Category: CPT

This Is The One Symmetry That The Universe Must Never Violate

“In physics, we have to be willing to challenge our assumptions, and to probe all possibilities, no matter how unlikely they seem. But our default should be that the laws of physics that have stood up to every experimental test, that compose a self-consistent theoretical framework, and that accurately describe our reality, are indeed correct until proven otherwise. In this case, it means that the laws of physics are the same everywhere and for all observers until proven otherwise.

Sometimes, particles behave differently than antiparticles, and that’s okay. Sometimes, physical systems behave differently than their mirror-image reflections, and that’s also okay. And sometimes, physical systems behave differently depending on whether the clock runs forwards or backwards. But particles moving forwards in time must behave the same as antiparticles reflected in a mirror moving backwards in time; that’s a consequence of the CPT theorem. That’s the one symmetry, as long as the physical laws that we know of are correct, that must never be broken.”

Are the laws of physics the same, here and now, as they are at all other times and places in the Universe? If they are, then that means a certain symmetry exists. It appears, to up to 18 orders of magnitude in some experimental cases, that specific symmetry is good and respected by our Universe. If a theory demands its violation, that theory is presently unsupported by all of the evidence. The reason? 

One particular symmetry, known as CPT, that the Universe forbids us from violating.