Final answer:
Soon after the universe formed, it contained more matter than antimatter. This imbalance allowed matter to remain after annihilation processes and formed the basis for the observable universe. Direct evidence from space confirms the dominance of matter over antimatter in the cosmos.
Step-by-step explanation:
The universe after its inception contained both matter and antimatter, but crucially there was a slight asymmetry; specifically, there was more matter than antimatter.
This minute difference is significant because it allowed matter to prevail after most of it had annihilated its antimatter counterpart, leaving just enough matter to form the stars and galaxies we observe in the cosmos.
The rarity of antimatter is confirmed by direct observations, such as the lack of annihilation radiation from space, indicating that our solar system, and by extension the majority of the universe, is dominated by matter.
It's also important to note that the dominance of matter over antimatter is somewhat perplexing, as the Standard Model of particle interactions doesn't show large differences in the behavior of matter and antimatter.
Yet still, the universe we see today is mostly composed of ordinary matter, which points to the extraordinary fact that in the early universe, there must have been a process that produced slightly more matter during particle decays like those of the neutral kaon.