Fickle Universe

Younger by half? Maybe

How old is the universe? The question has perplexed scientists, to say nothing of theologians, at least since the 17th century, when an Irish divine, James Ussher, used the Bible to calculate the world's birth date as 4004 B.C. Since then, astronomers contemplating far-off stars and galaxies through powerful telescopes have steadily increased Ussher's figure. Today many scientists agree the universe goes back as far as 20 billion years, when it was created by an explosion irreverently referred to as the Big Bang.

Last week a team of astronomers, led by Marc Aaronson of the University of Arizona's Steward Observatory, detonated something of a minibang. Using new data obtained by observing the movements of a family of galaxies in the vicinity of the Virgo cluster, they assigned a new age to the universe. The universe, it now seems, is closer to 10 billion years old.

The controversial recalculation represents only the latest adjustment of a cosmological value known as the Hubble constant, after the noted astronomer Edwin Hubble. In the late 1920s, using the 100-in. Mount Wilson telescope, then the world's largest, Hubble discovered that everywhere he looked in the heavens, the galaxies seemed to be moving away from each other, like flecks on the surface of an expanding balloon, their speed increasing in direct proportion to their distance. By assuming the universe was expanding, astronomers used that ratio to reckon the universe's age and size. Trouble was that the Hubble constant proved notably fickle, as succeeding generations kept measuring the distance of different celestial bodies and getting different results. Admits Allan Sandage, who is using the new 100-in. Du Pont telescope at Las Campanas, Chile, to make his own measurements of the constant: "Everyone in this game is in disagreement."

Sandage prefers to stick with measurements implying an age closer to 20 billion years. Why? He cites, among other items, his latest research into the age of great spherical clusters of stars in the halo of the Milky Way. He and Colleague Gustav Tammann found they are some 17 billion years old. Asks Sandage, with the laconic understatement of a debater who feels sure he has found the clinching argument: "Isn't it rather hard to have a universe younger than its oldest components?"

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