Another 600 pointer: most people in space are actually experiencing about 1/4 the Earth’s gravity (although they don’t feel it). So, knowing this, when does Earth’s gravity no longer have influence on you?
Never.
Well, if you want to be technical, the earth always has some influence, even at great distances. It may be negligible, but it has some effect.
*Originally posted by Jeff Waegelin *
**Well, if you want to be technical, the earth always has some influence, even at great distances. It may be negligible, but it has some effect. **
Sorry. That’s exactly what I meant.
When you are infinitely far from the earth, of course. Now, as to realistic possibilites … that’s another matter 
Actually Stephen, if you are infinately far from Earth, you’ll still fell it’s gravity (and quit deviding by zero!). Jim, you get your 600 points.
Actually recent discoveries have showed that changes in gravity have a response rate that is approximately equal to the speed of light. Theoretically, then, if you could travel faster than the speed of light, you could eventually break free from all effects of the Earth’s gravity.
I win 
is “when you’re dead,” too much of a metaphysical answer?
…just sayin’.
*Originally posted by EddieMcD *
**Actually Stephen, if you are infinately far from Earth, you’ll still fell it’s gravity (and quit deviding by zero!). Jim, you get your 600 points. **
The force of gravity, if you take Newton to be correct, is given by GMm/r^2. As r (distance from center of earth) increases without bound, the force approaches 0. Thus, when the object if infinitely far away, the force is 0 (and the only division by 0 would be if I were in the center of the earth).
But, if you take the theory of Special/General Relativity into account, Newton’s equation is no longer sufficient. Einstien viewed gravity as a bend in space time, not an actual force. This bend in space time is on a local level, however, and thus when one is infinitely away from the earth, he does not expirience its gravity. Also, Jnadke is correct too, stating that you can escape gravity by “outrunning” it. I must admit I don’t have a complete understanding of the relativity theories, though, so I may be misconstruing some facts.
Stephen
I suggest reading Steven Hawking’s A Brief History of Time. I did so for an English paper and it was rather intriguing.
There are 4 forces associated with the atom on a quantum level, weak, strong, electromagnetic, and gravitational. On a quantum scale, the electromagnetic forces prevail. On a massive scale, the gravitational forces far outweigh the others. That’s why physicists are having such a hard time these days.
Gravity is a manefestation of the trillions of atoms that make up the earth creating an equal pull on eachother, and on you. No matter where you are, you’d feel it. If you were at the center of the earth, you’d be pulled in all directions. The forces would be so strong that it would pull you apart.