Antimatter

[Choobus]

Not quite fishface. Nuclear reactions (fission or fusion) only release a small amount of rest mass energy, something like a few percent, because it is simply the difference in the binding energy between the parent and daughter neuclei. Only a matter-antimmater reaction can convert all of the rest mass into energy. Thus, a matter-antimatter reaction is to a nuclear reaction as a nuclear reaction is to a chemical reaction. Complete mass conversion of a small bullet would be similar to the power of a small nuclear warhead.

Have they ever made an anti-atom? I know we got the reverse particles needed (positrons, p-bars, anti-neutrons(?), etc.) but I don't know if we've ever constructed an anti-Hydrogen or something.

[Choobus]

brad89 wrote

Have they ever made an anti-atom? I know we got the reverse particles needed (positrons, p-bars, anti-neutrons(?), etc.) but I don't know if we've ever constructed an anti-Hydrogen or something.

Yes, antihydrogen was made at CERN. I worked on that project as a graduate student, but I graduated 2 years before they actually did it. The hard part is trapping it so you can study it.

neutral particles don't have antiparticles (neutrons, photons). Or, you could say that they are their own antiparticles. Either way, they cannot annihilate.

Choobus wrote

neutral particles don't have antiparticles (neutrons, photons). Or, you could say that they are their own antiparticles. Either way, they cannot annihilate.

Wait, if a neutron is composed of quarks, and quarks have antiquarks, how come the neutron can't have an antineutron composed of the neutron's quarks' corresponding antiquarks? (Whew!)

[Choobus]

Evil_Mage_Ra wrote

Wait, if a neutron is composed of quarks, and quarks have antiquarks, how come the neutron can't have an antineutron composed of the neutron's quarks' corresponding antiquarks? (Whew!)

sorry, you're right, I should not have said neutrons. They do have anti-quarks and can annihilate. The thing is it's really hard to detect becaus ethey have no charge, but it has been done. Strictly speaking, an particle can only be its own antiparticle if it's quantum numbers all add up to zero, like a photon. A funny old beast is a neutral pion, because it's really made up out of a quantum superposition of quarks that can be interpreted as a mixutre of a positive and a negatice pion. That means even though it is made of quarks it has quarks and antiquarks, so the total is zero and if you reverse everything you get the same thing.

however, mea culpa on the neutrons.

I'm curious as to how chemistry would work if it were all antimatter. I figure it would work the same way, H2O, CO2, Fe2O3, etc., but I am just guessing. Are there any theories as to the behavior of anti-chemistry? I know we couldn't really make enough antimatter to observe any chemistry between it, but I just wondered what they thought theoretically.

um..okay..all i can tell you off thetop of my head is that it is the opposite of matter and soemthing about giant explosions if not contained properly. But thats about all.

[Choobus]

As far as we know, the chemistry of antimatter (with no matter around) would be indentical to matter. That's one of the main reasons for doing antimatter research. We think it's entirely symmetrical, and that means the fact that the universe seems to be entirely matter with little or no antimatter is a bit of a mystery. If, however, we were to discover even a small difference then that might explain it. So far we have not seen any differences. However, nodody has ever measured the gravitational effects. Maybe antimatter will fall up. Probably not, but untill we measure we won't know for sure. Tha is a fucking difficult experiment, but with a BEC of positronium and a Mach-Zender interferometer it might be doable.

[Tenspace]

Just curious, Choob. What would happen if your containment device in the lab failed? Would it blow you to a million choobits?

[Choobus]

Tenspace wrote

Just curious, Choob. What would happen if your containment device in the lab failed? Would it blow you to a million choobits?

what do you mean if?

I get irradiated by gamma rays every day. In fact the basis of our experimentatrion is to store up 100 million positrons or so and then kick them out of the trap and smash them into something. The total energy converted into gamma rays is about 1.9E-5 joules, enough to run a 120Watt lightbulb for almost a microsecond. Somebody should explain this to Dan "shitsucker" Brown.

[Tenspace]

So all those little positrons in the trap are capable of the equivalent of a nasty shock? So, if the trap failed prior to your streaming them into a target, it's not something that would leave a crater. I feel better now.

[Choobus]

Tenspace wrote

So all those little positrons in the trap are capable of the equivalent of a nasty shock? So, if the trap failed prior to your streaming them into a target, it's not something that would leave a crater. I feel better now.

If you took all the antimatter that has even been created by humans you still wouldn't be able to do much more damage than a well aimed fist.

Choobus wrote

http://www.cmr.wsu.edu/keck/science.html

here's something I wrote a few years ago

Choobus, I read your article. It took me about three hours to read it all. I don't think I comprehended everything totally because I am not a physicist, but you explained it so well I got the hint of it.
Extremely interesting article.
Thank you for sharing it with us. :)

Choobus, what about "far-away galaxies of antimatter"? Doesn't it seem like even if they were created in equal quanitites, there just wouldn't be the opportunity/time for every single piece of antimatter to react with every single piece of matter? Is it possible that there are antimatter galaxies more than 14 billion light years away?

[Tenspace]

Hmmm.... is it possible, maybe through some bizarre twist in inflation, that the balancing annihilations just haven't reached this corner of the universe yet? :O