Sunday, February 07, 2021

As I was walking down the street one day

I think about time a lot. I have a cesium atomic clock "ticking" away in my living room. I've stood alongside one of the official cesium frequency references, and also the experimental ytterbium optical atomic clock, at the NIST laboratories in Boulder Colorado.


For a long time, I thought there wasn't really any such thing as time per se, only events connected by causality. After all, all of our means of measuring time have to do with counting events that occur in some naturally occurring resonator: pendulum, quartz crystal, cesium atom, etc. This is a point of view held by at least some research physicists, so it's not a completely crazy idea.

But in one of Dr. Sabine Hossenfelder's blog posts, a commenter mentioned the effects of special and general relativity on our measurement of time, in which acceleration and gravity wells, respectively, slow time down, according to those very same resonators. That comment completely changed my world view. So now I think time is a real thing, not just a measurement artifact.

Next thing to think about: why does time play a role in the large (classical physics, cosmology, etc.) but not in the very small (where it doesn't appear as a factor in the equations used by quantum physicists)?

Separately: what sometimes keeps me awake at night (really) is that there is much evidence that at both the quantum (Bell's Theorem) and cosmological ("block time" a.k.a. "block universe") level, reality appears to be super deterministic: both the past and the future are fixed, and we are just passive observers playing our roles as we move along the timeline. We can't predict the future; but we can't change it either.

Does anybody really know what time it is?


Tristan Slominski said...

Things I found recently that relate to this theme (at least for me) are Mark Burgess' Smart Spacetime book, and in general, the world of Promise Theory.

Also, I think that Brouwer's "intuitionist" mathematics feels like the "real" thing (reminded about it in this Quanta article: Does Time Really Flow? New Clues Come From a Century-Old Approach to Math). Nicolas Gisin seems to be pursuing that approach. The approach seems compelling, especially after watching Robert Harper's lecture series relating types, categories, and logic in the various Oregon Programming Languages Summer School seminars.

Chip Overclock said...

Tristan: Thanks much for the pointer to the Quanta article. I read it this morning and found a lot of useful insights in it. I recommend it to anyone else interested in this topic. :Chip