Why is gravity a force?
We assume gravity is a force. The thinking is mass distorts space-time so objects trapped within the the influence have a tendency to go to the centre of gravity. The earth produces a distortion with gravitation centre being the centre of the earth. The Sun and the great attractor at the centre Milk Way also produce similar space-time distortions. This is why the earth revolves around sun and the sun in turn revolves around the great attractor at the centre of the Milky Way.
Gravity is not a force. It is mathematically convenient to treat it as a force – in fact many orbital calculations are performed using that assumption. But when you are in free fall, you are accelerating toward the center of the nearest massive object, but there is no force acting on you. You cannot feel any reactions, your head is not thrown back, you feel nothing pushing against you, etc. Free fall is an acceleration that is produced without using a force. It is entirely caused by the warping of spacetime due to the mass of the central object. ADDED: The only force that occurs is the force required to oppose gravity. For example, a rocket may fire its engines in order to pull away from – or simply stand still next to – a gravity well. Or you may stand on the surface of the earth, causing a force to be applied to the soles of your feet. Einstein understood (his happiest thought) that you cannot tell the difference between these scenarios – because there is no difference. That is known
