It took quite a bit more than seven days to create the universe as we know it today.
Our universe was born about 13.7 billion years ago in a massive expansion that blew space up like a gigantic balloon.
That, in a nutshell, is the Big Bang theory, which virtually all cosmologists and theoretical physicists endorse. The evidence supporting the idea is extensive and convincing.
We know, for example, that the universe is still expanding even now, at an ever-accelerating rate.
Scientists have also discovered a predicted thermal imprint of the Big Bang, the universe-pervading cosmic microwave background radiation.
And we don’t see any objects obviously older than 13.7 billion years, suggesting that our universe came into being around that time.
“All of these things put the Big Bang on an extremely solid foundation,” said astrophysicist Alex Filippenko of the University of California, Berkeley. “The Big Bang is an enormously successful theory.”
So what does this theory teach us? What really happened at the birth of our universe, and how did it take the shape we observe today?
Traditional Big Bang theory posits that our universe began with a singularity — a point of infinite density and temperature whose nature is difficult for our minds to grasp.
However, this may not accurately reflect reality, researchers say, because the singularity idea is based on Einstein’s theory of general relativity.
“The problem is, there’s no reason whatsoever to believe general relativity in that regime,” said Sean Carroll, a theoretical physicist at Caltech.
“It’s going to be wrong, because it doesn’t take into account quantum mechanics. And quantum mechanics is certainly going to be important once you get to that place in the history of the universe.”
So the very beginning of the universe remains pretty murky. Scientists think they can pick the story up at about 10 to the minus 36 seconds one trillionth of a trillionth of a trillionth of a second after the Big Bang.
“Inflation was the ‘bang’ of the Big Bang,” Filippenko said. “Before inflation, there was just a little bit of stuff, quite possibly, expanding just a little bit. We needed something like inflation to make the universe big.”
During inflation, dark energy made the universe smooth out and accelerate. But it didn’t stick around for long.
Scientists don’t know what might have spurred inflation. That remains one of the key questions in Big Bang cosmology, Filippenko said.
Cosmologists and physicists are working hard to refine their theories and bring the universe’s earliest moments into sharper and sharper focus.
But will they ever truly know what happened at the Big Bang?
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