The Big Bang is commonly thought of as the start of it all: About 13.8 billion years ago, the observable universe went boom and expanded into being.
But what were things like before the Big Bang?Short answer: We don’t know. Long answer: It could have been a lot of things, each mind-bending in its own way.
The first thing to understand is what the Big Bang actually was.
“The Big Bang is a moment in time, not a point in space,” said Sean Carroll, a theoretical physicist at the California Institute of Technology and author of “The Big Picture: On the Origins of Life, Meaning and the Universe Itself” (Dutton, 2016).
So, scrap the image of a tiny speck of dense matter suddenly exploding outward into a void. For one thing, the universe at the Big Bang may not have been particularly small, Carroll said. Sure, everything in the observable universe today — a sphere with a diameter of about 93 billion light-years containing at least 2 trillion galaxies — was crammed into a space less than a centimeter across. But there could be plenty outside of the observable universe that Earthlings can’t see because it’s physically impossible for the light to have traveled that far in 13.8 billion years.