Thank you all for the comments -- I will reply to a few of them here, and if time permits (so to speak) I may tackle a few more later on.

Bob: As the comment from “Robespierre” points out, the French indeed tried to introduce “metric time” during the revolution -- it didn’t catch on. Nicholas: I’m not an expert on Bergson, but I don’t think there’s much support within physics for any kind of “pure” or “metaphysical time,” whatever that may be construed to mean. Although it is hard to accept -– and this lies at the heart of my final chapter in “In Search of Time” -- for today’s physicists, time is simply what one reads off a clock. I appreciate that many people find this unsatisfying. Jason: Yes indeed! (And “Longitude” is a great book.) David: This is an excellent point. Time is clearly linked to space –- special relativity makes that abundantly clear -– but we experience time in a way that seems quite distinct from space. Thermodynamics -– as I relate in Chapter 6 (and in more depth in Chapter 10) does hint at why time has a direction, but there are many unresolved problems. Monica: I loved “Einstein’s Dreams.” There was a stage production at MIT a few years back.

There is a wonderful little book called "Einstein's Dreams" by Alan Lightman. Though fictive in nature, it investigates multiple experiences of time. I found it brilliant, and poetic. Especially for it's very human core.

I believe that time and light are interwoven. When time slows down, light speeds up and becomes a wave. When time slows down, light becomes matter - a photon. We see light as both things at the same time because we do not see time on that tiny scale. In E=mc2, m and c are fluctuating. We just do not see it happen.

Not to worry. By the definition of science alone, Einstein's conclusions will eventually be found to have been wrong. In fact, the limiting speed of light has already been exceeded.
Dr. Andy

I've always wondered why we refer to time as a dimension, and yet is is so clearly different from the spatial dimensions. Thermodynamics only works in one direction! This seems to be telling us something.

Do different atomic and subatomic particles have their own notion of time? i.e. their own clocks? If so, how is there any notion of time at all?

Is it all coincidence (which is a really bad word to use for time)?

Hi Dan. Great conversation. What is your opinion on the time and information paradox? Is it possible that time loops or that possibilities of our actions can play out in other dimensions?

Speaking of time and navigation, weren't accurate timepieces critical in the development of East-West sea travel?

Accurate measurement of time was very crucial to navigation at sea. It was used to find longitude, which was very difficult to accurately find prior to the invention of a sea worthy clock which didn't operate with a pendulum. John Harrison was a clock maker who invented these first such clocks in the early 1700's. I read this in a very interesting book called Longitude by Dava Sobel.

can you comment on how the concepts of beginning & end of time affected the measurement of time?

Just for the record, I would like to mention to you and fellow listeners the most wonderful book on time that I have ever read:

"Revolution in Time," by David S. Landes, Coolidge Professor of History and Professor of Economics, Emeritus, Harvard University. Published in 2000, it is a magisterial work on this subject.

Given the comment on Bergson regarding his lived time vs. mathematical time, and the statement on the lack of a perfect clock: What can be said for the actual argument for a "pure" or "metaphysical time?" I must say that I do not keep up with physics, but is there even a pure physics at this point which we could base some "pure time" one.

In addition, to the previous comment which is also of great interest, please ask your guest to comment on the issues of " How would one tell time should we start to explore the galaxy?

Do we use the earth as the reference point or somewhere else? Or is there some way to tell absolute time?

I tried to install metric time once during the French Revolution, but my fellow countrymen weren't interested in my ingenious metric week. Damned FOOLS!

Why is there no equivalent of the metric system for time? As someone who grew up in a country that converted to the metric system, and now struggles (even after 20 years) to convert back because I live in the US, I have often wondered why we can't redefine minutes and hours so that there are 10 hours in a day, each with 100 minutes. And why not have 10 equal length months (except for leap days, which would not be in any month, and would be holidays). I haven't worked out all the details, but has this been tried anywhere?