Physics is local. The speed of light is a derivative of that general principle.
I’m not sure I follow this. A purely Newtonian universe with no gravity (to keep things simple) would have completely local laws and no speed of light limit.
When you say “[a] purely Newtonian universe with no gravity,” do you mean a universe in which light doesn’t exist at all as a trivial counterexample to the above claim? Or do you actually have in mind some more complex point?
I was interpreting speed of light in this context to mean that there’s a maximum speed in general otherwise the claim becomes trivially false. In that regard, the claim isn’t true and one could make a universe that was essentially Newtonian, had some sort of particle or wave that functioned like light that didn’t move instantaneously but could move at different speeds. (Actually now that I’ve said that I have to wonder if the post I was replying to meant that locality implied that light always had a finite speed which is true.) I suspect that you can get a general result about a maximum speed if you insist on something slightly stronger than locality, by analogy to the distinction between continuous functions and uniformly continuous functions but I haven’t thought out the details.
I’m not sure I follow this. A purely Newtonian universe with no gravity (to keep things simple) would have completely local laws and no speed of light limit.
When you say “[a] purely Newtonian universe with no gravity,” do you mean a universe in which light doesn’t exist at all as a trivial counterexample to the above claim? Or do you actually have in mind some more complex point?
I was interpreting speed of light in this context to mean that there’s a maximum speed in general otherwise the claim becomes trivially false. In that regard, the claim isn’t true and one could make a universe that was essentially Newtonian, had some sort of particle or wave that functioned like light that didn’t move instantaneously but could move at different speeds. (Actually now that I’ve said that I have to wonder if the post I was replying to meant that locality implied that light always had a finite speed which is true.) I suspect that you can get a general result about a maximum speed if you insist on something slightly stronger than locality, by analogy to the distinction between continuous functions and uniformly continuous functions but I haven’t thought out the details.
Oh, I see. Thanks for the explanation.