Question: how does einsteins theory of relativity

Baptiste Ravina answered on 9 Mar 2020:

…work? (gonna assume that was the question)

You may have learnt of gravity as a force, with Newton’s description of the apple falling in a straight vertical line from the tree (or the moon “falling” towards the Earth and missing it constantly, leading to what we call an “orbit”). Einstein came up with a neat idea: if you’re standing in an elevator at rest, you feel the effect of gravity; whenever it’s moving (up or down), you feel an additional acceleration. In fact, if it’s going fast enough, you can feel “lighter” or “heavier” depending on which way it’s going. Could gravity not be a force at all, but a mere acceleration?

Turns out it can! And that’s a very simple approach to general relativity: there’s no gravity force, there’s just space (space-time, actually, but it’s a bit more complicated to explain) and we’re all moving along straight lines on it. However, large masses (very large, like stars, galaxies or black holes) can deform that space-time and make it curve around them. If we’re still traveling along our straight lines in a curved space-time, it now looks like we’re actually moving around the star or galaxy! and in precisely the same way as Newton would have described using the language of forces.

Why does it help at all to think about space-time in that way? Because now we can talk about weird ways space-time itself can be arranged: black holes. And we can also talk about the past history of space-time: the Big Bang. Pretty neat.