Symmetry has been one of the guiding principles in physicists' search for fundamental laws of nature. What does it mean that laws of nature have symmetry? It means that laws look the same before and after an operation, similar to a mirror reflection, the same but right is now left in the reflection.
Physicists have been looking for laws that explain both the microscopic world of elementary particles and the macroscopic world of the universe and the Big Bang at its beginning, expecting that such fundamental laws should have symmetry in all circumstances. However, last year, two physicists found a theoretical proof that, at the most fundamental level, nature does not respect symmetry.
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