How a clock in outer space moves more quickly than a clock on Earth
In: Physics
Imagine you and a friend stand together in a big open field and one of you starts sprinting as fast as possible due East and the other due north. You are both running as fast as possible and are equally matched so you are both running the same speed too.
As you sprint due East, all of your motion is to the East – you are not going north at all. Your buddy? All of his motion is to the north, he’s not moving to the East at all.
Maybe instead you sprint toward “2 o’clock” and he sprints toward “1 o’clock” and so this time you are both making progress in both the north and east directions. You’re both running the same speed, but you are moving faster to the east than your buddy but slower to the north. Your buddy is moving faster to the north but slower to the east.
Now take this big open field and call it “spacetime” (one word) and instead of “east” the direction is called “time” and instead of “north” the direction is called “space”.
All of us and everything around us – you, me, your cat, your toaster, are all at once moving through “spacetime” at a constant speed – the fastest speed possible (called “the speed of light”) and all of that speed is split between space and time (east and north so to speak).
So the faster something is moving through space (“to the north”) the slower it is making progress through time (“to the east”) and vice versa.
So it’s not that the clock (“time”) moves differently in space simply because it’s in space, rather, because it is orbiting and moving through space much faster than the one stuck on earth, less of its motion is through time and so the clock ticks slower. (Gravity and space curvature play a role too but this is ELI5)
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