Gravitational Field and Gravitational Potential

Two masses like the Sun and the Earth are never in physical contact with each other, and yet the Earth clearly experiences a huge, continuous pull toward the Sun. Contact forces (like a push or a pull you apply with your hand) are easy to picture and measure directly, because you can feel or see the two objects touching. But how do you even calculate the strength of a force that acts at a distance, with nothing physically connecting the two objects? …