The Infinite Universe

Most contemporary cosmologists agree that the universe was created billions of years ago when a superdense clump of primordial matter exploded with incredible force. The hot gases created by the "big bang" were flung violently outward, gradually cooling and coalescing into great islands of stars, or galaxies, that are still moving away from one another. Last week, after years of study and calculation, two respected California astronomers, Allan Sandage and James Gunn, made separate but similar announcements: the universe will continue to expand forever.

That conclusion will be disturbing to those who find the concept of an infinitely expanding or "open" universe to be philosophically unsatisfactory. "Closed universe" scientists have long contended that if there was enough matter in or between the galaxies, there would be enough mutual gravitational attraction to gradually slow their outward flight. The expansion would halt, and all the parts of the universe would begin to fall inward, eventually crushing together again in a final cataclysm. Some closed universe theorists hold out the possibility that matter would in effect rebound from the crunch in another big bang and that the universe would continue to oscillate, expanding and contracting forever. Now both theories seem to be seriously undermined.

Sandage, of the Hale Observatories, bases his conclusion on 15 years of pains taking observations of distant galaxies and measurement of the amount that their light is shifted toward the red (or lower frequency) end of the spectrum. Just as the pitch (or frequency) of a siren appears to lower as it moves away from an observer, so the light from a galaxy is shifted toward the red by an amount proportional to the speed at which the galaxy is moving away from earth. Also, because of the general expansion of the universe, the velocity at which galaxies recede from the earth increases with their distance from it. Thus astronomers can determine a galaxy's distance by measuring its red shift. Sandage, working with Swiss Astronomer Gustav Tammann, used Mount Palomar's 200-in. telescope to measure the distances of nearby galaxies and compare them with the corresponding red shifts.

That enabled him to calibrate the relationship between distance and red shift much more accurately than ever before.

Using his new yardstick, he concluded that all galaxies were more distant than astronomers had previously believed. That, in turn, meant the expansion had been going on longer than anyone thought, and that the age of the universe was at least 16 billion years, or roughly 4 billion to 6 billion years older than earlier estimates. Even more important, the redshift measurements of nearby galaxies gave no indication of any significant gravitational slowdown in the outward rush of the galaxies. "It's a terrible surprise," says Sandage, who for years had been leading proponent of the idea that the universe would eventually close in on itself.

Gunn, a Caltech astronomer, made no direct observations. In collaboration with three associates, he spent six years studying a wide variety of evidence--including Sandage's redshift measurements. For one thing, he examined the galaxies' brightness and movement, which offer clues to their mass. He also estimated the probable incidence of "black holes," small but extremely massive bodies that are invisible to astronomers. From these and other clues, Gunn's group concluded that the universe has no more than a tenth of the mass--and probably less --needed to close it. "Pulling all the arguments together," says Gunn, "an open universe wins by a wide margin."

Both men expect their conclusions to stir a storm of protest from some of their colleagues. For, as Gunn puts it, the arguments for a closed universe are almost "theological in nature." Indeed, Gunn finds the implications of an open universe thoroughly mind-boggling and paradoxical. "Even though the density of its mass is small," he explains, "the total amount of mass is infinite because space is infinitely big." Sandage agrees. "This expansion is such a strange conclusion," he says. "One's first assumption is that it cannot really be true, and yet it is the premier fact."

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