Does Time Exist?

By Sean Carroll | October 25, 2011 8:51 am

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.

CATEGORIZED UNDER: Philosophy, Science, Time, Top Posts
  • Dave

    Video removed by user =(

  • Peter

    The video seems to be down :-(

  • Bahador

    “This video has been removed by the user” :(

  • Sean

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

  • thanosk

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

  • mma

    link is broken, video removed by user.

  • ts

    Video doesn’t work beyond 3:08

  • Henry

    “This video has been removed by the user.”

    Any chance we can get a fixed link?

    Edit: Aaaaand nevermind.

  • chabuhi

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

  • Pietr Hitzig

    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.

  • Sean

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

  • Stephen Crowley

    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.

  • Donal Henry
  • Georg

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

  • Ed Minchau

    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.

  • Mike Empyema

    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.

  • Eunoia

    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 😉

    • Sean

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

  • Christian Ready

    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?

  • KernelMethod

    “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.

  • Fourier

    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.

  • Pingback: Does Time Exist? | Cosmic Variance | My Blog()

  • Mitchell Porter

    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.

  • Joel Rice

    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.

  • Ken

    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 *.

  • John Merryman

    I think the problem is that we intuitively think of time as the present “moving” from past to future and try to model it as some form of vector, or flow. The physical process is a changing configuration of what exists. It’s the future becoming the past. The present doesn’t move, but the ephemeral events which come and go. That way, it’s an effect of motion, similar to temperature. Rate of change, level of activity. This way, there can be both variable clock rates and a real dynamic present.

  • Ronald McCoy

    How wonderful! Thankyou for sharing this.

    Ronald McCoy

  • Pingback: A Cornucopia of Time Talks | Cosmic Variance | Discover Magazine()

  • Stephen

    I see a problem in the “best matching of configuration spaces” idea, it assumes a measure where one cannot exist (assuming analysity of the functions on the configuration spaces). Additionally, the computation of “best matching”, even on a discrete configuration space, is an NP-Complete problem. What is doing the computation such that solutions obtain? One cannot assume the solution to simply exist prior to the possible implementation of the computation of it and yet have causal efficacy!

  • Matthew Marsden

    I have written an entire book draft on the subject of time, or rather Timelessness, (‘A Brief History of Timelessness’) some of which you can see on my website (along with 4-5 videos of talks I have given).

    My opinion, which I think can be shown to be logically complete, is that rather than ask the leading questions ‘Does Time exist?’, or even ‘What is Time?’, we should first ask ‘What do we actually directly observe?’ in the world around us, and then see what we discover.

    It seems to me that what we actually directly observe,in simple terms, is that objects can exist, and these objects can move, and interact.

    If we then ask ‘are objects just existing, moving and interacting enough to explain ALL that we (mistakenly) attribute to the existence of an extra, and mysterious thing called Time?’ I believe the answer is a very definite yes!

    In particular ‘things just existing and interacting’ is enough to the changing and accumulating contents of our minds (our memories), and the clearly evolved state of objects in the world around us (tree growth rings,fossils etc). Critically while we assume these things prove the ‘existence’ of ‘The Past’, they can be shown to only actually prove that matter can exist and interact ‘now’ so to speak.

    If you read Einstein’s Relativity (Routledge classics) meticulously you can see he at no point actually proves the existence of a ‘Future’ or of ‘The past’ or of a thing called Time flowing between them.

    Einstein’s first mention of Time (section 3) is ‘The purpose of mechanics is to describe how bodies change their position in space with Time’. In fact in mechanics we might compare the motion of one moving object (eg a falling stone) with another moving object, eg a steadily rotating hand on a numbered dial. Both these things prove that objects can exist, move, and be compared to each other. But neither prove that as things move another thing called ‘Time’ also exists and flow from a ‘future’, ‘through’ the Present and into a ‘past’ – or that ‘durations’ or ‘intervals’ of ‘time’ exist in anyway.

    Einstein’s use of the word clock is unintentionally misleading because motorised rotating hands called clocks ‘suggest’ the existence and flow of a thing called time, but don’t prove it.

    Time Dilation – In Special Relativity Einstein does prove that moving objects will run slower than our intuition might suggest – but he does not prove that there is a thing called time – which is slowed – and that the slowing of ‘time’ makes ‘clocks’ etc run slow.

    eg Einstein does not show that a photon trapped and oscillating between two mirrors (a light ‘clock’) heads into or proves the existence of a ‘temporal’ future, or leaves a ‘Temporal’ past behind as it moves, or reveals the ‘passage’ of time.

    So, in my opinion, everything is just as it is constantly directly observed to be. Things exist and move ‘now’ and there is no ‘temporal past’ created anywhere, by any ‘thing’ or ‘stored’ or ‘existing anywhere. (‘Events’ are constantly happening, but they are ‘just’ happening and don’t ‘happen in time’ etc)

    (IMO) Mr Barbour’s ideas may stem from assuming time exists in some way, while also logical realising (IMO correctly) that it does not, and then trying to prove timelessness in terms of time.

    Therefore, amazing and complex as the universe clearly is, it seems to me the idea of ‘Time’ existing other than as a useful tool or notion can be systematically proven to be unfounded. So therefore the universe is ‘Timeless’ (to use a redundant word).
    This may seem to simplistic to be true – but that may well be how Einstein’s ‘Persistent illusion’ hides in plane sight.
    (Happy to answer any questions)

    Matthew Marsden

  • matthew marsden

    sorry – missed word – para 5

    “In particular ‘things just existing and interacting’ is enough to the changing and accumulating contents of our minds ”

    should be

    “In particular ‘things just existing and interacting’ is enough to EXPLAIN the changing and accumulating contents of our minds ”

  • Steve

    Time is not linear. We just live it that way ‘here’, and ‘now’…

  • matthew marsden

    Wise words Steve,
    I wrote a piece on just that, essentially saying

    If as events happen they are ‘recorded’ (‘stored’ or how ever we might phrase it) in a ‘temporal past’ – then- ‘as events happen, an order IS created and stored’.


    If as events happen, they are not recorded in any (temporal) way , anywhere, then that temporal record is not created and does not ‘actually’ exist. And if there ