“The only reason for time is so that everything doesn’t happen at once.” -Albert Einstein
And yet, this is a very good reason! We need things to happen in stages: you can’t form human beings before you form planets (that would be bad); you can’t form stars before you form atoms (also bad); you can’t form atomic nuclei before you get rid of antimatter (still bad).
But somehow, despite having very little direct evidence for what happened in the early Universe, we tend to give timelines of precisely when various events happened. For this week’s Ask Ethan, we take a look at how well we actually know these pieces of information, and why we think we can state any of this with confidence.