Implication is that time passed more slowly at that time in the universe.
Or that light travelled more slowly at that time in the universe. I don't think we have conclusively proven c to be a constant, right? Or is this a case of "c and t are so inextricably linked, it doesn't matter in practice which one changes, the result is effectively the same"?
> I don't think we have conclusively proven c to be a constant, right?
We obviously can't directly test what the speed of light was 1.5 billion years after the Big Bang. But we can test for changes in the fine structure constant back then, which would have to have been different back then if the speed of light were different. No such changes have been found.
I’m going to assume the credentialed astrophysicists who came to this conclusion probably have a good reason why they didn’t go with that interpretation of things.
Or that light travelled more slowly at that time in the universe. I don't think we have conclusively proven c to be a constant, right? Or is this a case of "c and t are so inextricably linked, it doesn't matter in practice which one changes, the result is effectively the same"?