Matter vs antimatter

  • #1

Main Question or Discussion Point

When more matter collides with less antimatter, is all of the antimatter and matter destroyed, or just equivalent amounts, and if the latter, what happens to the excess matter?
 

Answers and Replies

  • #2
phyzguy
Science Advisor
4,547
1,483
Only equal amounts annihilate. If I combine 10 electrons and 5 positrons, the 5 positrons will annihilate with 5 of the electrons, giving two photons for each annihilation. So I will be left with 10 photons and 5 electrons.
 
  • #3
So what happens to the 10 photons and 5 electrons that are left. Are they affected by the energy given off by the mutual annihilation of the others? Likewise, if these anti-matter entities are actually hydrogen and anti-hydrogen, will the same thing happen?
 
  • #4
mathman
Science Advisor
7,819
433
The ten photons are the energy of the annihilation.

Hydrogen and anti-hydrogen collision will have two parts (1) proton and anti-proton and (2) electron and positron.
 
  • #5
OK, let me put it this way: If a cloud of 100 hydrogen atoms meets a cloud of 50 anti-hydrogen atoms, what will be the result?
 
  • #6
phyzguy
Science Advisor
4,547
1,483
The end result will be 50 hydrogen atoms and a bunch of radiation. As to what happens to the remaining hydrogen atoms and the radiation, they just go on their merry way. If they are in empty space, the radiation propagates away at the speed of light, and the hydrogen atoms fly off on whatever trajectory they have (of course at less than the speed of light).
 
  • #7
So there is no effect at all on the surviving atoms? Has this been proven mathematically and/or experimentally?
 
  • #8
phyzguy
Science Advisor
4,547
1,483
It all depends on how densely packed the initial configuration is. If the outgoing energetic photons which are created in the annihilation reactions strike some of the remaining atoms, they will of course ionize them. But if the initial configuration is not very dense, then the photons will probably just free-stream out and leave the remaining atoms behind.
 
  • #9
So way back 13. something billion years BP, stuff was really stuffed compactly. Since there is almost no anti matter around now, one could assume that the ratio of matter to anti matter in the beginning was - what? a billion to a billion and one? Would that kind of mostly mutual annihilation have caused the Big Bang and the expanding universe we see today? And then there's the conundrum of it expanding FTL because the space between clumps/strings of matter is expanding FTL. Hmm. Why would space expand that fast? What's driving it?
 
  • #10
mathman
Science Advisor
7,819
433
So way back 13. something billion years BP, stuff was really stuffed compactly. Since there is almost no anti matter around now, one could assume that the ratio of matter to anti matter in the beginning was - what? a billion to a billion and one? Would that kind of mostly mutual annihilation have caused the Big Bang and the expanding universe we see today? And then there's the conundrum of it expanding FTL because the space between clumps/strings of matter is expanding FTL. Hmm. Why would space expand that fast? What's driving it?
Current theory assumes that there was no initial difference between the amount of matter and the amount of antimatter. The current lack of antimatter presumable comes from some differences in decay mechanism, associated with cp violation. However no one has yet figured out the details.
 
  • #11
According to Science News (12/18/10), in a recent CERN experiment (called ALPHA), a stream of antiprotons were supercooled into a cloud of about 40,000 particles that were then nudged into 2,000,000 positrons chilled to 40 kelvins. About 10% of the time they formed anti-hydrogen atoms. How does this compare with ratios of successful hydrogen formation using protons and electrons?
 
  • #12
If only equal amounts of matter and antimatter annihilate, then why would the explosions be so large?
 
  • #13
Drakkith
Staff Emeritus
Science Advisor
20,853
4,598
If only equal amounts of matter and antimatter annihilate, then why would the explosions be so large?
An annihilation between anti particles and real particles convert the entirety of the REST MASS of the particles to energy. This is about 100 times more energy than a typical fusion reaction releases. So every annihilation would release the same energy as 100+ fusion reactions.

From wikipedia: The reaction of 1 kg of antimatter with 1 kg of matter would produce 1.8×1017 J (180 petajoules) of energy (by the mass-energy equivalence formula E = mc²), or the rough equivalent of 43 megatons of TNT. For comparison, Tsar Bomb, the largest nuclear weapon ever detonated, reacted an estimated yield of 50 megatons, which required the use of tens of kilograms[citation needed] of fissile material (Uranium/Plutonium) (hundreds for the full-yield 100 megaton design), and two tons of lithium deuteride (fusion fuel).[35]
 
  • #14
I get the Big Bang part and that a matter/antimatter explosion might have caused it. But the other thread I was exploring was - what if anti-matter is inherently less stable than matter? Would that explain why we can't find much anti-matter in the universe? So my question is still out there: Has anyone addressed the difference in the abilities of matter and anti-matter particle clouds to form atoms?
 
