Expert: Philip Stahl - 4/30/2009

Question
Einstain said on his theory of relativity that earth wrap the fabric of space and time to create the gravity effect.
how can i picture an object inside earth in the fabric of space and time?

Answer
Actually, you are confusing the general theory of relativity with something else. The general theory - Einstein's gravitational theory, says nothing about Earth per se, but in a generic sense relates gravitational attraction to a potential well created by the mass of a given object.

For example, the Sun as the most massive object in our solar system creates the potential well that defines and determines how and at what rates the various planets orbit around it.

Earth, in like manner, will create its own gravitational potential well, and this determines whether artificial satellites, for example, will be held in orbit and for how long. Also, the velocity needed to escape Earth gravity entirely and become a literal "space ship" like Pioneer 10.

The escape from any potential well will thus depend on achieving an escape velocity such that the object can be displaced from Earth orbit entirely. (Which is usually computed using Newtonian mechanics, and not general relativity).

My point here is that though GR defines the existence of such "potential wells" it is not needed to compute the velocity needed to escape them. Thus, we need not concern ourselves about any "fabric of space and time" for an object *inside Earth*, for which gravitational escape is a moot point anyway.

Hope this helps.