In his book "Einstein: His Life and His Universe," Walter Isaacson explains Newton's law of universal gravitation. It states that every two objects in the universe attract each other through a force that depends on their masses and the distance between them. The attraction increases with the mass of the objects and decreases as the distance increases.

This fundamental principle laid the groundwork for understanding gravitational interactions, influencing later theories of relativity. Newton's insights into gravitational forces significantly advanced the field of physics and shaped our understanding of celestial movements and various phenomena in the universe.