Like how can time move slightly faster when i’m somewhere else? Also how, like in interstellar, a day on our planet was like 1,4 seconds on that one planet? I can’t seem to wrap my head around the concept of that…
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This is the nearest I personally get to an explanation I can vaguely understand*: Because movement through space and time are like opposite ends of a seesaw (AmE teeter-totter). More of one, less of the other.
General Relativity sees time as effectively a dimension, like the three spatial ones we know. And the four are bound together into something we call “spacetime”. If you want to say where something in spacetime is, you need to know not just where it is in space but, but where in time as well. So “my chair now”, say, is a different place to “my chair at this time tomorrow”.
We all understand that in some way we’re all moving through time. In spacetime, you get from “my chair now” to “my chair at this time tomorrow” by moving in time, just like you’d expect – but because we’re treating it as just another dimension, you can put a “speed” on how fast you move, just like you can measure how fast you walk. And you can combine speed through space and speed through time to get a speed through spacetime. And the amazing, beautiful thing is that, the way the universe works, you **always get the same answer** when you do. **Everything** moves through that combined thing, spacetime, at the identical speed. And it’s the one we usually call “the speed of light”.
That means that something that is motionless in space is, in a very literal sense, hurtling through time at the speed of light. But it also means that, if it starts moving in space, it won’t and can’t move through time quite as fast – because the numbers have to balance. More space movement, less time movement. The faster it goes through space, the slower it goes through time. And if it could ever get to the speed of light, it would stop moving through time altogether (which is one explanation of why nothing physical that we’re familiar with can ever move faster than light – it wouldn’t be able to go slower through time than a dead stop, basically).
(It’s not easy to get our heads around things like this, because we’ve never experienced it personally – and never will. Objectively, we’ll always measure our time as moving at the same speed. It’s just when we compare ourselves with other things that the weird stuff happens.)
* *(Beyond the facts that (a) it’s fairly easy to show that it has to work like that if the speed of light is a constant, and (b) we have done many, many experiments to show that, yes, it does).*
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