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Anthony: but can you prove it and how?
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What the above people are describing is gravity according to Einstein's general theory of relativity. General relativity has been confirmed by several observations.
Because the Sun is massive, it should warp the spacetime surrounding it. Thus, light that passes by the Sun should be deflected from a straight line course; it should follow the straightest possible path in the curved spacetime. In short, a star that appears to be next to the Sun should have its light bent during its travel past the Sun. To test this, some such stars were observed during a eclipse and their positions were found to be slightly off of where they should have been - their light had been bent by the Sun's mass. Since then other such observations have confirmed the bending of light by mass: one has even come to be known as Einstein's Cross - it is a single star (or is it a galaxy?) that appears to be multiple positions at once, forming a cross-like shape.
Another has to do with orbital precession. Mercury's orbit had been known to have a very slight deviation from that predicted by Newton's theory of universal gravitation. That is, the ellipse of Mercury's orbit slowly moved around the Sun. Einstein's general relativity described Mercury's orbital precession quite nicely whereas Newton's didn't.
Einstein also stated that strong gravitational fields - large curvatures of spacetime due to mass - would cause time dilation, and this too has been experimentally confirmed.
Another prediction of Einstein's general relativity is that gravitational waves exist and that they travel at the speed of light. I know that experiments were planned to detect gravitational waves, but I stopped keeping track of that kind of thing a couple of years ago. If the experiments have been carried out, then they would add to the pile of evidence that confirms Einstein's view of gravity as being warped spacetime.
