I’m sure I’m not really understanding gravity theory, but I have in mind the illustration of marbles on a bedsheet. If that bedsheet is space-time, why isn’t there some sort of universal up and down as objects relate to each other?
In: Planetary Science
We visualize gravity using a 2 dimensional model where space-time is a flat sheet that is distorted by objects pressing, as you say, “down” on them.
But space-time is actually 4 dimensional (3 spatial dimensions plus time), and it’s impossible for us to visualize that. “Down” in a 4 dimensional system is incomprehensible. The only way we can really work with it is mathematically.
Think about this: a black hole, i.e. a hole in spacetime, is actually a sphere.
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