Those who weren't at the Tycho Brahe Planetarium in Copenhagen for the Setting Time Aright meeting last month can now watch the video of public panel discussion on "Understanding How Time Works, From Cosmology to Cognition." The panelists were Paul Davies, a theoretical physicist at Arizona State University, philosopher Tim Maudlin, from New York University, computer scientist (and "refugee physicist") Raissa D'Souza at UC Davis, and neuroscientist David Eagleman from the Baylor College of Medicine. The discussion was moderated by physics writer, author and SciAm blogger, Jennifer Ouellette.
If you don't have an hour to spare to watch the whole thing, below I've noted the position of various highlights that you can jump to. I've tried to credit the questions to those that asked them, where possible, because you can't see the questioners on the video -- but if I have left you off, then let me know.
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The first fifteen minutes or so introduces the speakers and some of the main problems with our understanding of time in physics, computer science and neuroscience: Does time flow? Can we understand time if we are embedded in it, like a fish trying to describe water? Does it make sense to say that a Gods-eye-view would look at the block universe from without? How is time related to complexity?
The floor was then opened to questions from the audience:
16:50 New Scientist's Rowan Hooper, via the magic of the interweb, asked whether time could have more than one dimension, noting that some physicists, such as Itzhak Bars, are currently looking into this. Could a second time dimension give meaning to the otherwise trivial statement that time flows at a rate of one second per second?
20:44 How does time work in a computer? Are we part of a computer simulation? Do we live in the Matrix? Paul Davis put forward a *reductio ad absurdum* argument against the cosmological multiverse in terms of simulated universes here, which goes something like: Simulated universes would be cheaper to construct than real ones, therefore, if we are in a cosmological multiverse with lots of other advanced lifeforms, and we are just arbitrary observers, then the chances are that others would have simulated a bunch of universes and we are more likely to be living in a fake universe than a real one. OK, within that simulation, we have concluded that we live in a cosmological multiverse, but that conclusion has no foundation because it is based on the examination of fake physical laws and we cannot conclude anything about the nature of reality based upon them.
24:33 George Musser, from Scientific American, asked how our temporal perception of the world operates when we play music or go dancing, adding that when he plays music as part of a band, he feels like "part of superorganism." In his response, David Eagleman ponders whether the energetic rewards felt by the brain on correctly predicting rhythm are related to the ways that people get pumped up to go to war.
26:25 A question from UCT cosmologist, George Ellis, "Could time be circular?" provokes a slight argument between Paul Davis and Raissa D'Souza about whether you would experience a different reality on your second time round the time-loop. Tim Maudlin steps in to sort things out.
31:37: Oxford University's David Wallace places the debate over the existence of time in context in terms of the history of science, noting that there is a tendency to first believe that everyday concepts are fundamental (for example, solidity), then swing to the other extreme arguing they do not exist at all (arguing that solid objects are an illusion, following the discovery of electrons and atoms), until finally "coming to our senses" and settling on a compromise view that the concept does exist, although it is not fundamental. Will that happen with time?
33:58: A question from Joy Christian of Oxford University: Can we begin to imagine finding a theory of everything in physics, if we cannot even include the flow of time in our equations? (This question does not make Paul Davies or Tim Maudlin happy.)
39:22 Why does time seem to slow when your life is in danger? What is the origin of "StairMaster time," where an hour of repetitive exercise seems like an eternity? David Eagleman explains that whether you perceive an event to have taken a long or a short time, depends on _when_ you are looking at it. During an exciting activity -- compared say, with when you are sitting on an airplane -- you don't have time to pay attention to the clock, so "time flies when you're having fun." But you also lay down a lot of new memories during this fun activity, so when you look back at it at a later date, the interesting activity seems to have taken up a longer, more significant portion of your life than, say, the boring plane journey that in hindsight seems to have passed in a flash because you laid down no novel memories during it.
Eagleman also touches on the question of the perceived flow of time in emergency situations, but he doesn't talk about it in much detail here, though he did earlier in the day, so I'll add a bit more about that now. Eagleman's team carried out tests to check whether time really does slow when you are in a life-threatening situation by throwing (willing) students off a 150-ft tower, along with a special wristwatch that flickers random digits at them. That flicker rate is just too fast for them to perceive the digits in normal circumstances. Since people in life-threatening situations claim that they can see the world in slow motion "like Neo in the Matrix," the idea is that while falling, they should be able to read these normally imperceptible digits. However, it turns out that they can't. (Though one wonders if looking at digits on their wrist would be a priority in that situation.) The conclusion is that people aren't actually seeing in slow motion. That means although you do have a distorted idea of duration, it's not like watching a movie that's been slowed down by stretching out the film. And, in fact, when you ask people who have been in car crashes more detailed questions, such as "did you notice sound being stretched out, with people's voiiiiices beeeeeing dissssstoooooorted?" they will say no.
41:51: Following on from the idea that duration and flicker rate are dealt with separately by the brain, bioengineer Malcolm MacIver asks whether the way that we understand each other's behavior will change as we get a better understanding of how time is fragmented in the mind and David Eagleman talks about how time is "metasensory."
44:49: Raissa D'Souza talks about how you might be able to apply the theory of phase transitions from physics to evolution (the Cambrian explosion) or to discussion of the multiverse (where new universes budding off would mark a transition), in response to a question by Nick Pritzker.
49:40: To wrap-up, having spent almost an hour chatting together, do the panelists, despite their different backgrounds, see points of commonality with each other?