Ask Ethan: Does time exist, or is it an illusion? | by Ethan Siegel | Starts With A Bang! | Jul, 2024

The passage of time is something we all experience, as it takes us from one moment to the next. But could it all just be an illusion?

One of the most important aspects of physics, or of any science in general, is to always muster up the greatest challenge to the leading physical theories you can. You can challenge prior results, you can challenge the methods used to obtain them, you can concoct new tests in new regimes of potential applicability, and you can even challenge the assumptions underlying them. When it comes to our understanding of the Universe, we believe that we inhabit a four-dimensional “fabric” known as spacetime, with three spatial dimensions and one time dimension, all of which are inextricably woven together.

All of this assumes, of course, that time itself is a real thing: physically real, and fundamental in nature. But are these assumptions necessarily true? Is there any way possibly around them, and could time instead be merely an illusion, albeit a convincing one? That’s what Dave Drews wants to know, as he writes in to ask:

“We’ve all heard the philosophical question, ‘If a tree falls in a forest and no one is around to hear it, does it make a sound?’ Some people think time is an illusion, a construct of human minds and experience. If that’s true, then if there were no sentient beings…