12 upvotes, 3 direct replies (showing 3)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
According to Einstein’s theories of relativity, time is just another dimension, like up/down left/right forward/backward. This additional dimension gives us a four-dimensional space called spacetime.
Everything moves through spacetime at the speed of light. We aren’t quite sure why, but we understand this to be true with Einstein’s theories. The faster (and we’re talking really much faster) an object moves through space, the slower it must move through time, so that it maintains the same speed through spacetime.
It helped me to think about a car that can only move at a constant speed, say 60 mph. The car is on an infinite 2d plane. The car can move North, East, or some combination of North and East, but still can only move at 60 mph. If the car is moving at 60mph North, it is not moving East at all, and vice versa.
Now switch North with “Time”, and East with “Space”. The car can only move at the speed of light (something like 300,000 km/s). So, it can move completely in the “Time” direction (like a photon would do in a vacuum) or completely in the “Space” direction (or likely a combination of both). The more it moves through space, the less it moves through time.
That’s Special Relativity (without explanations of observers and how it all depends on how you’re actually viewing said car too).
But yeah, time as we understand today is just another axis that we move through. Only difference is that we can’t move backwards through time.
Comment by GolemancerVekk at 26/04/2023 at 19:14 UTC
7 upvotes, 1 direct replies
we can’t move backwards through time.
We can't or nothing can? And why not?
Comment by TheGrumpyre at 26/04/2023 at 22:09 UTC*
3 upvotes, 1 direct replies
So I'm gathering that the big question relativity answers is: if a photon is moving entirely in the space dimension at such a speed that it doesn't experience any passage through the time dimension whatsoever, how is it that we can perceive it moving from point A to point B in a measurable amount of our time. And it's mathy.
Comment by frankduxvandamme at 26/04/2023 at 22:26 UTC
1 upvotes, 1 direct replies
Everything moves through spacetime at the speed of light. We aren’t quite sure why, but we understand this to be true with Einstein’s theories.
What? Only light moves at the speed of light