what causes gravity on earth?

Force of Gravity = (mass of both objects) / (the distance between them, squared)

If you change the mass of the objects, or if you change the distance between them, you'll change the force that gravity is exerting on the objects.

This is why gravity decreases as you leave Earth.

The same thing that causes gravity everywhere else, mass.

For gravity on Earth to change the mass of the planet would have to change or the radius of the planet would have to change.

There is gravitational force between any and every two objects. You can place two apples on a table and there will be a gravitational force between them. Not nearly enough to be noticeable, but it's there.

The bigger/more dense an object is, the higher its gravitational pull is. The earth is just massive, and its core is very very dense. Therefore, it has enough gravitational force to draw things in to it.

Gravity can't change, but the amount of gravity can if an object gets more or less dense (for example, a collapsed star).

Earth's own mass causes gravity on earth.

Gravity is caused by mass, it holds us down to the surface which stops us falling in to space. Lol.

It is not known. We know how it behaves and can describe it very accurately. But it is not know how mass or energy bend space. Bent space is just a different way of saying gravity. It isn't an explanation.

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http://www.ehow.com/info_8579888_causes-gravity-ea...

its core