# Physics/Gravity question.?

I had to explain gravity to someone, and that actually got me thinking of something pretty interesting. We all know that gravity is the tendency of two objects with non-zero mass to accelerate towards each other, and that the greater mass an object has, the less it accelerates in comparison to other objects. Two... show more I had to explain gravity to someone, and that actually got me thinking of something pretty interesting.

We all know that gravity is the tendency of two objects with non-zero mass to accelerate towards each other, and that the greater mass an object has, the less it accelerates in comparison to other objects. Two Apples in zero gravity will "meet halfway", and the same is true for Earth and a falling object: Earth will move towards the object, but in such a minuscule amount it is virtually undetectable.

So the question is: if everyone on the northern hemisphere of Earth jumped over and over again, how long would it take for a noticeable shift in Earth's position relative to it's original position, (i.e. for Earth to move in our direction enough to be noticeable via observation), considering the massive difference in mass between us and the Earth, and assuming that the Earth is not revolving around the sun, but is isolated from any other celestial body?
Update: Bridget: Clearly you do not understand how gravity works. I explained that Earth does accelerate, but in a very minuscule amount. I was asking how long it would take for a noticeable movement (assuming no other variables/stupid technical sh!t like "how would they survive with no sun" [which I'm sure... show more Bridget: Clearly you do not understand how gravity works. I explained that Earth does accelerate, but in a very minuscule amount. I was asking how long it would take for a noticeable movement (assuming no other variables/stupid technical sh!t like "how would they survive with no sun" [which I'm sure someone will answer with]), NOT EVEN that the acceleration would increase; I never said that--it goes without saying that each time everyone jumps, the earth would accelerate towards them, but not keep its momentum. The question is simply a factor of how long it would take for a noticeable shift to finally take place. Please gtfo if you don't know what you're talking about.
Update 2: Matt: You also seem to be oblivious to the mechanics of gravity, the Earth does accelerate when you jump, just by a very small amount, the number is not 0. No stupid/ignorant answers pl0x.
Update 3: Matt: Also, you have the wrong idea of that law. The law of equal and opposite reactions describes what happens when, say, a car suddenly starts accelerating with you in it, or you decide to punch a wall really hard; the force will have an opposite reaction, effectively reflecting the shock (you get thrown back,... show more Matt: Also, you have the wrong idea of that law. The law of equal and opposite reactions describes what happens when, say, a car suddenly starts accelerating with you in it, or you decide to punch a wall really hard; the force will have an opposite reaction, effectively reflecting the shock (you get thrown back, the shock waves go into your arm and injure you), NOT that Earth will go towards, and then back away when you jump (seriously, that's just stupid). What you are implying is that when the Earth was forming, ever time a rock smashed into it, it bounced right back off, which is false (Nothing would have formed), the force of gravity outweighs the force of momentum, so your argument is terribly invalid.