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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.
Oct
30
revised How does neutron star collapse into black hole?
added image