<p>To answer your second question first: Yes, antimatter does exist in the same space as matter. In fact, the universe creates antimatter (and an equal amount of matter) every day as a matter of course in events like <a href="http://www.nasa.gov/mission_pages/GLAST/news/fermi-thunderstorms.html" rel="nofollow">lightning strikes</a> and supernovae, and even in certain nuclear decays. Humans create it in particle accelerators for research and for commercial/medical applications such as <a href="http://en.wikipedia.org/wiki/Positron_emission_tomography" rel="nofollow">Positron Emission Tomography</a>. The thing is, when we create antimatter, we also create an equal amount of matter. </p>

<p>In the hot flash of energy after the Big Bang, particle-antiparticle pairs were popping into existence and annihilating each other constantly. There were almost exactly equal amounts. For some reason, though, for every 100 trillion (10^11) particles of antimatter, there were 100 trillion and one particles of matter. In the ensuing few minutes, all the antimatter and all but that tiny fraction of matter annihilated each other and turned back into energy. Everything we can see today, all the galaxies, stars, and planets, are made up of that tiny amount of matter that was left over. Particle physicists still aren't sure why there was this tiny imbalance in the amount of matter and antimatter, because all interactions we've seen so far produce equal amounts of both. This is one question particle colliders like the Large Hadron Collider are attempting to answer.</p>

CC BY-SA 4.0
2019-09-08T11:47:26.163Z
We have already experimental results showing a little antisymmetry between matter and antimatter: neutral kaons with different half life than neutral anti-kaons. The unsolved question is the details, how this little difference in the early Universe resulted this quite huge difference today.
peterh
CC BY-SA 3.0
2014-01-29T19:59:04.117Z
2014-01-29T19:59:04.117Z
gargoylezoo
<p>The universe supposedly started off with equal parts matter and antimatter and they are said to annihilate each other. Also, nature is famous for it's balance between everything. So all we see is matter and no antimatter (I guess that's a good thing, we would all have been annihilated otherwise), so where did all the antimatter go?</p>

<p>Also, does antimatter exist in the same space as matter? What are the leading theories about it?</p>

CC BY-SA 3.0
2014-01-11T12:50:31.760Z
Where indeed? Your question is known as the [Baryon Asymmetry Problem](http://en.wikipedia.org/wiki/Baryon_asymmetry). This is currently one of the major unsolved problems in physics, so it's clearly a good question for frontier physics. But since it hasn't been answered yet, there's really no point asking it here.
David H
CC BY-SA 3.0
2014-01-11T12:54:06.237Z
Ah! That's why I couldn't find an answer anywhere. I thought I had missed something. And indeed the Baryon Asymmetry Problem it was.
Ranveer
CC BY-SA 3.0
2014-01-12T14:16:10.113Z
Could probably be asked on Physics.SE, however as pointed out, there is no definitive answer yet...
Rory Alsop
CC BY-SA 3.0
2014-01-12T21:06:50.530Z
As long as we're clear that any proposed resolution to this riddle is purely speculation at this stage, I see no problem sharing my personal guess. I have a standing $8 bet with a colleague that when decipher the makeup of dark matter (which comprises 85% of matter in the Universe!) we'll find a reverse imbalance of dark matter particles to anti dark matter particles in such a way that exactly compensates the for the imbalance found in ordinary matter. Fingers crossed.
David H
CC BY-SA 3.0
2014-01-13T14:32:06.277Z
@RoryAlsop Since this question is a matter of cosmology it is firmly within scope of this site.
called2voyage
CC BY-SA 3.0
2014-01-13T16:20:04.770Z
@Ranveer I would suggest changing the question "which one is the most plausible" to "what are the leading theories". Plausibility is still somewhat subjective at this point since as others have pointed out there isn't much yet to determine the best theory from. However, we can certainly summarize the most discussed theories in the scientific community.
called2voyage
CC BY-SA 3.0
2014-01-13T16:31:08.003Z
True, changed the question :)
Ranveer
CC BY-SA 3.0
2014-01-14T05:46:43.350Z
@DavidH: I don't think that would work. For example, dark matter is abaryonic, and so m/am asymmetry in dark matter cannot solve the m/am asymmetry in baryon number. Or do you mean that DM would be involved in a new process that violates baryon number conservation and the like?
Stan Liou
CC BY-SA 3.0
2014-01-18T17:56:23.167Z
Is nature really that "balanced" - after all we have a discrete, quantum, universe, not a smooth one. These concepts - like balance - can be misleading if we apply them too rigidly
adrianmcmenamin
CC BY-SA 3.0
2015-12-04T15:49:35.803Z
See my comment on the Physics Stack Exchange here: http://physics.stackexchange.com/questions/24042/baryon-asymmetry
Lewis Miller
CC BY-SA 3.0
2015-12-06T14:54:52.910Z
Note that I have converted my comment on the PSE to an answer.
Lewis Miller
<universe><formation><matter><early-universe><antimatter>
Where is all the antimatter?
Ranveer
# Where is all the antimatter?

