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Any reason to suspect that these regions aren't just much larger than the observable universe?

by nol13 10y ago

hwillis 10y ago
That question is a nonstarter, essentially. Physics is interested and concerned with why the observable universe has almost no antimatter, so asking "what if all the antimatter is outside the observable universe" doesn't actually answer the question.
danbruc 10y ago
One could maybe argue that there has to be some fundamental asymmetry between matter and antimatter. If there were none, you have to find a good explanation why there was not the same amount of matter and antimatter right after the Big Bang and why therefore not all matter and antimatter just turned into photons leaving behind an empty universe. If on the other hand there is an asymmetry and matter is favored over antimatter, then the matter we see today would just be the difference left over after all the antimatter annihilated. In that case there seems to be no obvious reason why regions should form.
gus_massa 10y ago
It's reasonable to suppose that if in one experiment you replace each particle by it's antiparticle you will get the same result. (Symmetry C) The problem is that this is not true in all experiments :( It's reasonable to suppose that if in one experiment you make a mirror image of all the part of the experiments, with the mirrored version of all the velocities and spin, you will get the same result. (Symmetry P) The problem is that this is not true in all experiments :( (I'll skip T symmetry.) For some technical reason it's more easy to expect that if you combine both symmetries and change all particles by the antiparticle and make a mirrored version, you will get the same result. (Symmetry CP) This is almost almost almost true. Not completely true, but it's difficult to make an experiment where the result is different. So, in some experiments the CP version is different from the original version. It is possible to measure this in a laboratory, and this is one possible explanation of the different of the amount of mater and antimatter around us, but no one is sure about the details. See https://en.wikipedia.org/wiki/CP_violation#CP_violation_and_the_matter.E2.80.93antimatter_imbalance https://en.wikipedia.org/wiki/CP_violation#CP_violation_and_...

Any reason to suspect that these regions aren't just much larger than the observable universe?

by nol13 10y ago

Any reason to suspect that these regions aren't just much larger than the observable universe?

That question is a nonstarter, essentially. Physics is interested and concerned with why the observable universe has almost no antimatter, so asking "what if all the antimatter is outside the observable universe" doesn't actually answer the question.

danbruc 10y ago

One could maybe argue that there has to be some fundamental asymmetry between matter and antimatter. If there were none, you have to find a good explanation why there was not the same amount of matter and antimatter right after the Big Bang and why therefore not all matter and antimatter just turned into photons leaving behind an empty universe. If on the other hand there is an asymmetry and matter is favored over antimatter, then the matter we see today would just be the difference left over after all the antimatter annihilated. In that case there seems to be no obvious reason why regions should form.

gus_massa 10y ago

It's reasonable to suppose that if in one experiment you replace each particle by it's antiparticle you will get the same result. (Symmetry C) The problem is that this is not true in all experiments :( It's reasonable to suppose that if in one experiment you make a mirror image of all the part of the experiments, with the mirrored version of all the velocities and spin, you will get the same result. (Symmetry P) The problem is that this is not true in all experiments :( (I'll skip T symmetry.) For some technical reason it's more easy to expect that if you combine both symmetries and change all particles by the antiparticle and make a mirrored version, you will get the same result. (Symmetry CP) This is almost almost almost true. Not completely true, but it's difficult to make an experiment where the result is different. So, in some experiments the CP version is different from the original version. It is possible to measure this in a laboratory, and this is one possible explanation of the different of the amount of mater and antimatter around us, but no one is sure about the details. See https://en.wikipedia.org/wiki/CP_violation#CP_violation_and_the_matter.E2.80.93antimatter_imbalance https://en.wikipedia.org/wiki/CP_violation#CP_violation_and_...