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What it says on the title. How come all the positrons don't destroy all the electrons in the universe and vice versa? They are attracted to each other due to opposing charges.

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  • $\begingroup$ This entire question is based on the assumption that the number of positrons and electrons is not only equal, but also that they are both distributed uniformly throughout the universe - which, experimentally, does not appear to be the case $\endgroup$ Commented Dec 19, 2020 at 7:00
  • $\begingroup$ The equal amount assumption results from the one-electron universe postulate. And the non-unified distribution assumed to become unified by the fact that these two particles should be constantly attracting each other. $\endgroup$
    – lmaksms
    Commented Dec 19, 2020 at 7:17
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    $\begingroup$ That postulate is quite the assumption. You'd better add this to the question. $\endgroup$
    – NDewolf
    Commented Dec 19, 2020 at 12:27

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This is a subset of the open problem in theoretical physics, generally known under the title "baryon asymmetry"

If particles and antiparticles are created in equal numbers, one would expect there should be as many antiprotons as protons and as many positrons and electrons created at the beginning , for example in the Big Bang model, so there should be equal matter and antimatter in the present universe.

This would answer your questions, i.e. some positrons would bind with some antiprotons into antihydrogen, while electrons would bind with protons into hydrogen, and that is why all would not annihilate again, assuming a statistical probability for hydrogen to coagulate into matter clusters and antihydrogen into antimatter clusters. So not all would disappear.

BUT observations are quite clear that there are no antimatter regions in the observable universe, which means that for some physics unknown reason more hydrogen was created keeping the electrons bound to the proton.

An excess of positrons has been detected in our galactic neighborhood, I do not know if this is true for the intergalactic spaces, it would be hard to detect.

Your question gives me the impetus to ask a question about this.

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I found the answer on Cern's website. I am leaving it here for the archive. Thanks to whoever gave this question thumbs down.

https://home.cern/science/physics/matter-antimatter-asymmetry-problem

"This is what we see today. In the past few decades, particle-physics experiments have shown that the laws of nature do not apply equally to matter and antimatter. Physicists are keen to discover the reasons why. Researchers have observed spontaneous transformations between particles and their antiparticles, occurring millions of times per second before they decay. Some unknown entity intervening in this process in the early universe could have caused these "oscillating" particles to decay as matter more often than they decayed as antimatter.

Consider a coin spinning on a table. It can land on its heads or its tails, but it cannot be defined as "heads" or "tails" until it stops spinning and falls to one side. A coin has a 50-50 chance of landing on its head or its tail, so if enough coins are spun in exactly the same way, half should land on heads and the other half on tails. In the same way, half of the oscillating particles in the early universe should have decayed as matter and the other half as antimatter."

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