The Big Bang Wasn’t The Beginning, After All
“The Universe began not with a whimper, but with a bang! At least, that’s what you’re commonly told: the Universe and everything in it came into existence at the moment of the Big Bang. Space, time, and all the matter and energy within began from a singular point, and then expanded and cooled, giving rise over billions of years to the atoms, stars, galaxies, and clusters of galaxies spread out across the billions of light years that make up our observable Universe. It’s a compelling, beautiful picture that explains so much of what we see, from the present large-scale structure of the Universe’s two trillion galaxies to the leftover glow of radiation permeating all of existence. Unfortunately, it’s also wrong, and scientists have known this for almost 40 years.”
Did the Universe begin with the Big Bang? When we discovered the cosmic microwave background, and its properties matched exactly the prediction of the Big Bang theory, it was a watershed moment for cosmology. For the first time, we had uncovered the origins to the entire Universe, having learned where all of this came from at long last. Emerging from a hot, dense, expanding, and cooling state, the matter-and-radiation-filled early Universe gave rise to everything we see today. Except there were a few pesky problems that the Big Bang couldn’t explain. If the Universe truly emerged from an arbitrarily hot, dense state, and if space and time themselves were born at that exact moment, the Universe would have signatures that we simply don’t see. Instead, theorists came up with an alternative beginning: cosmic inflation. Inflation made a bold prediction about the scale and magnitude of the fluctuations that should arise from this early state, and when our technology finally caught up to our imaginations, we measured them.