Time

I don’t suppose “cornucopia” is the right collective noun, but what does one call a collection of talks centered on the subject of time? I previously linked to these talks from our time conference, but it’s clear from the viewing numbers that not nearly enough of you have taken advantage of them. There’s a lot of great stuff here! So let me pick out some of my very favorites, although I promise they are all good.

Here’s neuroscientist David Eagleman, talking about how we perceive time.

David Eagleman on CHOICE

Here’s physicist-turned-complexity-theorist Raissa D’Souza, talking about complexity.

Raissa D'Souza on COMPLEXITY

Here’s another physicist-turned-complexity-theorist, Geoffrey West, taking the complexity story even further.

Geoffrey West on COMPLEXITY

Here’s former guest-blogger, now Discover blogger, and engineer/roboticist/neuroscientist/philosopher Malcolm Maciver, talking about making choices and the evolution of consciousness.

Malcolm MacIver on CHOICE

And to top things off, here’s one of those mock debates (where participants attempt to defend the side they don’t believe in). This time it’s David Albert vs. David Wallace, on the many-worlds interpretation of quantum mechanics.

A Mock Debate on Quantum Mechanics with DAVID ALBERT and DAVID WALLACE

Seriously good stuff. There are still more talks not yet up, I’ll let you know.

Update: I didn’t realize my own talk was up. Here it is.

Sean Carroll, OPENING PANEL at FQXi Conference on Time

“Time” is the most used noun in the English language, yet it remains a mystery. We’ve just completed an amazingly intense and rewarding multidisciplinary conference on the nature of time, and my brain is swimming with ideas and new questions. Rather than trying a summary (the talks will be online soon), here’s my stab at a top ten list partly inspired by our discussions: the things everyone should know about time. [Update: all of these are things I think are true, after quite a bit of deliberation. Not everyone agrees, although of course they should.]

1. Time exists. Might as well get this common question out of the way. Of course time exists — otherwise how would we set our alarm clocks? Time organizes the universe into an ordered series of moments, and thank goodness; what a mess it would be if reality were complete different from moment to moment. The real question is whether or not time is fundamental, or perhaps emergent. We used to think that “temperature” was a basic category of nature, but now we know it emerges from the motion of atoms. When it comes to whether time is fundamental, the answer is: nobody knows. My bet is “yes,” but we’ll need to understand quantum gravity much better before we can say for sure.

2. The past and future are equally real. This isn’t completely accepted, but it should be. Intuitively we think that the “now” is real, while the past is fixed and in the books, and the future hasn’t yet occurred. But physics teaches us something remarkable: every event in the past and future is implicit in the current moment. This is hard to see in our everyday lives, since we’re nowhere close to knowing everything about the universe at any moment, nor will we ever be — but the equations don’t lie. As Einstein put it, “It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.”

3. Everyone experiences time differently. This is true at the level of both physics and biology. Within physics, we used to have Sir Isaac Newton’s view of time, which was universal and shared by everyone. But then Einstein came along and explained that how much time elapses for a person depends on how they travel through space (especially near the speed of light) as well as the gravitational field (especially if its near a black hole). From a biological or psychological perspective, the time measured by atomic clocks isn’t as important as the time measured by our internal rhythms and the accumulation of memories. That happens differently depending on who we are and what we are experiencing; there’s a real sense in which time moves more quickly when we’re older.

4. You live in the past. About 80 milliseconds in the past, to be precise. Use one hand to touch your nose, and the other to touch one of your feet, at exactly the same time. You will experience them as simultaneous acts. But that’s mysterious — clearly it takes more time for the signal to travel up your nerves from your feet to your brain than from your nose. The reconciliation is simple: our conscious experience takes time to assemble, and your brain waits for all the relevant input before it experiences the “now.” Experiments have shown that the lag between things happening and us experiencing them is about 80 milliseconds. (Via conference participant David Eagleman.)

5. Your memory isn’t as good as you think. …

Ten Things Everyone Should Know About TimeRead More »

Neuroscientists have all the fun. When we physicists think about the fundamental nature of time, it largely involves standing hopefully in front of a blackboard and writing the occasional equation, or at best sending clocks on strange journeys. All in the service of very good ideas, of course. But when I give talks about these wonderful ideas, I learn that what people care more about are down-to-earth questions about aging and memory. So not only do neuroscientists get to tackle those questions directly, but they do so by dropping people from tall buildings. How cool is that?

David Eagleman is an interesting guy, as a recent New Yorker profile reveals. Mild-mannered neuroscientist by day, in his spare time he manages to write fiction as well as iPad-based superbooks. But his research focuses on how the mind works, in particular how we perceive time.

I’ve written previously about how, as far as the brain is concerned, remembering the past is like imagining the future. Eagleman studies a different neurological feature of time: how we perceive it passing under a variety of different conditions. You might be familiar with the feeling that “time slows down” when you are frightened or in some extreme environment. The problem is, how to test this hypothesis? It’s hard to come up with experimental protocols that frighten the crap out of human subjects while remaining consistent with all sorts of bothersome regulations.

So Eagleman and collaborators did the obvious thing: they tied subjects very carefully into harnesses, and threw them from a very tall platform. The non-obvious thing is that they invented a gizmo that flashed numbers as they fell, so that they could determine whether the brain really did speed up (perceiving a larger number of subjective moments per objective second) during this period of fear.

Answer: no, not really. There is a perceptual effect that kicks in after the event, giving the subject the impression that time moved more slowly; but in fact they didn’t perceive any more moments than a non-terrified person would have. Still, incredibly interesting results; for example, when you’re afraid, the brain lays down memories differently than when you’re in a normal state.

Obviously, of course, these findings need to be replicated. If you’ll excuse me, I’m off to find some grad students and a tall building.