combined mass of 2.11 M☉, at a distance of about 4.2 ly from the sun. That gives the Sun a Hill sphere with a radius of about 2 ly. An object at 3.2 ly from the Sun in the direction of Centaurus cannot be currently gravitationally bound to the Sun. In the opposite direction, towards Perseus or Cassiopeia, the energy of such an object would be more than enough to escape to the α Cen system, but by the time that this object in its chaotic orbit reaches the saddle point, α Cen will be long gone and the Sun's Hill sphere may have grown. Objects at 3.2 ly from the sun still have a good chance of returning to the inner solar system. Obviously, Oort cloud objects get lost to interstellar space all the time. Similarly, if α Cen has its own Oort cloud, the Sun could steal comets from there.
 * Nobody has ever observed an object in the Oort cloud that far away. Even a big one can only be observed when it approaches the sun to within a few lightdays (in which case it's no longer in the Oort cloud). PiusImpavidus (talk) 09:07, 22 August 2023 (UTC)
 * The vast majority of the Alpha Centauri's mass is about 4.4 light years away not the 4.2X of the red dwarf. If just the Sun and an insignificant mass like a comet the Sun has an attraction of (1/2)**2 or 0.25 compared to at 1 light year. Even 2.45 light years from Alpha Centauri AB wouldn't be enough to balance the weak solar pull at 2 light years. The Hill sphere is well within the balance point but the Sun started with so many comets it doesn't particularly matter that zillions have been lost, there's still zillions left. The Sun has surely gained some from stars who lost theirs too. And only a few have to survive at such distance to count as Oort cloud, an inner solar system comet from that distance doesn't necessarily have to be a common occurrence. No astronomical body has even been seen at ≥19.0 light hours and the furthest observed comet with a tail or even just a coma is much closer. All searches for Planet Nine have failed and it's at least the size of a super-Earth and about 2.3 to 4.6 light days. Sagittarian Milky Way (talk) 18:24, 22 August 2023 (UTC)