Rather Suspect

Physicists and philosophers sometimes speak about the “arrow of time” — this strange aspect of time in which it continues to move, and in only one direction. In my understanding, this is generally believed to be related to the increase in universal entropy.

In my last post, I spoke about how using spatial words (like understand) to describe time feels limiting. Today, I’d like to extend that just a bit and say that using a linear word would seem to be equally limiting.

That is, visualizing that we are somehow on a straight path that is moving in a particular direction — the past “behind” us, the future “ahead” — to my mind still allows us to fall into the trap of spatializing the idea of time. We even then go so far to speculate whether time travel is possible by bending time — as if the plan were to simply change the shape of that arrow.

But today I’d like to briefly explore a different mental model for time — instead of a straight arrow, would it be better to think of it as a rotation? Imagine our entire three-dimensional (spatial) universe existing as it always does — but instead of that universe somehow traveling along on a straight arrow, in fact we simply stand at the center and rotate that universe around us? There is perhaps still an “arrow” — but it is a curved arrow, already (and continuously) bending.

I often find language curious — and to that end I want to remark today on a single word: moment. We so often refer to a “moment” in time as an “instant” — but, in physics, the concept of a moment has a very specific meaning, which I’ll paraphrase as: a force or system of forces may cause an object to turn.

How curious that our language should evolve such that we use the word “moment” in our day-to-day to talk about time, but yet ignore the fact that we’ve also used it to describe a rotation.