Gravity Wells

Gravity doesn’t work by attracting two bodies together.  That’s the result, but not the mechanism.  Gravity doesn’t work like magnetism.  Instead, a massive body distorts time and space around it, creating a dimple that other bodies fall into.  Einstein proved this by predicting that light from a distant star would temporarily change position in the night sky when another large body moved in between us and the target.  The light from the target passes by the nearer star, runs along the gravity well, and comes out in a slightly different direction.  The important distinction is that spacetime itself is warped by the mass of the star.  From your perspective, you’re still moving in a straight line, it’s space that’s curved.

When we depict gravity fields, we usually envision them as cones in a flat surface.  This is a simplification, though.  Gravity exists in a three dimensional space, not on a tabletop.  It’s easier for us to picture them in a flat space, though.  How would you represent a place at the center of the Earth where gravity doesn’t exist?  Once you’re at the center of the Earth, there’s no longer any direction you could call “down”.  Gravity doesn’t exist in any meaningful way at that point in space.  You’re in the middle of a large distortion in the universe, though you wouldn’t know it.

http://en.wikipedia.org/wiki/Gravitational_lens

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