What happened to all the Anti-Matter

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Main Question or Discussion Point

I recall that the absence of Anti Matter used to be a concern to Cosmologists, has this situation changed in recent years perhaps with the discovery of a slight assymetry between the two? What is the current understanding?
 

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  • #2
phyzguy
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The current understanding is that there was a slight asymmetry and the universe produced slightly more matter than antimatter. Then after the matter and antimatter annihilated into photons, we were left with photons and matter. Today in the universe there are about 10^9 photons for every baryon, so it is believed that the slight asymmetry was about 1 part in 10^9. However, I believe that the cause for this slight asymmetry, that led to more matter being created than antimatter, is not fully understood.
 
  • #3
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Thanks phyzguy, yes I think that was how I recall the situation.

I believe Kopio was attempting to help explain some of this but I think it has been shelved.

http://www.bnl.gov/rsvp/KOPIO.htm [Broken]
 
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  • #4
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Please delete this post if it is considered crackpot to suggest that antitime and antimatter are living happily ever after in another universe...
 
  • #5
Chalnoth
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The current understanding is that there was a slight asymmetry and the universe produced slightly more matter than antimatter. Then after the matter and antimatter annihilated into photons, we were left with photons and matter. Today in the universe there are about 10^9 photons for every baryon, so it is believed that the slight asymmetry was about 1 part in 10^9. However, I believe that the cause for this slight asymmetry, that led to more matter being created than antimatter, is not fully understood.
Yup. The Wikipedia article on Baryogenesis provides a pretty good overview of the subject.
 
  • #6
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Oldfart are you suggesting negative space and time in anti matter universe creating at the same time as ours? As in Star Trek?
Unfortunately it is something which likely can never be proven so it is just imaginative speculation.
 
  • #7
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Oldfart are you suggesting negative space and time in anti matter universe creating at the same time as ours? As in Star Trek?
Unfortunately it is something which likely can never be proven so it is just imaginative speculation.
Not really suggesting, more like idly wondering if such a thing could be possible. But like you say, I guess we'll never know...
 
  • #8
The current understanding is that there was a slight asymmetry and the universe produced slightly more matter than antimatter. Then after the matter and antimatter annihilated into photons, we were left with photons and matter. Today in the universe there are about 10^9 photons for every baryon, so it is believed that the slight asymmetry was about 1 part in 10^9. However, I believe that the cause for this slight asymmetry, that led to more matter being created than antimatter, is not fully understood.
yes, it is very disappointing that there is no good theories why there was an asymmetrical distribution of matter and antimatter when the universe was 'born'. that is a very interesting question.
 
  • #9
Chronos
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My opinion:
Matter and antimatter were created in equal amounts, but gravity caused a slight abundance of matter in some regions of the universe and of antimatter in other regions. Gravity would attract matter to matter, and attract antimatter to antimatter, but repel matter from antimatter, causing matter to clump nearer to other forms of matter. Because gravity is weaker than the other forces, it would only create a small asymmetry.
 
  • #11
Chalnoth
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My opinion:
Matter and antimatter were created in equal amounts, but gravity caused a slight abundance of matter in some regions of the universe and of antimatter in other regions. Gravity would attract matter to matter, and attract antimatter to antimatter, but repel matter from antimatter, causing matter to clump nearer to other forms of matter. Because gravity is weaker than the other forces, it would only create a small asymmetry.
This doesn't work with what we know about the early universe.

At the time the cosmic microwave background was emitted, some 13.7 billion years ago when our universe was just a few hundred thousand years old, our universe was completely uniform in all directions to one part in one hundred thousand. Some parts were a little less dense, some parts a little more dense, but overall it was just one smooth soup of matter. At that time, it was fundamentally impossible for the normal matter and the anti-matter to be physically separated. It was only much later, when matter clumped into galaxies, that we had localized clumps of matter separated by vast expanses of nearly empty space.

There's also the problem that even with some repulsive force, every once in a while a normal matter gas cloud would collide with an anti-matter gas cloud, unleashing a stream of gamma ray particles that we could see here on Earth. We've been looking for quite some time, and have seen no indication of any such events.
 
  • #12
Nabeshin
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My opinion:
Matter and antimatter were created in equal amounts, but gravity caused a slight abundance of matter in some regions of the universe and of antimatter in other regions. Gravity would attract matter to matter, and attract antimatter to antimatter, but repel matter from antimatter, causing matter to clump nearer to other forms of matter. Because gravity is weaker than the other forces, it would only create a small asymmetry.
In addition to what is explained in Chalnoth's post, this simply isn't how antimatter works. Matter and antimatter respond to gravity identically.
 
  • #13
856
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Was any anti matter created at all during the big bang and inflation era?

Are we talking about an almost equal amount of anti protons, neutrons, hydrogen, and helium that was annihilated into energy and then back to matter/anti matter again many times until the last of the anti matter dissappeared from the universe?
 
  • #14
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I think the only honest answer to the direct query made is: good question, nobody has a clue, just guesses and hopes. I wouldn't expect to be alive for a conclusive answer to BB Nucleosynthesis.
 
  • #15
Chalnoth
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Was any anti matter created at all during the big bang and inflation era?
At the end of inflation, matter and anti-matter were produced in equal quantities. Later, CP violation effects caused the amount of matter to ever so slightly exceed the amount of anti-matter, resulting in some amount of matter left over once all of the anti-matter had annihilated.

Are we talking about an almost equal amount of anti protons, neutrons, hydrogen, and helium that was annihilated into energy and then back to matter/anti matter again many times until the last of the anti matter dissappeared from the universe?
Not atoms, no. At the time most of the annihilation was going on, our universe was a quark-gluon plasma, without even any identifiable protons or neutrons, let alone atoms. As the temperature fell, protons and neutrons condensed out of this quark-gluon plasma.
 
  • #16
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At the end of inflation, matter and anti-matter were produced in equal quantities. Later, CP violation effects caused the amount of matter to ever so slightly exceed the amount of anti-matter, resulting in some amount of matter left over once all of the anti-matter had annihilated.


Not atoms, no. At the time most of the annihilation was going on, our universe was a quark-gluon plasma, without even any identifiable protons or neutrons, let alone atoms. As the temperature fell, protons and neutrons condensed out of this quark-gluon plasma.
Still need that CP violation in the lab though...
 
  • #17
Chalnoth
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Still need that CP violation in the lab though...
Well, we have seen some. The degree of CP violation that we have seen so far doesn't explain the matter/anti-matter asymmetry, but the fact that we have seen some makes this a very strong candidate for explaining the matter/anti-matter asymmetry.
 
  • #18
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Well, we have seen some. The degree of CP violation that we have seen so far doesn't explain the matter/anti-matter asymmetry, but the fact that we have seen some makes this a very strong candidate for explaining the matter/anti-matter asymmetry.
I didn't know that, and all I have to say is: cool. I do want to say, I wasn't casting aspersions on the theory, I just noted that the LHC crowd is waiting for something more, and this is one of those "mores". I gather it would be right up there with anything that has "Higgs" in the name.
 
  • #19
Chalnoth
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I didn't know that, and all I have to say is: cool. I do want to say, I wasn't casting aspersions on the theory, I just noted that the LHC crowd is waiting for something more, and this is one of those "mores". I gather it would be right up there with anything that has "Higgs" in the name.
The CP Violation Wikipedia article is pretty good for what we know about this so far:
http://en.wikipedia.org/wiki/CP_violation

But yes, finding a process with sufficient CP violation to explain the matter/anti-matter symmetry would indeed be a tremendous discovery.
 

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