Back to the Universe

A bargain even in 2001: 2 Hawking books plus pictures at a cost of $9.99.

Pi is an irrational number (3.14159265.... goes on forever to the right of the decimal point without repeating a sequence), and it's somehow fitting that one of the leading examples of human rationality, physicist Stephen Hawking, died on "Pi Day" (3.14) in England.

I took a crack at his best-seller, A Brief History of Time, when it first came out in 1988 but didn't have the discipline to read it (skimming a technical text is not considered reading, by the way). I had better luck in 2001 when it was reissued with pictures and diagrams. Here is an excerpt from the chapter entitled The Arrow of Time:

In a quantum theory of gravity, as we saw in the last chapter, in order to specify the state of the universe one would still have to say how the possible histories of the universe would behave at the boundary of space-time in the past. One could avoid this difficulty of having to describe what we do not and cannot know only if the histories satisfy the no boundary condition: they are finite in extent but have no boundaries, edges, or singularities. In that case, the beginning of time would be a regular, smooth point of space-time and the universe would have begun its expansion in a very smooth and ordered state. It could not have been completely uniform, because that would violate the uncertainty principle of quantum theory. There had to be small fluctuations in the density and velocities of particles. The no boundary condition, however, implied that these fluctuations were as small as they could be, consistent with the uncertainty principle.

The universe would have started off with a period of exponential or "inflationary" expansion in which it would have increased its size by a very large factor. During this expansion, the density fluctuations would have remained small at first, but later would have started to grow. Regions in which the density was slightly higher than average would have had their expansion slowed down by the gravitational attraction of the extra mass. Eventually, such regions would stop expanding and collapse to form galaxies, stars, and beings like us. The universe would have started in a smooth and ordered state, and would become lumpy and disordered as time went on. This would explain the existence of the thermodynamic arrow of time.

The above passage may be somewhat abstruse, but by the time the reader encounters it on page 191 Professor Hawking has already discussed thermodynamics, space-time, quantum mechanics, gravity, and the origin of the universe, all prerequisites to this discussion. He was a brilliant theoretician, writer, and teacher. R.I.P.

Time:

“Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist,” Hawking said of the meaning of life. “Be curious. And however difficult life may seem, there is always something you can do and succeed at.”