# What exactly is Gravity?

## Recommended Posts

"What exactly is gravity?"

Gravity is the curvature of space caused by matter.

Gravity is the curvature of space spacetime caused by matter. Don't forget GR is a geometric model that encompasses time as well.

Edited by StringJunky
##### Share on other sites

The term $T^{\mu\nu}h_{\mu\nu}$ is not "unspecified" but a well-known term with precise properties. Next picture is from Feynman textbook on gravitation

I must have overlooked that picture in your earlier posts - not to mention that I still don't see a definition of h or how your claim follows from the term. I'm not even convinced that your "gravitational interaction" term actually has units of energy as you claim - but that's just silly nitpicking and doesn't really add something.

I'm not convinced that your knowledge extends beyond having seen images of equations in a book of Feynman, and you probably believe I don't even know that much. Given that we already left the part where it's about the other's opinion, I don't wish to continue this discussion.

##### Share on other sites

I must have overlooked that picture in your earlier posts - not to mention that I still don't see a definition of h or how your claim follows from the term. I'm not even convinced that your "gravitational interaction" term actually has units of energy as you claim - but that's just silly nitpicking and doesn't really add something.

As said before $h_{\mu\nu}$ is the gravitational potential. It is obtained from solving the field equations for specific problems.

It is rather simple to check that the gravitational interaction term $T^{\mu\nu}h_{\mu\nu}$ has units of energy. One way is to see that the term is found in the Lagrangian for gravitation and Lagrangians have units of energy. The second way starts from noticing that $h_{\mu\nu}$ is dimensionless (as any textbook explains) whereas the $T^{\mu\nu}$ has units of energy: [energy x dimensionless] = [energy].

## Create an account

Register a new account