If I had the time, I would… How would you complete the sentence? Why does it seem like time can go by very slowly, at times, and sometimes it can go by very quickly? How do we get lost in time? How can we have such different experiences, and often different from others having the same experience, with this thing we call time? What is it?
The short answer is that nobody knows. What time is and why it exists have perplexed people for as long as people have asked questions. We know that we can measure it. Until we can’t, because it is relative to the observer, as Einstein taught. At least we know it exists. Until we don’t, as physicists have taught us. So, what do we experience, why do we experience it, and is this experience useful? Or does this experience mislead us? In these recommended readings, two physicists and a philosopher explore these questions.
MIT philosophy professor Bradford Skow guides us through frameworks that describe our experience of time with the block universe and moving spotlight theories. These theories provide possible ways of understanding, robustly, what it means to experience the passage of time. Is time moving, or are we moving? Is there one time or branching time? Why does time seem to speed up or slow down? Professor Skow invites us to explore the rigor of the underlying philosophical claims that these frameworks bring to these questions about our experience.
Physicist Julian Barbour invites us to explore time as a series or set of “nows,” where “time is nothing but change…change is the measure of time, not time the measure of change” (p2). How can we understand our experience of time, if “time does not exist at all, and..motion itself is pure illusion” (p4)? Building on Einstein and Mach, Barbour suggests that “The proper way to think about motion [change in space over time] is that the universe as a whole moves from one ‘place’ to another ‘place’, where ‘place’ means a relative arrangement, or configuration, of the complete universe…the universe…does not move in absolute space, it moves from one configuration to another…History is the passage of the universe through a unique sequence of states” (p69).
Cal Tech professor of physics Sean Carroll provides a relatively user-friendly exploration of the physics of the arrow of time, through an understanding of entropy, Einstein’s special and general relativity, quantum theory, and black holes.
For me these readings have opened up my awareness to what I am experiencing when I think it is time. Seeing choice points, choices that otherwise I tend to lose in time.