# Gravity, and were it starts.

1. Mar 5, 2012

### fellupahill

Thanks for darrackth(or whatever his username is. Im on my phone so its hard to look) for the quote that got me thinking

Where does the gravity come from tho? If gravitons exist(Do they have to for the standard model to work?) then what produces the gravitons? All the matter? or just the matter on the edge of the solid mass object? Why is the gravity strongest at the center? If gravity is pulling matter and energy twords itself how does gravity work "inside" the planet. If we carved a room out of the earth near the core and found a way to get down inside, what would the gravity be like in that room? Is the force still pulling twords the center? And whats at the very centerpoint of gravity ?
I know that was alot of questions, and I don't expect someone to answer them all individually. It would be awesome if someone could take my post, see how im looking at gravity and provide some insight to clarify the things I need clarifying on :)

2. Mar 5, 2012

### Staff: Mentor

Gravity is extremely well described by Einstein's Theory of General Relativity. According to GR mass and energy both warp or bend spacetime, which manifests itself to us as the force of gravity. If you are searching for a "why" beyond this then science cannot help you, as there is nothing else that accurately describes gravity.

This highly depends on what you mean by saying "strongest". The greatest concentration of mass is at the Earths core, so on a volume basis it would have the most gravity. HOWEVER...

...inside the Earth you have gravity pulling you in all directions. If you are in the very middle of the core you still experience time dilation but you do NOT feel a NET force in any direction because the Earth is pulling you equally in all directions. Note that this is not saying you don't feel any gravity, as you still experience time dilation, it's just that the force of gravity is equal in every direction, leading to no net pull.

3. Mar 5, 2012

### Jonathan Scott

Gravitons are currently just a vague idea, as at present there is no theory which includes both quantum mechanics and general relativity.

When you refer to the "strength" of gravity, you need to distinguish between the gravitational potential (loosely, how "deep" it is) and the acceleration or force (loosely, how "steeply sloping" it is).

In both Newtonian gravity and in general relativity, there is no gravitational force inside a spherically symmetrical hollow. It's at a lower potential than outside, but there's no "slope".

4. Mar 6, 2012

### fellupahill

Im doing a halfway terrible job of explaining myself. Im gunna think about it abit more then get back to you with a rephrasing.

"inside the Earth you have gravity pulling you in all directions. If you are in the very middle of the core you still experience time dilation but you do NOT feel a NET force in any direction because the Earth is pulling you equally in all directions. Note that this is not saying you don't feel any gravity, as you still experience time dilation, it's just that the force of gravity is equal in every direction, leading to no net pull." Very informative.

5. Mar 6, 2012

### Cosmo Novice

Yes just remember gravity is not confined to planets/suns. All objects with mass have a gravitational curvature on spacetime. The Sun, Earth and Moon are our most obvious examples of spacetime curvature, while gravity is the weakest fundamental force it can also dominate such as in the Solar system. Remember though that even the pen on my desk curves spacetime and therefore has a gravitational "force" - it is just much less than the Earth because it is not as massive.

Hope this helps.