According to the prevailing scientific understanding, the annihilation of matter and antimatter likely occurred in the early stages of the universe, shortly after the Big Bang. However, the exact timing and details of this process are still subjects of active research and investigation.
The prevailing hypothesis is that the universe began with a nearly equal amount of matter and antimatter. Matter and antimatter are composed of particles with opposite charges and other properties, such as protons and antiprotons or electrons and positrons. When matter and antimatter particles come into contact, they can annihilate each other, converting their mass into energy in the form of photons.
The phenomenon of matter-antimatter annihilation is crucial in understanding the current asymmetry between matter and antimatter in the universe. If equal amounts of matter and antimatter existed, they would have annihilated completely, leaving only energy behind. However, observations show that our universe is predominantly made of matter, with very little antimatter.
The precise moment when matter-antimatter annihilation occurred is not yet fully known, as it happened during the extremely early stages of the universe, when conditions were extremely hot and dense. Scientists believe that the annihilation process likely took place within the first moments to the first few minutes after the Big Bang. As the universe expanded and cooled down, the energy of the annihilation would have transformed into the cosmic background radiation that we can detect today.
Studying the nature of matter-antimatter asymmetry and the specifics of the annihilation process remains an active area of research in the field of particle physics and cosmology.