Our universe was born about 13.7 billion years ago in a massive expansion that blew space up like a gigantic balloon.
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."
The Beginning
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.
At that point, they believe, the universe underwent an extremely brief and dramatic period of inflation, expanding faster than the speed of light. It doubled in size perhaps 100 times or more, all within the span of a few tiny fractions of a second.
But first, how did our universe spring up out of nothing? Cosmologists suspect that the four forces that rule the universe — gravity, electromagnetism and the weak and strong nuclear forces — were unified into a single force at the universe's birth, squashed together because of the extreme temperatures and densities involved.
Read Full Article: The Big Bang: What really happened at our universe's birth? (msn.com)