  • #15
Drakkith
Staff Emeritus
Science Advisor
20,853
4,598
I get the Big Bang part and that a matter/antimatter explosion might have caused it. But the other thread I was exploring was - what if anti-matter is inherently less stable than matter? Would that explain why we can't find much anti-matter in the universe? So my question is still out there: Has anyone addressed the difference in the abilities of matter and anti-matter particle clouds to form atoms?
As far as I know there is no difference in anti-matter and normal matter that would cause it to be less stable or have a difference in forming atoms. But I'm not an expert.
 
  • #16
mathman
Science Advisor
7,819
433
As far as I know there is no difference in anti-matter and normal matter that would cause it to be less stable or have a difference in forming atoms. But I'm not an expert.
Although the mechanism is not known yet, it is assumed that there is some difference in the decay processes of antimatter particles as compared to matter particles. The difference is presumed to be the reason there was matter left over after the big bang.
 
  • #17
Well, then, that certainly would be a neat experimental research project for young physicists looking to answer one of the universe's great mysteries.
 
  • #18
Drakkith
Staff Emeritus
Science Advisor
20,853
4,598
Although the mechanism is not known yet, it is assumed that there is some difference in the decay processes of antimatter particles as compared to matter particles. The difference is presumed to be the reason there was matter left over after the big bang.
Either that or something to do with their creation is different.
 
  • #19
Either that or something to do with their creation is different.
What do you mean by that?
 
  • #20
Drakkith
Staff Emeritus
Science Advisor
20,853
4,598
What do you mean by that?
I mean that maybe their is something that is different about creating anti-matter compared to creating matter at very high energies. I don't believe there is any evidence of anti matter and matter being different in creation or decay as of yet however. Definately an interesting area.
 
  • #21
phyzguy
Science Advisor
4,547
1,483
I get the Big Bang part and that a matter/antimatter explosion might have caused it. But the other thread I was exploring was - what if anti-matter is inherently less stable than matter? Would that explain why we can't find much anti-matter in the universe? So my question is still out there: Has anyone addressed the difference in the abilities of matter and anti-matter particle clouds to form atoms?
You shouldn't view the annihilation of matter and antimatter as having "caused" the big bang. We believe that the universe is expanding from an initial state that was extremely hot and dense, much hotter and denser than the explosion that would be caused by the annihilation of ordinary matter and anti-matter. It was a "soup" of particles, antiparticles, and radiation, all in thermal equilibrium. As the temperature fell below the rest energy of various particles, they would "freeze out". If there was perfect symmetry between matter and anti-matter, at the end of this process, there would be nothing left but radiation. However, for reasons not well understood, it appears that there were slightly more particles than antiparticles, by about 1 part in 10^9. So after things cooled below the rest energy of protons, there remained approximately 1 proton for every 10^9 photons. But the energy of the big bang was imparted long before the final annihilation of most of the matter and antimatter.
 
  • #22
OK folks, let's disconnect cause/effect for matter/anti-matter and the Big Bang. What about experimental or observational evidence for the hypotheses that (a) matter and antimatter can potentially be created in almost equal amounts except that antimatter keeps being annihilated by the slightly larger amounts of matter and that (b) initial conditions for the universe were a mega-dense and hot soup of particles held in thermal equilibrium?
Roger Penrose and Vahe Gurzadyan posit that the Big Bang is only the latest in a series, or cycle, of creations and further claim that they have found evidence for it in rings of lower temperature variability in cosmic microwave background data (Nov. 17 article posted at arXiv.org).
Another question: Has all the matter in the universe been around since the Big Bang, or is more appearing "out there?"
And a clarification request: Cosmic expansion is FTL because what's expanding are the giant bubbles of nothing between the cosmic frameworks of matter. Right?
 
  • #23
38
0
An annihilation between anti particles and real particles convert the entirety of the REST MASS of the particles to energy.
Do we know the detail steps of the annihilation reaction? How to make particle--anti-particle bond and make zero mass state?
make bond------> unite one -----> some state -----> zero mass + space disappearing + energy release
What does happen after the unit one step?
 

Related Threads on Matter vs antimatter

  • Last Post
Replies
3
Views
2K
Replies
9
Views
5K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
9
Views
2K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
7
Views
3K
  • Last Post
Replies
10
Views
2K
Top