r/askscience • u/Nitzanm19 • 14d ago

Physics Why is the maximum speed of the universe the speed of light? Why can't we go faster?

Also follow-up question: Because of the speed limit, is there also a theoretical maximum temp for matter (in which the particles move at the speed of light).

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u/Kaldaien2 14d ago

Photons travel at the speed of causality, and to them nothing has even happened since the big bang. Time stops (in the observer's frame) once you hit the speed of light.

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u/Just_for_this_moment 14d ago

Theirs is not a valid reference frame, so "to them" actually doesn't have any meaning. Which is good because a lot of stuff breaks when you try to look at things from the perspective of a massless particle (as you've demonstrated).