Re: Nerds and Bigger Bangs

Anthony, I won’t comment on the putative geekiness of Neil Turok , given that many people, including some of my own children, would aver that I am myself a geek of the first water. I can say, however, that Neil has always seemed to me, on the few occasions I have met him, a very nice fellow. And everyone would agree that he is an excellent physicist. But readers of First Things are doubtless more interested in Turok’s theories than in Turok himself. Given that in some of his theories the universe has no temporal beginning, should a Christian or Jew be worried?

There is a long history of attempts to construct viable theories in which the universe has no temporal beginning. One of the biggest obstacles to such attempts is the Second Law of Thermodynamics, which says that systems tend to run down. It is because of the Second Law that it is thought to be impossible to build a perpetual motion machine, and one could think of a universe that has been going on forever as a perpetual motion machine.

A long time ago, it was suggested that the Big Bang might have been just one “bounce” in an infinite sequence of bounces with no beginning or end. That is, in each cycle the universe expands, reaches a maximum extent, collapses to a point (or to a very small size), and then rebounds to begin a new phase of expansion. Back in the 1930s it was shown by the physicist Richard Tolman that such a sequence of bounces could not have been going on for infinite time. Due to the Second Law of Thermodynamics, the entropy of the universe would increase with every bounce, and Tolman showed that as a consequence each cycle would take longer than the previous ones. Thus, if the duration of our cycle were 100 billion years (to pick a round number), the previous cycle might have lasted for only ½ of that, the one before that only ¼ as long, and so on. Thus even if there were an infinite number of cycles before the present one, their combined duration would have been finite (since 1 + ½ + ¼ + etc. adds up to a finite number).

There have been many other eternal universe scenarios proposed over the years, some involving bounces, some involving universes spawning other universes in an infinite succession of generations, yet others involving what is called “eternal inflation.” The cyclic universe idea of Steinhardt and Turok is simply the latest attempt, and is itself an outgrowth of another scenario they proposed a few years ago that they called the “ekpyrotic universe.”

Such ideas are to be taken seriously. They may sound wild to the layman, but they don’t sound wild to most theoretical particle physicists or cosmologists. We already know things about the world that are far stranger than anything proposed in these scenarios. I personally would not be at all surprised if the Big Bang turned out not to be “the beginning”, though how we would ever be able to know that is hard to say. I would be quite surprised, however, if it turned out that the universe had an infinite age, i.e. that it truly had no temporal beginning, since it goes against the grain of everything modern science has learned about the universe. The Steinhardt-Turok idea has a very clever way of beating the Second Law of Thermodynamics; but Nature, if I may put it this way, is not mocked. The theorist may think he has outsmarted the Second Law or some other fundamental principle, but he usually ends up discovering that he has run up against it in another guise or run into some equally formidable obstacle.

For example, most theorists do not think the “eternal inflation” idea of Andrei Linde (which has far more going for it that the Steinhardt-Turok idea) can describe a universe that is eternal into the past, though it may describe one that is eternal into the future. (This conclusion is supported by theorems recently proved by the cosmologists Guth, Borde, and Vilenkin.) Similarly, serious technical objections have been raised to the “cyclic universe” idea of Steinhardt and Turok. Further work may show that these objections can be met, but at the moment, their idea should be regarded (and generally is by experts) as a very interesting, but extremely speculative and quite problematic scenario, and nothing more than that.

What the layman should know, and strive to remember when he reads some breathless article about the latest breakthrough, is that the world of fundamental physics is always frothing with speculative ideas, the more spectacular of which get fastened onto and hyped by the popular science media. Scientists are happy to abet this, since the hype gets them a lot of attention and, ultimately, funding. Everyone enjoys a good scientific revolution; no one more than I. And I don’t want to be a wet blanket; but when it comes to imminent breakthroughs that will radically change our view of the cosmos, in most cases it is sound and fury signifying very little.