eli5: When space-time “bends” due to gravity, what is it bending ‘inside’ of, or in respect to?

208 views

eli5: When space-time “bends” due to gravity, what is it bending ‘inside’ of, or in respect to?

In: Physics

It’s not “bending” in the sense of taking on a new dimension (like bending a straight wire into a 2D curved wire).

It’s easier to think of it as a compression of a 3D mesh. If you have a uniform 3D mesh and you think of the lines as “straight”, then if you expand once cell by filling it with “a planet” you will see the mesh lines squished together near the planet. Some lines, which hit the planet at a right angle, are shortened. This let’s you drop a rock onto the planet following these straight lines. There are also “straight” lines that bend around the planet, corresponding to your path being curved by the planet’s gravity.

Reality.

space-time is a fancy word for Reality. Everything that has, does or can exist needs to exist somewhere/when. This where/when is space-time. When space-time “bends” it just means that the Reality’s becomes non Euclidian. e.g. Two straight parallel lines DO converge.