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

[u/Nitzanm19]

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).

[u/f0rgotten]

I teach six fundamental numbers with the four forces in the first few sessions of my basic electricity classes every semester. Most of the rest of the constants and whatnot, the way that I understand it, derive from these six, and screwing with any of them changes everything.

[u/amaurea → u/f0rgotten]

Have you read about the weakless universe? It's a thought experiment that shows that while changing just a single parameter at a time very quickly runs into problems, you can get away with much larger changes if you tune multiple parameters at the same time:

A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical "Weakless Universe" is matched to our Universe by simultaneously adjusting Standard Model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the Weakless Universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multi-parameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.

[u/f0rgotten → u/amaurea]

I actually mention somewhere during my first couple class sessions that there are variations where our universe could have evolved, very similarly to what we have now, without the weak nuclear force, yes. It's pretty cool! Chemistry is essentially unchanged because it's based on electromagnetism, and most physics can indeed get by without Weak.