for National Geographic News
It could be a time-honored philosophy of Eastern gurusthe view that time has neither a beginning nor an end, and that the universe is locked in a perpetual cycle of formation and dissipation. But it's the latest scientific model of the cosmos, and it comes from top theorists in Princeton, New Jersey, and Cambridge, England.
This new, cyclic model of the universe offers an appealing alternative to the prevailing theory, according to Paul J. Steinhardt, a theoretical physicist at Princeton University. "It predicts all the features of the standard model, using fewer ingredients," he said.
Steinhardt and his colleague Neil Turok of Cambridge University proposed the new model in a report posted April 25th on the Science Express Web site of the journal Science.
In the most widely accepted cosmological model, called the inflationary model, the universe was born in an instantaneous creation of matter and energy known as the Big Bang. As the universe has inflated since that event, matter and energy have spread out in clumps. The spreading could potentially continue forever.
"The inflation idea has been tremendously influential," noted Robert P. Kirshner, an astrophysicist at Harvard University. "No observation's been found that proves it wrong." But, he added, "that does not, of course, mean that it's right."
Nevertheless, the inflationary theory has survived since it was introduced in the late 1970s, while cosmologists have discarded competing ideas one by one.
New Theoretical Competition
Steinhardt was one of the theorists responsible for devising the inflationary model more than 20 years ago. Yet he shrugs off suggestions that he's trying to corner the cosmological market. "Having more than one theory is very important for motivating new experiments," he said.
Although he's excited by the possible implications of the new model, Steinhardt declined to bet on whether it or the conventional model is more representative of the nature of the universe.
"The conventional model has come out spectacularly well," he said, adding that he has nevertheless long wondered whether a different model might explain the universe equally wellor perhaps better. "That's what started us on this adventure," he said.
Steinhardt said several features of the cosmos can be better explained by the cyclic model, including the geometry of the universe, its overall uniformity, and, in particular, the existence of a phenomenon known as acceleration.
Recently gathered data from exploding, dying stars called supernovae have revealed that the universe is not only expanding, as predicted, but that its rate of expansion is accelerating. The only force that could explain such cosmic acceleration is a source of energy, not visible or yet identified by scientists, that permeates the entire universe. Physicists have dubbed the mysterious force "dark energy."
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