WASHINGTON — When the huge subatomic-particle smasher under the Swiss-French border starts running, it's supposed to reveal what happened the instant after the big bang, the theoretical beginning of our universe 13.7 billion years ago.
The Large Hadron Collider, which suffered a temporary setback last week, might find some answers. But it will leave other questions on many people's minds, such as what happened BEFORE the big bang, and even whether there was a "before."
A scientific mini-industry has popped up as deep-thinking physicists and cosmologists bat around various guesses as to what may have happened in a "pre-big bang.''
Some of the top minds in this field gathered at Columbia University earlier this month to debate these questions.
"What banged? Where did it come from?'' was the question raised by Laura Mersini-Houghton, a cosmologist at the University of North Carolina at Chapel Hill.
"Is ours the only universe? If so, how did it come to exist?'' asked Paul Davies, a cosmologist and authority on science and religion at Arizona State University in Tempe.
Respected scientists have proposed a flock of theories to describe what might have happened before the birth of our familiar universe of space and time.
The concepts have fanciful names such as "the big bounce," "the multiverse," "the cyclic theory," "parallel worlds," even "soap bubbles." Some propose the existence of multiple universes. Others hold that there's one universe that recycles itself endlessly, rather as Buddhists believe. Judeo-Christian theologians may have difficulty accepting any of these notions.
Most of the hypotheses are variations on an older idea that the universe has no beginning and no end, contrary to the big bang theory, which says that our universe originated at a specific point and will end sometime in the distant future.
"Neither time nor the universe has a beginning or an end,'' two leading cosmologists, Paul Steinhardt of Princeton University and Neil Turok of Oxford University, wrote in their 2007 book, "Endless Universe: Beyond the Big Bang.''
"The evolution of the universe is cyclic, with big bangs occurring once every trillion years or so, each one accompanied by the creation of new matter and radiation that forms new galaxies, stars, planets and presumably life,'' they wrote. "Ours is only the most recent cycle.''
Some scientists contend that observational evidence may be found to back up the speculation. They say that no scientific theory can be considered valid until it's been tested.
"It is becoming increasingly clear that multiverse models grounded in modern physics can be empirically testable,'' Max Tegmark, a theoretical physicist at the University of Pennsylvania, Philadelphia, wrote in "Parallel Universes,'' a chapter in a 2003 book "Science and Ultimate Reality.''
Some researchers hope that the Large Hadron Collider will provide evidence to support or refute these conjectures. They say the particle smasher might discover extra dimensions, beyond our familiar three spatial dimensions plus time. More dimensions are the basis of several pre-big bang theories.
Michio Kaku, a professor of theoretical physics at the Graduate Center of the City University of New York, proposes that gravity, unlike light and matter, could travel between parallel universes and cast a "shadow'' that scientists might be able to detect.
The shadow might take the form of "gravitational waves,'' faint ripples in the fabric of space and time caused by violent explosions such as the big bang. Detectors in the United States and Europe are seeking such waves, and in the future satellites will watch for evidence of them in space.
Turok says his cyclic theory predicts a "distinctive pattern of gravitational waves that is very different from the one expected in the big bang theory . . . and may prove or disprove our theory within the next few years.''
Last August, ground and satellite observations revealed what appeared to be an enormous "hole in the universe,'' a mostly empty region of the sky, 900 million light-years wide — about 5 billion trillion miles — in the constellation Eridanus. Mersini-Houghton, a believer in multiple universes, interpreted the empty spot as the "footprint'' of the gravitational tug of another, smaller universe parked at the edge of our own.
"It's like someone took a giant scoop and scooped all the matter away,'' she told the Columbia cosmology conference. "All these universes are interacting with each other.''
Mersini-Houghton's interpretation of the "hole'' is controversial and so far lacks independent confirmation.
The oldest and most popular of the pre-big-bang theories is the multiverse. As outlined by Martin Rees, the British astronomer royal, in his 1997 book, "Before the Beginning: Our Universe and Others,'' the theory declares that our universe is only one of many — perhaps an infinite number — of other worlds, each differing slightly from the others. These universes are continually forming new offspring, sprouting off from each other rather like soap bubbles.
The big bounce hypothesis — sometimes known as the big splat — contends that our universe was preceded by a twin that expanded to a certain limit, then contracted, collapsed and gave birth to our world. A leading proponent of this theory is Martin Bojowald, a theoretical physicist at Pennsylvania State University in University Park, who published it last year in the journal Nature.
In 2005, Kaku published a book titled "Parallel Worlds'' in which he hypothesized that there may be millions of different, parallel universes, some that look like our own. They're invisible to us because they lie outside our universe.
The big bang theory found favor with the Roman Catholic Church because it implied that the world has a single beginning at a definite point in time, as portrayed in Genesis. At a Vatican conference in 1951, Pope Pius XII said the big bang was consistent with church doctrine.
"Creation took place in time, therefore there is a creator, therefore God exists!" the pope declared.
The Rev. John Haught, an authority on science and religion at Georgetown University in Washington, said the idea that there might be many worlds and many beginnings, not just a single big bang, wouldn't undermine Christian theology.
"Even if the universe, or multiverse, were around forever, this would not challenge the theological explanation of the world's existence,'' Haught said. "The biblical doctrine of creation . . . lies at a different level from scientific understanding. The world, theologians say, still gets its finite being from an infinite being.''
According to Francisca Cho, a professor of Buddhism and East Asian religions at Georgetown, these pre-big bang cosmologies are similar to the Hindu belief in a universe that cycles endlessly through creation and destruction.
ON THE WEB
Video of the cosmology conference at Columbia University
Video of Neil Turok's lecture ``What Banged?''
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