if gravity is what holds mass together,what is the repulsive force that keeps them apart?

Question

why dont we crash into the sun?

Answer 1

So far there have been a couple of answers and they are all hitting pretty close to the mark, even if they sound a lot different from each other.

One answer approaches the question from the position of the bending of space by the presence of mass. That is what gravity really is, but it's not the easiest concept to grasp. For a beginner, the classical mechanics example is best.

Newton's laws of motion tell us that an object in motion wants to stay in motion in a straight line. That is Linear Momentum. That is what the earth wants to do.
The mass of the sun, however, bends space-time.
This is the classic example of putting a heavy object in the center of a trampoline or bed. It makes a dimple in the surface. If you roll a ball in what would normally be a straight line, the ball will be affected by the dimple and its path will deflect to one side as a result.
That is what the sun does. Its mass causes space to be curved, and that manifests itself as gravity.
So while the earth wants to keep going in a straight line, gravity bends that straight line into a curve. The pull of gravity is called "Centripetal Accelleration" The word "centripetal" means "center seeking". So what keeps the earth in its orbit is the balance between Linear Momentum and Centripetal Accelleration (gravity). It is NOT Angular Momentum. Angular Momentum is what keeps the earth rotating on its axis, not what makes it move through space.

If the forward velocity of the earth (momentum = mass x velocity when mass is constant) were to be reduced, then the earth would start spiraling into the sun. If the forward motion of the earth increased, it would start spiraling farther out into space.

Answer 2

OK

Try this on:

We are not orbiting the Sun (planets) what we are really doing is spiraling into the center of the Sun. However we will never reach it as we are shrinking in amplitude (the whole universe that is) and expanding out at the same time. Similar to a sound wave frequency. Like the mathematical equation 1/x. Moving out in all directions (expanding) but decreasing rapidly at the same time and all objects in the universe are doing this at the same rate!

Therefore from our vantage point (anywhere in the universe) we cannot observe this. So again, we are spiraling into the sun like all planets do, but will never reach it and remain in the appearance of an orbit.

Ah heck, I think this information is for another lifetime, who the heck am I telling this to anyway!

Answer 3

Hang onto the side of a roundabout that is spinning quite fast. Then you can feel your angular momentum trying to throw you off the ride. Gravity is equivalent to you holding onto the ride!

Answer 4

angular momentum. Think of it as centrifigal force (actually centripetal is the correct word, but you probably never heard of that).