303 | AMA | February 2025

13161.604 - 13185.526 Sean Carroll

That equation we referred to earlier, the Friedmann equation of general relativity, is literally an equation for the scale factor as a function of time. So it is true that time is measured by clocks. But that's not all time is. Time exists as a parameter in our best physical descriptions of the world. And in that role, it absolutely has true meaning, even one second after the Big Bang.