Matter and antimatter are essentially the same, except for the opposite charge of their constituent particles. Matter is composed of particles such as electrons, protons, and neutrons, which have specific properties such as mass and charge. Antimatter, on the other hand, consists of antiparticles that have the same mass as their corresponding particles but opposite charge. For example, the antiparticle of an electron is called a positron, and it carries a positive charge.
The process of annihilation occurs when matter and antimatter particles come into contact with each other. When a particle and its antiparticle meet, they annihilate, releasing energy in the form of gamma rays or other particles. This process converts the mass of the particles into pure energy, according to Einstein's famous equation E=mc², where E represents energy, m represents mass, and c represents the speed of light.
As for why all matter did not get annihilated by antimatter a long time ago, this question relates to one of the biggest mysteries in physics known as the baryon asymmetry problem. According to our current understanding of the universe, matter and antimatter should have been produced in equal amounts during the early stages of the universe, shortly after the Big Bang. However, observations indicate that our universe is predominantly made up of matter, with very little antimatter.
The reason for this imbalance is not yet fully understood, and it remains an active area of research. Scientists have proposed various theories and mechanisms to explain this disparity, such as violations of fundamental symmetries (known as CP violation) or differences in the behavior of matter and antimatter particles. These hypotheses are still being tested and studied through experiments and observations.
It's important to note that the scarcity of antimatter in our universe does not mean that antimatter cannot exist or be produced. Antimatter can be created in particle accelerators or observed in certain high-energy processes, but it is extremely rare compared to matter. The question of why there is more matter than antimatter in the universe is a fundamental puzzle that researchers are actively working to solve.