# What is gravity?

1. Apr 5, 2012

### Nash Su

How does gravity work? I want to know where gravity comes from on the atom and how it attracts other matter towards it. Also the black hole gravity is so strong that not even light can escape it. Does this mean that light is being lightly bend when it passes another star/planet?

2. Apr 5, 2012

### phinds

Yes.

Technically, light is bent by ANY object with mass, but of course unless the mass is large, the amount of bend is negligible.

I personally bend light all the time, but like many of my efforts, the effect is negligible.

3. Apr 5, 2012

### Staff: Mentor

This is a very big subject. Currently our main theory of gravitation is General Relativity. GR says that mass and energy cause a curvature of spacetime which results in objects "attracting" each other. The reason why this results in an attraction is fairly technical and involves a lot of math you most likely have never seen or heard of before. I don't even know it very well myself, so I cannot explain it.

Anything with mass or energy will gravitate, so the force isn't being "emitted" by a specific spot on an atom, but by the whole atom. (Or, if you prefer, from each subatomic particle that composes the atom)

Interestingly, one of the first tests of Einsteins Genral Theory of Relativity was to measure the change in the path of light around the Sun during an eclipse.

4. Apr 6, 2012

### haruspex

Just to clarify a possible misunderstanding for the reader: It's not that the eclipse changed the path of the light. It would have changed anyway, but the eclipse made it observable.