Identifying and explaining the
regularities of nature is the goal of science. Physics, like other sciences, is concerned with the regularities exhibited by particular systems. Stars, atoms, fluid flows, high temperature superconductors, black holes, and the elementary particles are just some of the many examples. Studies of these specific
systems define the various subfields of
Physics — astrophysics, atomic physics, fluid mechanics, and so forth. But beyond the regularities exhibited by specific systems, physics has a special
charge. This is to find the
laws that govern the regularities that are exhibited by all physical systems. The equality of gravitational accelerations of different things is an example. These are usually called the fundamental laws of physics. Taken together they are called informally a “theory of everything”. Stephen Hawking has been a leader in the quest for these universal laws. Today, I would like to ask the question: “How much do we know about the world if we have a theory of everything?” Ideas for the nature of the fundamental laws have changed as experiment and observation have revealed new realms of phenomena and reached new levels of precision. There is another way in which our vision of the fundamental laws and the nature of a theory of everything has changed since the times of Newton and Laplace. That is
quantum mechanics. We don’t yet know the final form the fundamental laws will take. But the inference is inescapable from the physics of the last seventy-five years that they will conform to that subtle framework
of prediction we call quantum mechanics. When we consider the universe as a quantum mechanical system, this initial condition is Hawking’s wave function of the universe. Probabilities are the key difference between classical and quantum mechanics.
More abstracts about the Theories of Everything and Hawking’s Wave Function of the Universe