Nick Young in Psyche:
As you read this article, time will seem to pass. Right now, you are reading these words, but now you are reading these ones. What was present just an instant ago seems to have already slipped into the past. You will carry this feeling with you – as objects change and move, as thoughts run through your head, as feelings ebb and flow – until you fall asleep tonight. Heraclitus thought that time was like a river: ‘Everything flows and nothing abides; everything gives way and nothing stays fixed.’ Our experience of the world seems to back this up. It certainly feels as if time is sweeping us along. Yet, physicists and philosophers will tell you that Heraclitus was wrong. Time, they say, does not actually pass. In his book The Order of Time (2018), the Italian theoretical physicist Carlo Rovelli writes:
What could be more universal and obvious than this flowing?
And yet things are somewhat more complicated than this. Reality is often very different from what it seems. The Earth appears to be flat but is in fact spherical. The Sun seems to revolve in the sky when it is really we who are spinning. Neither is the structure of time what it seems to be: it is different from this uniform, universal flowing.
So, what is the real structure of time? Well, it’s complicated.