Does Time Exist?

Videos from our Setting Time Aright conference are gradually filtering online, courtesy of the Foundational Questions Institute. Perhaps the very first question that should be asked, of course, is whether the subject of the conference actually exists. So we recruited two well-known partisans on this issue to hash things out. Tim Maudlin is a philosopher of science who has argued forcefully that time is real — and furthermore that the arrow of time is an intrinsic part of reality, not just a byproduct of the low-entropy Big Bang. (Crazy talk.) Julian Barbour is a physicist who is well known for arguing that time doesn’t really exist, we can happily eliminate it from all of our equations of physics. (Even crazier.)

So we asked them to go at it, with a twist: here Tim defends the proposition that time doesn’t exist, while Julian argues that it is real. I was not the only one to conclude that these guys were just as good at arguing this side as the one they actually believed.

Well worth watching — both talks are quite brilliant, in very different ways.

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33 Responses to Does Time Exist?

  1. Dave says:

    Video removed by user =(

  2. Peter says:

    The video seems to be down 🙁

  3. Bahador says:

    “This video has been removed by the user” 🙁

  4. Sean says:

    Fixed! That’s what I get for scheduling a post ahead of time.

  5. thanosk says:

    Check your link to YouTube
    I get “This video has been removed by the user. “

  6. mma says:

    link is broken, video removed by user.

  7. ts says:

    Video doesn’t work beyond 3:08

  8. Henry says:

    “This video has been removed by the user.”

    Any chance we can get a fixed link?

    Edit: Aaaaand nevermind.

  9. chabuhi says:

    In the meantime, here’s a great Through The Wormhole episode on the subject:

  10. Pietr Hitzig says:

    I found this link

    There was a small hitch. I had to lower the baud rate before it started. This may be my internal problem.

  11. Sean says:

    The link is working now, honestly. You might have to reload the page.

  12. Stephen Crowley says:

    I’ll let you guys in on a little secret. There is an extraordinary mind-bending interplay between the observer(s) watching the video(INCLUDING the delivery mechanism, internet, routing, saved file on hard drive, etc) and experiencing a succession of time via sequences of flashing pixels and the and states of the minds of the participants in the video (witting AND unwitting, which has non-trivial consequences when it comes to surveillance) which is being watched “later”. Many times videos are made unavailable because the “connection” between viewer and viewee becomes too entangled with environment and chaos breaks out and frightens people.

  13. Georg says:

    There is no time, and Julian is its prophet.
    (BTW, how does prophecy work without time?)

  14. Ed Minchau says:

    The Lorentz equations and the electronics equations governing capacitors, inductors, and filters all require *two* orthogonal dimensions of time. If those FTL neutrinos observed at CERN had actually turned out to be traveling faster than light, we’d have been forced to either change the Lorentz equations or concede that there is indeed a second time dimension.

  15. Mike Empyema says:

    If time does not exist, how does one rationalize the sudden absence of sucessive time derivatives of position (and times mass) – velocity (momentum), acceleration (force), jerk (yank), snap (tug), crackle (snatch), pop (shake).

    Momentum is good stuff – the Periodic Table arises from it. Absence of acceleration does bad things to the Equivalence Principle and General Relativity – gonna use string theory, are ya? Saying that a pendulum is stationary in 4-space does not clear you from being late to your employment interview.

    Theory predicts what observation tells it to predict. Theorists boast of their promiscuity while empiricists quietly pay child support.

  16. Eunoia says:

    I have a question, Sean.

    If the universe (aka spacetime) is expanding, does this mean time is ‘dilating’ as well?

    And can you explain to us what that means? I didn’t even understand my own question in any depth 😉

  17. Sean says:

    It just means that space is expanding, as a function of time. “Time expanding” isn’t a very meaningful concept.

  18. Christian Ready says:

    I don’t think I’ve ever quite gotten my head around the concept that time is an illusion. Relative to the observer? Of course. Bi-directional? Perhaps. But nonexistent? Ok that has me stumped. Otherwise, there wouldn’t be any change at all, right?

  19. KernelMethod says:

    “If time does not exist, how does one rationalize the sudden absence of sucessive time derivatives of position..”

    One doesn’t need to. Limiting discussion even to the classical regime, the essence of Barbour’s work* as I understand it is that it renders unnecessary any a priori assumption of the existence of time. Best matching of configuration spaces, the use of what Barbour calls a “Jacobi-type action”, and treating reparameterization-invariance as a guiding principle is sufficient to produce everything you see in Newtonian physics.

    Extending this to gravity appears to be promising as well providing that you (i) accept that Dirac really was onto something when he claimed to believe that the universe really isn’t four-dimensional, (ii) accept that the space of Riemannian three-metrics modulo diffeomorphisms probably has something really fundamental to tell us, and (iii) recall that the ADM decomposition of general relativity is, in many respects, even more elegant than the fully four-dimensional version.

    Barbour’s work really does contain some wonderfully clever ideas and surprising results, not least of which is the rather magical way that the Lichnerowicz-York equation from general relativity magically pops out when you apply Barbour’s ideas to three-metrics modulo diffeomorphisms and volume-preserving (!) conformal transformations.

    *: It’s rather unfair to label this work as being solely due to Barbour; I do so only for the sake of brevity.

  20. Fourier says:

    What is fun is that fourier had this figured out a while ago. Effectively transforming a time series signal into its component time independent modes. All one needs to know is the relative phases…aka initial conditions.

  21. Pingback: Does Time Exist? | Cosmic Variance | My Blog

  22. Mitchell Porter says:

    Christian Ready said

    “I don’t think I’ve ever quite gotten my head around the concept that time is an illusion. Relative to the observer? Of course. Bi-directional? Perhaps. But nonexistent? Ok that has me stumped. Otherwise, there wouldn’t be any change at all, right?”

    Congratulations, you may turn out to be the one sane person in a thread full of amateur metaphysicians.

  23. Joel Rice says:

    Is it possible that Physics has an Algebra Deficit Syndrome, characterized by weird theories, bizarre speculations, and a general malaise regarding whether we can make any sense of the world ? Do the eyes glaze over at any mention of octonions? Partial relief might be provided by A.A.Albert’s Studies in Modern Algebra, and Howard Georgi’s Lie Algebras for Physicists.

  24. Ken says:

    I remember a science fiction story from forty years ago or so, called “Flux”, in which it turned out that time doesn’t exist. The universe, such as it is, is completely random particles, which every now and then happen to fall into a pattern with observers, complete with memories of never-existent prior states. Last Thursdayism writ large, as it were.

    It’s horribly non-disprovable, if you let yourself be bothered by things like that. It could have just happened, as your eyes hit this * asterisk; you remember reading everything before that, but it never really happened. For that matter, you never actually read that first asterisk, or what you are reading now; the universe came into existence when you hit this asterisk *.