When a plane accelerates, the back of the seat pushes passengers to keep up with the plane, but parachutists in free-fall accelerate without feeling a force at all. A parachutist jumping from a plane feels no force when gravity accelerates them to the earth, so:
“It’s not the fall that kills you; it’s the sudden stop at the end.” Douglas Adams
But how can matter go faster when nothing is pushing it? Einstein’s insight was that a free-fall acceleration equates to being at rest, so gravity isn’t a force at all but the earth curving space and time around it, which he said was “the happiest thought of my life!” First he noted that the effect of gravity equates to an acceleration so in a rocket accelerating at 1g, people feel a force pulling on them just like gravity on earth. For example, they can sit down and have a cup of tea just as they do on earth. Gravity is indistinguishable from acceleration, except that no particles make it happen.
Einstein then showed that gravity occurs when the earth warps the time and space around it. This replaced Newton’s inexplicable force-at-a-distance by a gravity that equally inexplicably distorts space and time. For Newton, space was a fixed stage where objects acted in common time but for Einstein, gravity changes the space and time of that stage. A particle moving in a straight line then curves under gravity as if influenced by a force, but actually it is space that curves.
Gravity then is caused by changes in space and time, so the standard model claim that gravitons cause gravity denies general relativity, just as its claim that particles move on fixed paths denies quantum theory. Why then does current physics believe what contradicts its two best theories?
Relativity also explains Galileo’s earlier finding that but for friction, all masses fall at the same speed. A heavy object has more inertia so it should be harder to move, but for some reason the gravity on it is equally greater, so the effects cancel. A ton of lead hits the ground at the same time as a feather because according to relativity, gravity varies with mass just as inertia does. It was a brilliant solution, but it left the standard model with a force that none of its particles could explain.