Cyclical theory of universe proposed

Space and time go on forever, and the so-called big bang said to have started the universe is actually part of a repeating cycle, according to a new paper that challenges conventional wisdom in physics.

Infinite space and time would contradict the generally accepted idea of a universe expanding abruptly out of nothing 14 billion years ago, said Neil Turok, professor of mathematical physics at the University of Cambridge in England. Turok wrote the paper in the journal Science with Paul Steinhardt of Princeton University.

The study began as an attempt to explain the energy found in vacuums, which is credited with accelerating the universe's expansion. If the energy had been around since the big bang, Turok said, it should have blown the universe apart.

The study's authors looked at why the force of the expanding universe, known as the cosmological constant, is much smaller than would be expected under the big-bang theory. Physicists previously explained the discrepancy by introducing ''inflationary energy," Turok said.

Turok and Steinhardt calculated that space and time could continue forever. Two infinite three-dimensional spaces touch one another every trillion years or so, sparking great explosions of radiation and creating new matter, a process we detect as the big bang, they reported.

The authors' theory faces skepticism. In a companion article in Science, Alexander Vilenkin, director of the Tufts Institute of Cosmology in Medford, said the traditional big-bang theory remains more convincing.

The authors' new theory can be disproved by observations of gravitational waves in the universe, Vilenkin said. A NASA probe a million miles from Earth is trying to find the waves, which the new theory says shouldn't exist.