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awarded  Yearling
Nov
1
comment Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
@astromax, good point questioning whether the universe is a closed system; according to Brian Greene's The Elegant Universe book/movies the strong/weak nuclear forces and electromagnetic are in this universe, but gravity can loop outside what we perceive as 3D+time spacetime and only part of it is here, so gravity could enable interaction with multiverses
Nov
1
awarded  Commentator
Nov
1
comment Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
@astromax I also read about the big rip where even atoms will be torn apart; maybe the universe could be like a bubble that will burst; but, I don't think that things flying apart will cause them to break down at the subatomic level; says here at the bottom wmap.gsfc.nasa.gov/universe/uni_expansion.html that the universe expands by 70km/sec/mpc; if the universe has 13.7G lightyears radius = 4202 mpc then 70 * 4202 = 294140km/sec = almost 299794.458km/sec(lightspeed)so for all its acceleration, expansion is kind of asymptotically reaching its max,lightspeed,so unlikely to rip atoms apart
Nov
1
comment Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
@Moriarty my understanding is that the stable black hole mass is 3 solar masses, and that this limit is increasing as the temperature of the universe, currently 2.73 Kelvin, decreases due to expansion; so as the stable black hole mass increases, more and more black holes will convert themselves to radiation; I think of entropy as a measure of disorder - high entropy = lots of disorder; low entropy = highly ordered system; need to expend time and energy to lower entropy in one place, typically by increasing entropy elsewhere;
Nov
1
comment Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
the heat death of the universe is what I was trying to avoid; I wanted to know if what stars are doing, burning H, is a one-way deal, or if the H resource is renewable; Larry Niven said "entropy in the universe tends toward a maximum - the universe is hostile"; that must be why, at least with current technology it is easier to destroy something than make it back; it is interesting that above iron, fission gives more energy, and below iron, fusion does; but it's not clear to me how nuclear binding energy affects hydrogen - it is just a proton and electron; maybe it affects only deuterium?
Nov
1
comment Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
I like this answer(upvote), the diagram is enlightening, but cannot choose 2 answers unfortunately. en.wikipedia.org/wiki/Abundance_of_elements here we see that hydrogen and helium are 98% of all baryonic matter, so not much decay going on now. But in the far future, I agree, natural nuclear decay could likely be the dominant source for H/He like you said in your comment above. I looked up the speed of an alpha particle, and it seems like it is around 5% of light speed, 15000-20000km/sec depending on energy, so it may be going too fast to gravitationally collapse and form new stars.
Nov
1
comment Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
ok so I would like to clarify that I'm not picky about whether the hydrogen is generated from heavier elements; if it comes from other sources that is good too; what I want to get at is see whether the fuel for stars can be renewed so they can keep on shining; I would think a primary problem with protons from cosmic rays (good idea btw, upvote for that), although a hydrogen atom is a proton and an electron, if it travels at a significant fraction of the speed of light it would, I expect, find it difficult to be affected by gravitational collapse in order to form a star
Nov
1
comment Why can't light escape from a black hole?
@brentonstrine the free velocity you mention you get from a gravity assist: www2.jpl.nasa.gov/basics/grav/primer.php the orbital velocity of the Earth is about 30km/sec, it varies a bit down to 29kps because the orbit is not an exact circle, we are actually closer to the sun in northern winter and farther by about a million km in summer. nssdc.gsfc.nasa.gov/planetary/factsheet
Nov
1
awarded  Informed
Oct
31
comment Dark Matter Particle Candidates
I thought dark matter does not interact except via gravity, didn't know it uses weak nuclear force as well. But that doesn't work at a distance. To see dark matter should be all about a choice of instruments. Ordinary telescopes, both earth-based and space-based, are sensitive to various parts of the electromagnetic spectrum, detecting photons emitted by cosmic objects. To see something that interacts only via gravity, a gravity telescope is needed that can see gravity waves emitted by dark matter/energy. lisa.nasa.gov is such an example. Could dark matter be non-particle things?
Oct
31
revised Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
added image
Oct
31
accepted Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
Oct
31
suggested suggested edit on Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
Oct
31
awarded  Scholar
Oct
31
accepted How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it?
Oct
30
asked How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it?
Oct
30
awarded  Student
Oct
30
asked Is there a natural process by which hydrogen is generated from heavier elements in the cosmos?
Oct
30
comment Why can't light escape from a black hole?
escape velocity for Earth is 11.2kps; however, this applies to thrown objects; you have to throw a rock at 11.2kps (ignoring atmospheric drag) in order for it to leave the Earth and not fall back; however, if your rock has an engine that can apply thrust, it can leave the Earth at a much lesser speed. The longer it is able to apply thrust, the slower it can go when leaving.