Do we know if gravity pushes or pulls?

Question

If I were to hold a baseball ten feet from the ground then release it. Is the baseball being pulled in toward the Earth or pushed toward the Earth? I expect everyone will tell me it's being pulled in. If this is the case, how certain are we of this and what evidence supports it?

Answer 1

There are three theories...

Newtonian which is the model we normally use, where the masses are treated as they act at their centroid. So, when you "drop" the baseball the baseball and the earth actually move in inverse proportion of their masses toward each other. So the earth indeed does close the distance to the baseball, by an infitismal distance. Since the baseball has as significantly lower mass, it does most of the movement.

Then there is Einstienian where the ball nor the earth pulls or pushes, but the ball is release to travel its curved path in space which intersects with the earth.

Finally there is the theory that there is no gravity, the earth sucks.

Answer 2

If you were to throw a baseball past a planet, depending on how close it got, it would either get drawn in by it, be slightly affected by it, or seem to not be affected at all by it.

If there were two planets of the exact same mass, and you threw the ball precisely in between them, the ball would continue on in a perfectly straight line.

EVERYTHING in the universe that has mass affects, and is affected by, the gravitational forces of everything else, but gravity (in theory) is simply a displacement of space/time. Envision a 10' x 10' flat sheet of rubber supported at its corners, and lay a bowling ball in the middle. Now roll a marble across the rubber. If the marble gets close enough to the bowling ball, it will roll towards it. This is believed to be how objects affect space/time. When you get far enough away from an object, it's displacement of space/time is first balanced, and then exceeded by the effects of all other objects in the universe. It seems as though the force of gravity "runs out" when you get far enough away, but it's really just that it's displacement of space/time is being exceeded by the masses of other objects.

If all objects had "pushing force" as you describe, those forces would have to begin at infinite points outside the universe and progressively increase as they approached each respective object. We know that the universe is expanding and that rate of expansion is increasing, therefore If there were countless universal external pushing forces, it seems unlikely that this could happen.

Your suggestion also seems to contradict gravity's affect on light, but that is a whole nother can of worms.

Answer 3

Certainly the bouncing back of ball have created a paradox in your mind and certainly your quesiton is valid.

Look, if the earth is pulling th ball back than the basketball wont cone to rest at all and it will continure to bounce up and down forever.

But as we see that the ball comes to rest after a certain period this proves that gravity has a negative (or against) effect on the bouncing of the basketball.

Answer 4

First we have to decide if there is such a thing as "pulling". If I pull a drawer open, I am actually pushing the inside of the handle with the part of my fingers that wrap around the back. A vacuum cleaner seems to pull, but in reality, a vacuum applies no force and nothing within a vacuum moves unless there is pressure to push it.

Answer 5

well, if it were being pushed from somewhere out there, we'd need to find the source of the pushing. since we've never encountered anything that seems to forcibly repel things towards a planet, but all planets and large masses seem to attract things inward toward them, it stands to reason that gravity pulls inward. unless theres something out there in space that just happens to push things towards planets but only when they're close to them already. that seems incredibly unlikey, as theres not many things that close to them to start with.

Answer 6

It has been long held that the earth pulls smaller masses toward its larger mass. Is there something else like subatomic matter pushing smaller masses towards larger masses, like a flowing stream of subatomic particles acting on matter, If they detect subatomic black holes within atoms then this will throw how we view gravity on its head.

Answer 7

pull. The ball is essentially seeking the center of the earth

Answer 8

We know it pulls because of the moons effect on the oceans.
The water is attracted by the moon and thus we have tides.

Also you can take 2 large masses and suspend them near each other and measure the slight deflection in the cable suspending them. They attract each other.

Answer 9

Niether it follows its curved path through space!

Answer 10

pull

evidence? the apple that fell on newton