Edition: U.S. / Global

Prediscovery Channel

By Jon Turney
Published: September 29, 2002


Undiscovered Ideas at the Frontiers

of Space and Time.

By Tom Siegfried.


307 pp. Washington:

Joseph Henry Press. $24.95.

If you thought physics was weird in the 20th century, wait until you read about the ideas coming your way in the 21st. Most of us still find notions like Einstein's relativistic reframing of space and time, quantum uncertainty or entities that behave like both waves and particles counterintuitive. But physicists and cosmologists are going boldly down paths lighted by ever more exotic mathematics. These take them farther and farther from everyday reality into underlying realms that are . . . well, exactly what they are is what Tom Siegfried wants to find out.

In ''Strange Matters,'' a fascinating but flawed book, he describes a host of aspects of the way things are that have this in common: at least some physicists think they fall out of their favorite equations. They range from mirror worlds and alternate universes to new families of particles, new forces, multiple hidden dimensions of space and even an extra dimension of time. All could be true, but in most cases we have little idea whether they are; we know only that they are not excluded by what is already known. They add up to, in his own phrase about work on just one idea -- supersymmetry -- numerous surmises about things the world might possess.''

They arise, as far as I can see, for three main reasons. For all its successes, modern physics still faces some intractable problems: how to combine relativity theory's account of gravity with quantum mechanics, for example, or why a whole raft of parameters in the so-called standard model of particle physics take the values they do. At the same time, the success of past departures from classical ways of seeing things gives endless license for speculation. Once you accept that gravity is due to the curvature of space-time, or that the quantum vacuum is seething with virtual particles, almost anything might be plausible, it seems. Finally, theoretical physics has become a refined form of creative play, in which testing out wacky ideas mathematically continually outruns experiment. Sometimes it outruns experiment so far the ideas are barely testable even in principle, but that doesn't stop it being enormous fun for those intellectually equipped to play the game.

Siegfried mostly makes it fun for spectators, too. As he emphasizes by interweaving historical sketches with his tales of current work, there are plenty of past examples in which mathematical ideas pointed toward unsuspected aspects of the universe. Just as Paul Dirac in the last century prompted discovery of anti-particles by pointing out that both the positive and the negative square roots in a particular equation might have physical correlates, perhaps today's artists of mathematics will reveal unseen entities.

Popular physics and cosmology is a crowded market, with many scientists having their own say in trade books; Lawrence Krauss, Martin Rees, Lee Smolin, Brian Greene and Janna Levin have all dealt with some of the ideas Siegfried tackles here. But his breezy treatment is a welcome addition to efforts to give access to the latest developments in fields that are hard for outsiders to keep track of. He finds words for concepts that are basically unvisualizable as well as anyone does -- although, when the analogies fall away, you still come up against statements like ''If the coupling strength is high, the Heterotic-E superstring looks more like a supermembrane requiring another dimension of space to vibrate in,'' the meaning of which is stubbornly elusive. The episodic structure of the book and the range of work it covers mean the treatment is scattered, not systematic; we do not get a clear explanation of special relativity until Page 240, for instance. But the impression this leaves of a welter of speculation, and enough loose ends left dangling to weave a whole new rug, is a fair reflection of the field.

Now, what of the flaw? Siegfried is an exceptionally knowledgeable guide, a science reporter who is on easy terms with all the leading players in physics, goes to their conferences and reads the journals. The picture he pieces together of a group of people stretching their imaginations to the limit to come up with ideas about how the universe might be built is persuasive. It comes, though, with an irksome extra. This is the rather bemusing notion that theorists are engaged in ''prediscovery.'' So if a physicist suggests that some system of equations indicates the possible existence of a new particle, a particular manifestation of a force or an unsuspected quirk of space-time, and his suspicion turns out to be well founded, he makes a prediscovery.

Why this new term is a better way of putting it than the more familiar, if still oversimplified, scheme in which theorists make predictions that are tested against observation once someone thinks up a sufficiently ingenious experiment is never quite explained. It certainly gets Siegfried into some strange philosophical tangles. He writes, for instance, of the fabled Higgs boson, needed to set the seal on the standard model of forces and particles, as a ''potential prediscovery'' that most physicists hope will happen. So the fact that the Higgs particle remains undetected seems here to mean that prediscoveries can be identified only retrospectively. But if the term means anything, surely the prediscovery of the Higgs has already happened? Prediscovery also makes it hard to describe observations that no previous theoretical speculation accounts for -- such as the universe appearing to contain far more mass than is visible to astronomers. Ironically, this stimulus to theories that would explain copious amounts of ''cold dark matter'' turns into one of the book's major case studies.

You can sort of see how Siegfried got into this, puzzling over the old conundrum of how it is that mathematics seems to reveal deep aspects of physical reality so well. And while it is easy to suggest that, in general, objects and processes -- in a word, phenomena -- are discovered, while ideas are invented, it is also possible to make mathematical discoveries. His publisher, though, is obviously wary of all this, since the book's subtitle refers not to prediscoveries but to ''undiscovered ideas.'' Those do sound hard to write about. That Siegfried's notion leads to such nonsense suggests that a kindly editor ought to have taken him to one side and told him to ditch it. As it is, one can always translate his descriptions back into more conventional terms. But as prediscoveries recur throughout the book, it feels a bit like trying to follow do-it-yourself instructions marked in meters when you only have an inch rule -- doable, but a tad irritating.