General Relativity Vs Quantum Mechanics

A physicist’s job is to use humanity’s understanding of how matter and energy interact to learn about the Universe. The job of physics, however, is to unite the four fundamental forces of nature: Gravity, Strong and Weak Nuclear, and electromagnetism, into a single physical model; A theory of everything. In the 20th century, physicists revolutionized humanity’s understanding of these forces and made great strides in uniting them, but the two theories which have brought humanity the closest to this unified field theory, the theories of general Relativity, and Quantum Mechanics, cannot seem to coexist. Both of these theories have made immense contributions to science, but unless physicists can find a way to unite these two scientific principles

It’s not a very profound thought but it's true, and since our best theory of gravity is Einstein's theory of general relativity, The most obvious thing to do is just apply that theory to the subatomic realm. As an illustrative example, let's imagine an electron orbiting a nucleus. If you do that you find that Einstein’s theory predicts that the electron would lose energy by the emission of gravity waves and then spiral down into the proton. A similar prediction using classical electromagnetism led to the invention of quantum mechanics. This same chain of reasoning suggests that gravity must also have some kind of quantum nature (Lincoln).

Obviously if atoms functioned as proposed by general relativity, matter would fail to exist in the universe. If scaling relativity down fails to make sense, applying quantum mechanical theory on a relativistic scale would be a logic next step. Physicists quickly found that quantum field theory fails to account for the warping of spacetime proposed and observed by general relativity. Paul Stutter, an Astrophysicist and journalist for Space.com summarizes the complexities of these factors

Uncovering the nature of how gravity works on the quantum level is the key to solving the theory of everything, and by taking a closer look at both quantum mechanics and relativity, physicists hope to unite the four fundamental forces of nature. In an attempt to merge the two greatest scientific theories of the twentieth century, physicists have hurled themselves down a rabbit hole through the fabric of space and time. From relativity and quantum mechanics to the geometry of greater dimensions, to superstring theory and quantum loop gravity, the search for quantum gravity has become more and more complex. A famous adage in science is whenever one question is answered, a hundred more appear. As scientists dig deeper in the pursuit of bringing general relativity and the laws of quantum mechanics together, thousands of new questions are sure to appear before the theory of everything can be brought into