Antimatter - could it ever be utilized as poss. energy source?

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  • #26
Tom Mattson
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Nenad said:
I mean surrounding temp, not temp of a photon.
In that case, what you wrote is not correct. Pairs can be produced in deep space, where the average temperature is about 3 Kelvin.
 
  • #27
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heres a link, scroll down to pair production. Youll see what I mean: http://instruct1.cit.cornell.edu/courses/astro101/lec32.htm [Broken]
 
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  • #28
Tom Mattson
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Nenad said:
heres a link, scroll down to pair production. Youll see what I mean: http://instruct1.cit.cornell.edu/courses/astro101/lec32.htm [Broken]
OK, I see. The link is discussing the early universe in which there is a "sea" of photons. In an environment in which the universe is awash in radiation, the energy of the radiation field determines the ambient temperature. So in that case, there is a correletion between temperature and pair production. But in a way this hides the real quantity that determines the thresholds for pair production, and that quantity is photon energy.

Today, the universe is awash in weak radiation (with a temp of about 3K, as I said). As is known from QFT and from experiment, pair production is a quantum phenomenon, and as such it only takes a single photon to produce a pair in the Coulomb field of a heavy nucleus. It is the energy of this single photon that determines the thresholds for pair production, and it does not matter what the surrounding temperature is.
 
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Im just stationg what the site says. I trust Cornell, theyre a good university. But you do have a point.
 
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Tom Mattson
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Nenad said:
Im just stationg what the site says. I trust Cornell, theyre a good university. But you do have a point.
To be sure, Cornell is trustworthy. But that site is meant to be a layperson's introduction to the early universe, not a tutorial on particle physics.
 
  • #31
Entropy said:
Maybe for spacecrafts but thats about it. You need to create the actual anti-matter first which raises the question, where do you get the energy to create the anti-matter?

But wouldn't the anti-matter react negatively to the matter?
 
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alexkerhead said:
But wouldn't the anti-matter react negatively to the matter?
Im not sure what you mean by "react negatively" but matter and antimatter annihilate each other when they touch, in other words they get converted completely into energy. So, we WANT them to "react" with each other, because the energy relased from it is a very good prepelant for spaceships if we had a sufficient quantity of antimatter. If we eventually make antimatter propeled spaceships, we could reach to almost the speed of light.

Tom Mattson said:
Today, the universe is awash in weak radiation (with a temp of about 3K, as I said). As is known from QFT and from experiment, pair production is a quantum phenomenon, and as such it only takes a single photon to produce a pair in the Coulomb field of a heavy nucleus. It is the energy of this single photon that determines the thresholds for pair production, and it does not matter what the surrounding temperature is.
I was wondering...how come its possible for ONE photon to get converted into an electron-positron pair, while when the electron-positron pair annihilate, they are ALWAYS converted into TWO gamma rays with equal energy in opposite direction, in order to conserve energy and momentum. Doesnt the fact that one photon can be converted into the pair in a sense violate conservation of momentum?
 
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ArmoSkater87 said:
I was wondering...how come its possible for ONE photon to get converted into an electron-positron pair, while when the electron-positron pair annihilate, they are ALWAYS converted into TWO gamma rays with equal energy in opposite direction, in order to conserve energy and momentum. Doesnt the fact that one photon can be converted into the pair in a sense violate conservation of momentum?
Yes it does, and that's why the photon does not create a pair all by itself. Pair production from a single photon is done in the presence of a Coulomb field, often that due to a heavy nucleus. The nucleus recoils after the production, and so is able to conserve both energy and momentum in the process.
 
  • #34
Im not sure what you mean by "react negatively" but matter and antimatter annihilate each other when they touch, in other words they get converted completely into energy. So, we WANT them to "react" with each other, because the energy relased from it is a very good prepelant for spaceships if we had a sufficient quantity of antimatter. If we eventually make antimatter propeled spaceships, we could reach to almost the speed of light.
Thanks for the clear up...
I see now..
I was really under the close minded impression that when they reacted, they would disappear..lol

I understand, thanks for clearing it up..

But the idea has been around for decades..
If we could develope an efficient way of space travel, anti-matter could be found, but would be hard to collect and manage..
 
  • #35
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alexkerhead said:
Thanks for the clear up...
I see now..
I was really under the close minded impression that when they reacted, they would disappear..lol
Thats why everything that happens must obey the conservation laws :smile:. If they disapeared without geting converted into anything, that would violate the conservation of mass and energy, E=mc^2. Momentum must be conserved as well, which is why then regular and anti particles annihilate to create 2 gamma rays going in opposite directions.

If they just I understand, thanks for clearing it up..

But the idea has been around for decades..
If we could develope an efficient way of space travel, anti-matter could be found, but would be hard to collect and manage..
People are trying to detect anti-atoms now as a sign of anti-stars, but havnt found any. Which means that they either dont exist (not likely), or they are extreamly far. Even at the speed of light, it would take too long to get there, let alone collect and contain it, and then bring it back.
 
  • #36
And light speed is not acheivable yet..
and most likely will not..
If I read Einstein's work correctly..
 
  • #37
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You did, the speed of light will never be reached or surpassed, even relative to another velovity. But people will eventually be able to have "warp drive". It sounds like something from Star Trek, lol and it is, but science fiction always has a potential of becoming science fact. Although it would get us places faster than light could, it would still obey Einsteins laws.
 
  • #38
It is odd, a lot of stuff, scientifically is actually somthing that was theorized on the original star trek, and the newer next generations...kind wierd eh?
acceleration to lightspeed is impossible due to the fact the mass becomes finite, based on the velocity/mass curve..correct?
 

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