Is gravity made of particles or waves?

Question

Anna Armstrong · Accepted Answer

Gravity can't be described in terms of either particles or waves.

Although it's a good approximation, Isaac Newton's description of gravity as an attractive force between masses left many unanswered questions, including how the force is propagated. We now know that the universe can be described in terms of four dimensional space time. Before the theory of relativity was developed, the universe was thought to be three dimensional space and time to be a steady flow from the past to the future. Gravity is explained by Albert Einstein's field equations. #G^(mu nu)=(8pi G)/c^4 T^(mu nu)# This apparently simple equation is actual ten second order partial differential equations which are very difficult to solve. The #T# term on the right hand side describes mass, energy and momentum. The #G# term on the left hand side describes how spacetime is curved by the presence of mass, energy and momentum. As the constant #G# is very small and #c# is large, it says it requires a lot of mass and energy to bend spacetime. Time slows down in curved spacetime, and gravity is the result. Therefore, gravity is not a force; rather, gravity is the result of curved spacetime. Gravitational waves, which have recently been detected, are predicted by general relativity as well. When two massive objects, like black holes, collide, spacetime is bent, causing very small waves to be sent through it.

Jordan Andrews · Answer

undefined The general theory of relativity defines gravity as the curvature of spacetime due to mass and energy, rather than being made up of particles or waves as is the case with particle theory.