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Newton's Law of Gravity


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Gravity & General Relativity

When Newton presented his theory of gravity, he had no mechanism for how the force worked. Objects drew each other across giant gulfs of empty space, which seemed to go against everything that scientists would expect. It would be over two centuries before a theoretical framework would adequately explain why Newton's theory actually worked.

In his Theory of General Relativity, Albert Einstein explained gravitation as the curvature of spacetime around any mass. Objects with greater mass caused greater curvature, and thus exhibited greater gravitational pull. This has been supported by research that has shown light actually curves around massive objects such as the sun, which would be predicted by the theory since space itself curves at that point and light will follow the simplest path through space. There's greater detail to the theory, but that's the major point.

Quantum Gravity

Current efforts in quantum physics are attempting to unify all of the fundamental forces of physics into one unified force which manifests in different ways. So far, gravity is proving the greatest hurdle to incoporate into the unified theory. Such a theory of quantum gravity would finally unify general relativity with quantum mechanics into a single, seamless and elegant view that all of nature functions under one fundamental type of particle interaction.

In the field of quantum gravity, it is theorized that there exists a virtual particle called a graviton that mediates the gravitational force, because that is how the other three fundamental forces operate (or one force, since they have been, essentially, unified together already). The graviton has not, however, been experimentally observed.

Applications of Gravity

This article has addressed the fundamental principles of gravity. Incorporating gravity into kinematics and mechanics calculations is pretty easy, once you understand how to interpret gravity on the surface of the Earth.

Newton's major goal was to explain planetary motion. As mentioned earlier, Johannes Kepler had devised three laws of planetary motion without the use of Newton's law of gravity. They are, it turns out, fully consistent and, in fact, one can prove all of Kepler's Laws by applying Newton's theory of universal gravitation.

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