A team at the University of North Carolina has proposed a new theory that shows the universe can endlessly expand and contract, contradicting the Big Bang theories and responding to a thorny modern physics problem.
The new cyclic model is made of four key parts: expansion, turnaround, contraction and bounce.
During expansion, dark energy, the mysterious force provoking the universe to expand at a speedy rate, expands until all matter fragments into patches so far apart that there's no matter to bridge the gaps and everything from black holes to atoms disintegrates, a phase called turnaround.
At that point, each fragment contracts individually instead of pulling back together in a reversal of the Big Bang, turning into an countless number of independent universes that contract and then start bouncing outward, reinflating in a manner similar to the Big Bang.
Our universe would be one of these patches. "This cycle happens an infinite number of times, thus eliminating any start or end of time," said Dr. Paul Frampton, professor of physics. There is no Big Bang."
"Cosmologists first offered an oscillating universe model, with no beginning or end, as a Big Bang alternative in the 1930s. The idea was abandoned because the oscillations could not be reconciled with the rules of physics, including the second law of thermodynamics," Frampton said.
The second law says entropy (a measure of disorder) can't be erased; instead, it grows from one oscillation to the next and the universe increases with each cycle. "The universe would grow like a runaway snowball," Frampton said. "Extrapolating backwards in time, this implies that the oscillations before our present one were shorter and shorter. This leads inevitably to a Big Bang," he said.
As this theory says each "causal patch" turns into a separate universe, then each universe would contract essentially empty of matter and entropy. "The presence of any matter creates insuperable difficulties with contraction," Frampton said. "The idea of coming back empty is the most important ingredient of this new cyclic model."
"I suddenly saw there was a new way of solving this seemingly impossible problem," he said.
"I was sitting with my feet on my desk, half-asleep and puzzled, and I almost fell out of my chair when I realized there was a much, much simpler possibility."
The new theory also changes the model about the dark energy's equation of state, describing its pressure and density, assuming for it always a value below -1, in contrast to a 2002 similar cyclic model which stated an equation value never below -1. The negative value of the equation stops the universe from blowing itself apart irreversibly in a "Big Rip."
This way, the density of dark energy is similar to the density of the universe and the expansion phase ceases just before the Big Rip. "New satellites currently under construction, such as the European Space Agency's Planck satellite, could gather enough information to determine dark energy's equation of state," Frampton said.