WHAT CAME BEFORE BIG BANG

Whenever a cosmologist gives a public lecture, someone in the audience inevitably raises a hand to ask, "Yes, but what came before the Big Bang?"

"There's this textbookanswer that

we're supposed to give," says Glenn

Starkman, a physicist at Case

Western Reserve University. "We say

that the question is meaningless, just

as it's meaningless to ask what's

south of the South Pole."

The idea is this: If time itself began

with the Big Bang, then it makes no

sense ask what came before. There

simply was no "before." And yet

Starkman knows that hardly anyone

finds that answer satisfying.

We now have a model for what happened very shortly after the Big Bang. During the first tiny fraction of a second of the universe's existence, the

"inflation" model says that the universe expanded like a balloon, doubling in size again and again before slowing down to its "normal" rate of expansion. But if we try to look back before inflation -all the way back to "time zero"-general relativity

breaks down.

Some physicists nowthink that time didn't begin with the Big Bang, but somehow emerged when the universe reached a certain level of complexity. Others theorize that the universe runs in cycles, in a possibly endless series of expansions and

contractions. If this "cyclic" model is right, the Big Bang wasn't the beginning, but just a transition from an earlier era. Another possibility is that our universe is just one of countless "bubble universes" that pop up repeatedly in a "multiverse."

Are we any nearer to answering the "what came before" question that we were a generation ago? Starkman says no. And it's unclear whether astronomical observations can settle the matter.

Our best bet might be to build an enormous gravity wave detector in space with the hope that we could detect gravitational waves created by the Big Bang itself.

But don't hold your breath.Starkman says such an Enormous project could take

many decades to build.