The Theory of Everything: The Origin and Fate of the Universe

The Theory of Everything: The Origin and Fate of the Universe

By Hawking, Stephen

INTRODUCTION

In this series of lectures I shall try to give an outline of what we think is thehistory of the universe from the big bang to black holes. In the first lectureI shall briefly review past ideas about the universe and how we got to ourpresent picture. One might call this the history of the history of the universe.

In the second lecture I shall describe how both Newton’s and Einstein’s the-ories of gravity led to the conclusion that the universe could not be static; ithad to be either expanding or contracting. This, in turn, implied that theremust have been a time between ten and twenty billion years ago when thedensity of the universe was infinite. This is called the big bang. It would havebeen the beginning of the universe.

In the third lecture I shall talk about black holes. These are formed when amassive star or an even larger body collapses in on itself under its owngravitational pull. According to Einstein’s general theory of relativity, anyonefoolish enough to fall into a black hole will be lost forever. They will not beable to come out of the black hole again. Instead, history, as far as they areconcerned, will come to a sticky end at a singularity. However, generalrelativity is a classical theory-that is, it doesn’t take into account theuncertainty principle of quantum mechanics.

In the fourth lecture I shall describe how quantum mechanics allows energy toleak out of black holes. Black holes aren’t as black as they are painted.In the fifth lecture I shall apply quantum mechanical ideas to the big bang andthe origin of the universe. This leads to the idea that space-time may be finitein extent but without boundary or edge. It would be like the surface of theEarth but with two more dimensions.In the sixth lecture I shall show how this new boundary proposal could explainwhy the past is so different from the future, even though the laws of physics aretime symmetric.

Finally, in the seventh lecture I shall describe how we are trying to find aunified theory that will include quantum mechanics, gravity, and all the otherinteractions of physics. If we achieve this, we shall really understand theuniverse and our position in it.