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Welcome to our Physics lesson on Prevalence of Matter over Antimatter, this is the sixth lesson of our suite of physics lessons covering the topic of Formation of Galaxies and Solar System. Actual Problems, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
All reliable physical theories support the idea that an equal amount of matter and antimatter were originally produced in the Universe. This means that at the first instants of its existence, the Universe contained same number of positive and negative charges. However, when the process of the number of particles freeze took place at the first second after the Big Bang, a number of extra matter particles survived over antimatter, creating a misbalance between them. This means that since that time there were more particles than antiparticles available; otherwise the entire matter would have disappeared in one-to-one annihilating processes with antimatter. The reason why by the end of the first second of Universe there were more matter than antimatter is still an enigma to be solved.
The most plausible explanation for this issue is the lack of symmetry in weak interaction. Let's explain what this means.
Physical laws are such that if during the occurrence of a phenomenon all the signs of electric charges change (this is called the action C) and we change the direction of occurrence from left to right and vice-versa (the action P), we obtain a new phenomenon which has the same probability of occur to the original phenomenon. Hence, we say these two phenomena possess the CP symmetry. In weak interaction however, this symmetry does not exist, i.e. a phenomenon may occur more often than the reverse one. Using this reasoning, scientists believe that the process of particles formation has had a higher probability than the reverse process of antiparticles formation during the first second of Universe's existence. Hence the difference in number between particles and antiparticles at this instant.
During the annihilation processes of matter and antimatter a very large number of photons were produced. The ratio of photons to matter particles in the Universe is related to the original particles-antiparticles difference at the first second of the Universe. This ratio is about 109:1 (one billion to one). This means that today there are about one billion times more photons than particles of matter in the Universe. All models must reach this conclusion to be considered as successful.
You have reached the end of Physics lesson 22.12.6 Prevalence of Matter over Antimatter. There are 7 lessons in this physics tutorial covering Formation of Galaxies and Solar System. Actual Problems, you can access all the lessons from this tutorial below.
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