Baryon Asymmetry
A major question that physicists often ask is why there is so much more matter than antimatter in the universe. This is known as the Baryon Asymmetry problem. The expected outcome of the big bang would be to create equal amounts of matter and antimatter that will destroy each other and leave behind a universe consisting only of radiation. Obviously, this was not the case. |
. source: http://www.dailygalaxy.com |
The most prominent explanation is that the process involved with the big bang somehow favored the creation of matter over antimatter. There are other less supported explanations such as the theory that there is another part of our universe that consists mostly of antimatter. |
 source: https://www.research.vt.edu/resmag/sciencecol/physics1.html |