Since the ancient Greeks first speculated that everything they observed in reality was the result of the interaction of tiny particles they called atoms, great thinkers have tried to find a single mathematical formula that governs and explains the workings of the entire universe.
So far, though, even minds as brilliant as physicists Albert Einstein and Stephen Hawking have been unable to come up with that single grand equation of everything, also known as the theory of everything, or the final theory. Nevertheless, they continue to try, because without that final piece of the puzzle that is reality, the sum total of what we know falls a bit short of making sense.
Perhaps the most illustrious searcher for the equation of everything was physicist Albert Einstein, who spent the last 35 years of his life trying to uncover such an overarching explanation. Einstein's own theory of general relativity, published in 1916, explained gravity, one of the strong forces in the universe, as the bending of space-time by matter. But general relativity didn't explain electromagnetism, another strong force that was even more powerful than gravity.
Einstein wasn't willing to accept that these two forces were unrelated, and he searched for a single explanation - a unified field theory - that would show how electromagnetism, gravity and space-time interacted. I see in nature a magnificent structure that must fill a thinking person with a feeling of humility, he once explained. But although he published a number of papers on his ideas about unified field theory, he died in 1955 without solving the problem to the satisfaction of other theoreticians. List of all episodes here: Through The Wormhole.