The importance of Albert Einstein’s unified field theory
Albert Einstein struggled to find a method to unite the basic forces of nature into a single theory. He spent a great deal of time and energy trying to reconcile gravity with the other forces. Ultimately, he admitted failure. Three of the basic forces, electromagnetic, strong nuclear, and weak nuclear, have been combined into what appears to have been a single force in the very early times of the universe.
Gravity is very different from the other three, though, and thus far no single theory has managed to enfold gravity with the other three in a way that can be defined mathematically and is acceptable to physicists. Most attempts to write an equation that covers all four forces have been discarded, either the math is too tangled to sort out or because the equation ends up with multiple infinities.
A large part of Einstein’s difficulty with creating a unified field theory was the trouble he had with quantum mechanics. His famous statement was “God does not play dice with the universe.” Both theoretical and experimental physicists have demonstrated clearly, however, that whether it is “God” or just the functioning of natural law, the universe does indeed play dice, at least at the quantum level.
Another difficulty Einstein had with quantum mechanics was the prediction by quantum theory that measuring something in one place could affect something else in another place instantaneously. In the thought experiment proposed by Einstein, Podolsky, and Rosen (known as the EPR experiment) he used the structure and results of that experiment to claim that because it would require what Einstein later called “spooky action at a distance”, quantum mechanics must be incorrect. It is spooky and it is difficult to comprehend. Nonetheless, all subsequent experiments have demonstrated that the predictions of quantum mechanics are correct. Look up Bell’s Theorem for a clear discussion and solution to the EPR paradox.
Modern physicists have concocted a variety of theories to try to unify the laws of nature. There have been strings, superstrings, M-branes, multi-universes, and some other even more exotic proposals. None of them cleanly and accurately solve the problem, possibly because the math is too difficult.
Einstein’s theory of relativity has withstood the test of time and has been verified in its predictions by a multitude of experiments. It is, however, a classical theory in the sense that it builds on the theories of Newton rather than replacing them. He could not fully grasp the quantum world and incorporate it into his theory.