The Science Behind Final Theory
The Quantum World
The pioneers of quantum mechanics — Niels Bohr, Erwin Schrodinger, Werner Heisenberg and others — proposed a logical extension of Einstein's ideas: if a light wave could act like a particle, then perhaps a particle such as an electron could act like a wave. Researchers had previously viewed the electron as a tiny speck that buzzes madly around the nucleus of an atom, but in the quantum view an electron is actually a "probability cloud," a wavelike smear surrounding the nucleus. Quantum mechanics turned out to be an amazingly successful theory that explained all sorts of subatomic phenomena and even predicted the existence of new particles that weren't discovered until many years later (such as the antiproton and the neutrino).
But unlike a classical theory such as relativity, quantum mechanics has inherent uncertainties. The quantum wave-function equations don't specify the exact position of a particle but only provide a distribution of probabilities indicating where it might be. What's more, Heisenberg's uncertainty principle states that even the most precise instruments can't simultaneously determine the exact position and momentum of a particle; complete, perfect knowledge of the system is unattainable. In short, the quantum world isn't deterministic. Fundamental particles apparently don't follow the classical rules of cause-and-effect that apply to larger objects such as billiard balls or planets. When particles interact, you can't predict exactly where they'll end up.
Einstein found this situation unacceptable. He refused to believe that even a subatomic smidgeon of the universe could be unpredictable or unknowable. As he stated many times:
“God does not play dice with the universe.”
Einstein became convinced that quantum mechanics was provisional and that it would be superseded by a more comprehensive, classical theory — the Einheitliche Feldtheorie, or unified field theory. Such a theory would explain both gravity and quantum mechanics, and predict the masses of all the fundamental particles as well. The key to formulating the unified theory, Einstein believed, was finding the "hidden variables" that control the subatomic workings of the universe. Once the hidden variables were identified, all the quantum uncertainties would vanish. The search for the unified theory obsessed Einstein from the 1920s to the 1950s. In some of his attempts to solve the problem, he posited the existence of an extra dimension, a hidden fifth dimension that would complement the three familiar spatial dimensions (length, width and depth) and the dimension of time. In other attempts, Einstein investigated alternative spacetime geometries. But all of his published solutions proved to be flawed, and after Einstein's death in 1955 the quest for the Theory of Everything was largely abandoned — until the 1970s.