When a plane accelerates, we feel the back of the seat pushing us to keep up with the plane, but parachutists in free-fall feel no force at all as 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 if there is no force, isn’t that being at rest? Einstein’s insight was that 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 called “the happiest thought of my life!”
If gravity is indistinguishable from acceleration, passengers in a rocket accelerating at 1g feel an effect like gravity, so can sit down and have a cup of tea as they do on earth. But isn’t acceleration supposed to be caused by particles? Not according to Einstein, who replaced Newton’s inexplicable force-at-a-distance by equally inexplicable distortions of space and time. He made the stage changeable no fixed, so gravity bends particles by changing space and time not by exerting a force.
He also explained Galileo’s finding that but for friction, all masses fall at the same speed. A heavy object has more inertia, so it is harder to move, but if gravity is equally greater, the effects cancel. A ton of lead hits the ground at the same time as a feather because gravity varies with mass as inertia does. It was a brilliant solution, but it left the standard model with a force that none of its particles could explain.
If gravity works by changing space and time, gravitons contradict general relativity, just as particles contradict quantum theory by taking fixed paths, but matter-based physics still accepts the standard model because it has no other option. Quantum realism however does.