Time

We’ve mentioned before that Richard Feynman was way ahead of his time when it came to the need to understand cosmological initial conditions and the low entropy of the early universe. (Among other things, of course.) Feynman actually wrote three different books in the early 1960’s — in his way of “writing books,” which consisted of giving lectures and having others transcribe them — all of which made a point of discussing this problem. The Character of Physical Law was aimed at a popular audience, the Feynman Lectures on Physics were aimed at undergraduate physics majors, and the Feynman Lectures on Gravitation were aimed at advanced graduate students — and in every case he emphasized that we can only account for the Second Law of Thermodynamics by assuming a low-entropy boundary condition in the past, for which we currently have no reliable explanation. (These days we have a larger number of speculations, but still nothing reliable.)

Here’s a video clip from about ten years afterward, in 1973, where Feynman raises a similar point in a conversation with Fred Hoyle, the accomplished astronomer and a pioneer of the Steady State cosmology. (Thanks to Ronan Mehigan.) They don’t go into details, but Feynman introduces the idea as a kind of meta-issue in physics:

“What, today, do we not consider part of physics, which we may ultimately be part of physics?”

His answer (which should be cued up here at the 7:10 mark) is the initial conditions of the universe, as well as the possibility that the physical laws themselves evolve with time. (Conversation continues for a tiny bit in the followup video. Listen on to hear Feynman explain how he doesn’t like to speculate about things.)

What’s interesting is that now, four decades later, it’s commonplace to address the issue of initial conditions in a scientific context, and even to consider the evolution of local physical laws, as we do with the multiverse and the string theory landscape. I’m not sure what is the precise history of this endeavor, but in the very same year this interview was aired, Collins and Hawking wrote an early paper asking why the universe is isotropic. In 1979, Dicke and Peebles published “The Big Bang Cosmology — Enigmas and Nostrums,” which set out many of the puzzles that Alan Guth would attempt to address with the inflationary universe scenario. When we marry inflation with the idea of a landscape of vacua (whether from string theory or elsewhere), we naturally are led to the idea of an evolving set of local physical laws, raising the possibility that we might be able to actually explain (using the anthropic principle or simple probability arguments) why we observe one set of laws rather than some other. Not that we have, or even seem very close, but the scientific agenda is clear.

So how could we answer Feynman’s question today? What do we not consider part of physics, which someday we might?

With The Particle at the End of the Universe scheduled to come out in November, most of the popular-level talks I’ll be giving in the near future will have to do with the LHC and the Higgs boson — and quantum field theory, as part of my secret agenda to get QFT accepted as part of the mainstream pop-sci vocabulary. So I’ll be giving fewer talks about the arrow of time, at least near-term. I thought I’d commemorate the occasion by sharing the slides I used for a recent version of this talk: “The Origin of the Universe and the Arrow of Time.” Not that I’m by any stretch done talking about it, but hopefully the next time the occasion arises I’ll have the energy to make up new slides from scratch.

Andy Albrecht of UC Davis gave an entertaining TEDx talk on entropy — or as he calls it, “destruction” — and the arrow of time. I especially like how he is willing to look clumsy in the cause of greater pedagogy!

“Perhaps no one comprehends the roots of depravity and cruelty better than Philip Zimbardo.” At least, that’s what it says here. They’re referring to the fact that Zimbardo — a psychologist who long ago supervised the notorious Stanford Prison Experiment (chilling video here) — is an expert on the psychology of “evil” behavior. But he’s also an expert on the psychology of time, which we can all agree is much more interesting.

I recently got to hear a talk by Zimbardo, in which among other things he discussed the Stanford Marshmallow Experiment — a rather more adorable experience than the prison experiment, from what I understand. The Marshmallow experiment, originally conducted by Walter Mischel in 1972, was aimed at understanding how we think about different times — the future vs. the present. Children were asked to do some easy tasks, and then were rewarded by being given a marshmallow. But! They were told that the experimenter had to step outside for a few minutes, and if they could just sit tight and not eat their marshmallow until he came back, they could have that and also an additional marshmallow.

It’s a matter of future vs. present rewards. It’s natural (and totally rational) to discount rewards that are promised in the future — after all, the future is hard to predict, and anything can happen. If I offered you a choice between $4 today and $5 ten years from now, you’d be sensible to take the lower amount today — depending on how much you trusted me, of course. But if there is a good reason to trust, and the future isn’t that far off, it makes sense to delay gratification a bit. So what happens when some four-year-olds are put to the test?

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Time and MarshmallowsRead More »

For you arrow-of-time freaks who have been looking for a quick and engaging intro to the issues (maybe to show your friends to get them to appreciate your obsession), here’s a guest spot I did for the terrific Minute Physics series illustrated by Henry Reich. If you’re not already familiar with them, check out the entire series.

The Arrow of Time feat. Sean Carroll

Previously I did one on dark energy. It came out right after the Nobel Prize announcement, but don’t let that trick you into thinking I won the Prize myself. (Some people were tricked.)

2011 Nobel Prize: Dark Energy feat. Sean Carroll

Meanwhile, in a parallel universe, instead of writing Spacetime and Geometry, I wrote a massive tome on Cosmology. This parallel universe was featured on this week’s episode of Fringe. Here’s Walter Bishop retrieving his copy from Peter.

I helped with some of the equations on the episode. Thanks to Glen Whitman and Rob Chiappetta for the shout-out.