Fantasy or Reality - Does Star Trek Add Up?

THE PHYSICS OF STAR TREK

By Lawrence M. Krauss

Basic Books

188 pp., $18.50

As the family gathers for its Saturday-evening appointment with Capt. Jean-Luc Picard and the crew of the Federation starship Enterprise, a new Romulan cloaking device has left Geordi La Forge, Ro Laren, and a Romulan villain invisible, inaudible (to all but each other), and able to pass through matter.

The hero and heroine discover a Romulan plot to destroy the Enterprise, and they try to warn their colleagues. In the final scene, La Forge chases the Romulan, who chases a fleeing Ro, through walls, two people dining in 10 Forward, and a couple in an amorous embrace in a corridor. The villain meets his doom when a shove from La Forge sends him stumbling through the starship's hull and out into space.

As the credits roll, the family's nine-year-old daughter blurts out: ''Yeah, right! How come they didn't fall through the floor?''

You don't need a PhD in physics to be a cosmic killjoy. Science fiction can abuse science fact in obvious ways. The PhD comes in handy, however, in going beyond the obvious to ask: Are any of the technologies in Star Trek possible? What do the laws of physics allow and what do they rule out?

Lawrence Krauss, an astrophysicist at Case Western Reserve University in Cleveland, applies these questions to the popular TV and movie series to take readers of ''The Physics of Star Trek'' on an engaging tour of modern physics, genetics, and cosmology. In the process he opens some tantalizing technological doors, while slamming others shut.

Warp drive? He gives it a resounding maybe - in principle. General relativity allows for the possibility of ''warping'' the cosmic fabric of space-time so that it expands behind you and contracts in front. In theory, light-years could be traversed in minutes. In practice? The process would require a gravitational field as large as a starship-sized black hole. And the energy needed to make such a black hole would exceed the total energy output of the sun during its lifetime.

Transporters? He remains ''agnostic.'' While he says the data-processing needs conceivably could be met by the 23rd century, when the show is supposed to take place, other hurdles are formidable. One is raised by quantum mechanics and its uncertainty principle. ''It is ... impos- sible to resolve atoms and their energy configurations with the accuracy necessary to re-create exactly a human pattern,'' he writes. Another is raised by sensing techniques that would be needed to distinguish individual atoms 40,000 kilometers away (the transporter's maximum range).

After all, if you beam people to a planet, they have to return somehow. A fairly brief encounter between chalk and blackboard suggests that if the starship's sensors were scanning at X-ray or gamma-ray wavelengths - a must if you're looking for atom-sized material - its ''lens'' would have to be at least 50,000 kilometers in diameter.

Phasers? He's silent on this one, perhaps because they exist, according to an article in the current issue of The Sciences, a magazine published by the New York Academy of Sciences. The article reports that a phaser has been developed at Texas A&M University. Its potential end-uses - in high-resolution microscopes, for example - are a bit less apocalyptic than on Star Trek, however.

Krauss writes clearly and with an appreciation for series writer Gene Roddenberry's legacy: ''While it is an unfortunate modern misconception that science is somehow divorced from culture, it is, in fact, a vital part of what makes up our civilization.... By emphasizing the potential role of science in the development of the human species, Star Trek whimsically displays the powerful connection between science and culture.''

Like any good Trekkie, he leaves the transporter room open for a sequel. The name's already picked - Star Trek II: The Wrath of Krauss.