Science
05 Mar 14
09 Mar 14
Originally posted by humyI meant the possibility that anti-matter repels other anti-matter.
If it repels then we would have surely already observed this with the antimatter experiments but we didn't observe this. In addition, even if it does 'repel' matter, antimatter still annihilated matter in the experiments so, evidently, it doesn't 'repel' well enough, at least in all our experiments to date, to stop contact and annihilation thus this still begs ...[text shortened]... to mention the several other significant problems with the idea of dark matter being antimatter)
09 Mar 14
Originally posted by Metal BrainWe can make anti-matter in small quantities but have not seen any such thing at least so far.
I meant the possibility that anti-matter repels other anti-matter.
My feeling is anti-matter would not go anti gravity on us, I don't think the mass inside makes any difference to the curvature of spacetime.
10 Mar 14
1 edit
Originally posted by Metal BrainRepel how? Do you mean via electro-magnetism, in which case positrons repel other positrons, but there's nothing special about that since electrons repel electrons as they have the same charge. Or do you mean gravitationally? The main question that I've heard asked is whether anti-matter repels matter gravitationally, not whether it repels other anti-particles. I don't think that anyone seriously expects there to be an unknown force which causes anti-particles to repel each other and the known forces don't behave like that.
I meant the possibility that anti-matter repels other anti-matter.
10 Mar 14
Originally posted by FabianFnasI think the answer is, at least in practical everyday terms, we wouldn't notice any difference.
Question:
If we would live in a universe completely made up of anti-matter (as ours are made up of ordinary matter) - would it then be different from ours? Would we even notice it? (...provided that all the others constants are the same?)
But I have heard of some as yet unproven theory that the behavior of antimatter may be in some way very subtly and very slightly different from that of matter ( "matter-antimatter asymmetry" ) and, if so, there may be some experiment that allow us to measure that difference albeit with difficulty.
10 Mar 14
Originally posted by humyLook up CP violation on Wikipedia. This is the asymmetry between matter and anti-matter you are thinking of. This doesn't require "new physics", it happens in the standard model and has been experimentally observed (in the 1960s) but the consequences aren't all clear - for example it appears not to be strong enough to account for the fact that there is a lot more matter than anti-matter.
I think the answer is, at least in practical everyday terms, we wouldn't notice any difference.
But I have heard of some as yet unproven theory that the behavior of antimatter may be in some way very subtly and very slightly different from that of matter ( "matter-antimatter asymmetry" ) and, if so, there may be some experiment that allow us to measure that difference albeit with difficulty.
10 Mar 14
Originally posted by DeepThoughtThe same way gravity attracts matter. Call it anti-gravity.
Repel how? Do you mean via electro-magnetism, in which case positrons repel other positrons, but there's nothing special about that since electrons repel electrons as they have the same charge. Or do you mean gravitationally? The main question that I've heard asked is whether anti-matter repels matter gravitationally, not whether it repels other anti- ...[text shortened]... rce which causes anti-particles to repel each other and the known forces don't behave like that.
10 Mar 14
Originally posted by Metal BrainI would think they would have seen that in the concentration of anti-matter where it would in that case be repelled by the massive gravity in the center of galaxies and individual stars.
The same way gravity attracts matter. Call it anti-gravity.
The report is there is quite a bit of anti-matter right here in our solar system and there are even designs afoot to capture such local anti-matter collectors between here and the moon.
11 Mar 14
Originally posted by Metal BrainThe question of whether anti-matter is gravitationally attracted or repelled by anti-matter is an experimental one. Since anti-matter has positive energy and mass I see no reason why it should behave differently to normal matter in a gravitational field. I doubt that there is any way of distinguishing between matter and anti-matter based solely on their gravitational behaviour. My opinion is based on theory, there hasn't yet been an experiment, but I am confident that anti-matter falls down and not up.
The same way gravity attracts matter. Call it anti-gravity.
12 Mar 14
1 edit
Did Dark Matter Kill the Dinosaurs?
http://www.scientificamerican.com/article/did-dark-matter-kill-the-dinosaurs/
"The solar system's periodic passage through a "dark disk" on the galactic plane could trigger comet bombardments that would cause mass extinctions."
Is this a mere speculation or is it credible?
