system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 how do we know nothing is faster than light?
gpt
The branch of physics that deals with things going really fast (special relativity) breaks if you go faster than light. Masses & energies head for infinity, time stops working, total weirdness ensues.

It's \*possible\* that this is a math artifact of an incomplete model but the special relativity equations have been proven to an astonishing degree of accuracy so, right now, all evidence says they're correct and no evidence says they're wrong (at least about the speed of light part).

Basically, \*if\* you can go faster than light, there's a whole branch of physics that's totally incompatible with everything we currently understand. It's possible but there's currently no evidence for that (and a huge amount of evidence against it).

We know we can't push a regular object up to light speed because that takes infinite energy and we don't have that. That's not quite the same as not being able to have something that's already going faster than light and just stays there, but it's not even clear how we'd detect something like that (and we have no idea how to create it).