Relatively speaking: Einstein was right

Monday Book Review

June 20, 1994|By Sallie Baliunas


IF Q can travel through time, why can't we? Q is the wise guy advanced intelligence in "Star Trek: The Next Generation." Q scoots through the mixture of time and space. And like Q, physicist Kip Thorne thinks that time travel is possible. His book is a delightful and well-written history of relativity that culminates in his notion of cosmic time machines.

Mr. Thorne and colleagues broke time travel into the science literature in 1988 as part of the legacy of Einstein's theory of relativity. (Other bizarre consequences of relativity are "black holes," "singularities" and "wormholes.") Mr. Thorne enthusiastically recounts how far we have traveled since Einstein published his theory beginning in 1905. Our sophisticated telescopes verify that critters like black holes exist, just as Einstein's theory predicted.

What is the idea of the black hole that pops out of Einstein's theory? Einstein said that gravity is merely bent spacetime. With enough of a warp in spacetime, gravity is so powerful that light cannot escape. Mr. Thorne takes us along the winding paths of the physicists who think about black holes and their consequences.

Where to look for a black hole? In the heart of a supernova. A star just a few times the mass of the sun will eventually explode and throw off its outer layers after it has consumed the nuclear fuel in its core. The core Mr. Thorne takes us along the winding paths of the physicists who think about black holes and their consequences.

implodes and collapses into a dense object. It's squeezed into a space roughly the size of downtown Baltimore, and a marble-size chunk of it will weigh as much as the Earth. The black hole will bend the space around it so much that its light doesn't reach us, and it can't be seen.

Now if the collapsing star is one of two stars formed together, the gas from the companion star may be dragged into the black hole. The gas accelerates and heats up as it nears the black hole. It swirls faster until it is gulped by the black hole. The hot, moving gas can be seen by our telescopes. Such an unusual circumstance may not be so rare -- most astronomers believe we are seeing a black hole's appetite in the star system Cygnus X-1, which emits powerful X-rays.

The tale of Einstein's legacy has many subplots, including the development of the H-bomb. Mr. Thorne's account of the well-known removal of H-bomb physicist J. Robert Oppenheimer's security clearance is timely because of the recent and highly controversial book by Pavel Sudoplatov, the Soviet spymaster. Mr. Sudoplatov claims that Oppenheimer had leaked bomb secrets.

Mr. Thorne has no new information about what is viewed by most physicists as a political tragedy, but he documents Oppenheimer's great contributions to the understanding of black holes. In 1939, Oppenheimer predicted that the collapse of a star into a black hole continues until all of the star's matter is at a single point, called a "singularity." And "wormholes" -- "tunnels" connecting great distances through the warps of spacetime -- may exist between two singularities. If wormholes allow "shortcuts" through space, they may also be time machines. Which brings us back to "Star Trek."

When Mr. Thorne's personal threads of spacetime weave into the quest for new physics, the result is anecdotes and insights told with great warmth. The author debuts as a graduate student at Princeton in 1962. We see the conversion of his mentor, John Wheeler, from non-believer to apostle of black holes, and we see Mr. Thorne's interaction with one of the cosmic forces of modern physics, Stephen Hawking, with whom he places many bets on the outcome of their research. In 1974, Mr. Hawking bet against Mr. Thorne that Cygnus X-1 would be a black hole, and Mr. Hawking has since conceded.

That Mr. Thorne is a gambler is only proper for a theoretical physicist. After all, the scientist starts with just a feeling, hoping that it will become a winning theory. Mr. Thorne's betting is the stuff of physics -- powerful beliefs that make theories that are to be challenged by the scientific method. And the pace of science can be quick. Since publication of the book, the Hubble Space Telescope has seen a gigantic black hole in the heart of a distant galaxy, M87. Mr. Thorne wins.

Sometimes the payoff of the physicist's gamble is big, as in Einstein's idea and its legacy. In the case of quantum gravity and its possibilities of wormholes and time machines, both Mr. Thorne and Q, the time traveler in "Star Trek," want us to grow up -- by becoming students, then masters, of spacetime. Mr. Thorne gives time travel odds so long that he won't even book the bet with Mr. Hawking (who thinks that time travel is forbidden, and that will "keep the world safe for historians.") Mr. Thorne speculates that with a better understanding of quantum gravity, we may be able to decide if time machines are possible. These bizarre concepts may let us cross the unimaginably great distances that separate us from our neighbors in the cosmos.

Sallie Baliunas is an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and deputy director of the Mount Wilson Observatory in California.

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