by Sabine Hossenfelder
Did the Big Bang happen? Has the James Webb Space Telescope found evidence against the Big Bang? If astrophysicists are sure the Big Bang happened, why do they also think the universe was born from a quantum fluctuation? And what does this have to do with dark matter?
I can’t blame readers for being confused by recent news stories about the Big Bang. The articlethat kicked them off, “The Big Bang Didn’t Happen,” is bad enough. But some of the rebuttals also don’t get it right. The problem is that writers conflate ideas in astrophysics and use the term “Big Bang” incorrectly. Let me set the record straight.
Let’s call Big Bang #1 the beginning of the universe. It’s what most people think the expression means. This Big Bang is what we find in the mathematics of Einstein’s general relativity if we extrapolate the current expansion of the universe back in time. The equations say that matter and energy in the universe becomes denser and hotter until, eventually, about 13.7 billion years in the past, both density and temperature become infinite. We cannot extrapolate any further back in time, so it’s fair to say that this event, if it happened, would be the beginning of the universe. … (continue at Nautilus)