Search for a Supertheory: From Atoms to Superstrings by Barry Parker (Plenum: $21.95; 292 pages, illustrated).
What is the world made of? is a question that people have wondered about since the ancient Greeks. But only in this century has science zeroed in on the right answer, which turns out to be extraordinarily elusive.
Theoretical physics is not easy. In fact, it's very hard. So a book that sets out to trace the development of theoretical physics in the 20th Century is going to be one tough cookie. "Search for a Supertheory" is exactly that.
Barry Parker, a physicist at Idaho State University and sometime science writer, takes a crack at telling the whole story as lucidly as possible.
The result is a hodgepodge of particles that is aesthetically unappealing but mathematically sound. It enables theoretical physicists to make predictions that experimental physicists verify in their giant atom smashers, but few people are happy with the resulting theory.
Physics rests on the belief (yes, the belief ) that the universe is both knowable and simple. Knowable it may be, but so far, simple it is not. Parker puts the current situation this way:
"The real difficulty is the theory itself. Within it are 18 colored quarks and six leptons; furthermore, 12 exchange particles are needed to account for the interactions between them. We originally introduced quarks because the number of 'elementary particles' was getting out of hand. And the three quarks that were introduced were certainly an improvement over the hundreds of 'elementary particles' that were known at the time. But now it appears that things are getting out of hand again."
In recent years, physicists trying to get a grasp on the basic structure of matter have come up with what is called superstring theory, which makes possible the unification of many ideas and observations but leads to certain problems of its own, among which is the notion that the universe contains not three, not four but 10 dimensions, six of which are invisible. The mathematics works well enough, but no one has a clue what this could possibly mean.
Parker writes: "For a theory to be a 'good' theory it has to predict things that are observed, or that might be checked. Can superstring theory predict anything that we can check? So far it hasn't."
Nonetheless, many physicists, particularly the younger generation, believe that superstrings are the Theory of Everything and will prove to be the Holy Grail that physics has been seeking. Perhaps they are right.
But as one reads again of the development of theoretical physics in this century, it is hard not to think of Ptolemy, the 2nd Century Greek astronomer, who thought the Earth was in the center of the universe and had to keep inventing more and more complications in the orbits of the planets to make his theory square with observations of planetary motion.
Eventually it took Copernicus to straighten things out and simplify them by realizing that the sun is in the center of the solar system and all of the planets, including the Earth, revolve around it.
It is hard not to think that theoretical physics today is like the Ptolemaic universe, full of structures invented to make things come out right but nonetheless wrong. Will a second Copernicus appear someday to show that physicists have been barking up the wrong tree all this time and that matter is much simpler than they had thought?
At the same time, there is no guarantee that the universe is ultimately simple. Kepler, who followed Copernicus and discovered that the orbits of the planets are actually ellipses, not circles, around the sun, also believed that the universe was simple. This belief led him to make several mistakes.
In Kepler's time, only five planets were known. Following his belief in simplicity, Kepler believed that the five planets corresponded to the five regular solids that were known by Euclid and that each planet's orbit was inscribed in one of those regular solids.
This view was completely wrong. In fact, there are not five planets in our solar system but at least nine, and their orbits have nothing to do with Euclid's regular solids. So much for Kepler's simple, beautiful theory.
Is the universe simple? We don't know. Is there one Theory of Everything that will unify all of the particles and forces that physicists have discovered? We don't know. Is there a simple way to explain all of what is now known and how we know it? Not yet.
Parker has tried to put it all together, but he has written a book that will appeal more to physicists than to general readers. It's not altogether Parker's fault. There may be no way to make all of this accessible to nonspecialists.