Why/how is light the fastest thing in the universe and nothing else can be faster?

Question

Why have we ruled out the possibility of finding something faster when we’ve only scratched the surface of space exploration and understanding?

In: 144

Answer 1

For something to go faster than light, it would have to go backwards in time.

Space and time are linked according to our best model for the universe. The faster something moves, the slower time passes for it relative to everything else. When we take 2 very accurate watches and send one to space to orbit the Earth for a while, it will be behind the one left back on earth. Time stops entirely for something traveling the speed of light. Light takes 1.3 seconds to travel from the earth to the moon from our standpoint, but from the light’s standpoint the trip happened in an instant. Any faster than that and it’ll move backwards in time.

It may be possible to go backwards in time for all we know but that seems highly unlikely. Causality starts to break down if that were allowed to happen.

What if I said “If I see someone on the moon light a green light, I’ll send a faster than light signal for him to light a red one.” while the moon light operator has instructions to keep it green unless instructed to turn it red. If the message gets there faster than light then it goes backwards in time to before I actually send it. Meaning when I look at the moon it’ll already have a red light. But if it has a red light already I’d never send the instruction to turn it red, meaning it should have stayed green. Which is it? Maybe such an event would create it’s own fork into two separate universes, one for each outcome. It seems much more likely that it just can’t happen.

It could very well be that our best model for the universe is missing some key piece of information that allows faster than light travel. I don’t think it’s fair to say the possibility is ruled out completely. Someone would have to put forth a new model of the universe that fits all the observations better though. Since our current model has withstood a lot of tests for a while now, that doesn’t seem likely.