(Asked by: username_0 on 2014-01-11)

The universe supposedly started off with equal parts matter and antimatter and they are said to annihilate each other. Also, nature is famous for it's balance between everything. So all we see is matter and no antimatter (I guess that's a good thing, we would all have been annihilated otherwise), so where did all the antimatter go?

Also, does antimatter exist in the same space as matter? What are the leading theories about it?

**Tags:** universe, formation, matter, early-universe, antimatter

> **Comments:**
> **username_1**: Where indeed? Your question is known as the [Baryon Asymmetry Problem](http://en.wikipedia.org/wiki/Baryon_asymmetry). This is currently one of the major unsolved problems in physics, so it's clearly a good question for frontier physics. But since it hasn't been answered yet, there's really no point asking it here.  
> **username_0**: Ah! That's why I couldn't find an answer anywhere. I thought I had missed something. And indeed the Baryon Asymmetry Problem it was.  
> **username_2**: Could probably be asked on Physics.SE, however as pointed out, there is no definitive answer yet...  
> **username_1**: As long as we're clear that any proposed resolution to this riddle is purely speculation at this stage, I see no problem sharing my personal guess. I have a standing $8 bet with a colleague that when decipher the makeup of dark matter (which comprises 85% of matter in the Universe!) we'll find a reverse imbalance of dark matter particles to anti dark matter particles in such a way that exactly compensates the for the imbalance found in ordinary matter. Fingers crossed.  
> **username_3**: @username_2 Since this question is a matter of cosmology it is firmly within scope of this site.  
> **username_3**: @username_0 I would suggest changing the question "which one is the most plausible" to "what are the leading theories". Plausibility is still somewhat subjective at this point since as others have pointed out there isn't much yet to determine the best theory from. However, we can certainly summarize the most discussed theories in the scientific community.  
> **username_0**: True, changed the question :)  
> **username_4**: @username_1: I don't think that would work. For example, dark matter is abaryonic, and so m/am asymmetry in dark matter cannot solve the m/am asymmetry in baryon number. Or do you mean that DM would be involved in a new process that violates baryon number conservation and the like?  
> **username_5**: Is nature really that "balanced" - after all we have a discrete, quantum, universe, not a smooth one. These concepts - like balance - can be misleading if we apply them too rigidly  
> **username_6**: See my comment on the Physics Stack Exchange here: http://physics.stackexchange.com/questions/24042/baryon-asymmetry  
> **username_6**: Note that I have converted my comment on the PSE to an answer.  

---

## 1 answers

### Answer by username_7 on 2014-01-29. Score: 4

To answer your second question first: Yes, antimatter does exist in the same space as matter. In fact, the universe creates antimatter (and an equal amount of matter) every day as a matter of course in events like [lightning strikes](http://www.nasa.gov/mission_pages/GLAST/news/fermi-thunderstorms.html) and supernovae, and even in certain nuclear decays. Humans create it in particle accelerators for research and for commercial/medical applications such as [Positron Emission Tomography](http://en.wikipedia.org/wiki/Positron_emission_tomography). The thing is, when we create antimatter, we also create an equal amount of matter.

In the hot flash of energy after the Big Bang, particle-antiparticle pairs were popping into existence and annihilating each other constantly. There were almost exactly equal amounts. For some reason, though, for every 100 trillion (10^11) particles of antimatter, there were 100 trillion and one particles of matter. In the ensuing few minutes, all the antimatter and all but that tiny fraction of matter annihilated each other and turned back into energy. Everything we can see today, all the galaxies, stars, and planets, are made up of that tiny amount of matter that was left over. Particle physicists still aren't sure why there was this tiny imbalance in the amount of matter and antimatter, because all interactions we've seen so far produce equal amounts of both. This is one question particle colliders like the Large Hadron Collider are attempting to answer.

> **Comments:**
> **username_8**: We have already experimental results showing a little antisymmetry between matter and antimatter: neutral kaons with different half life than neutral anti-kaons. The unsolved question is the details, how this little difference in the early Universe resulted this quite huge difference today.  

---

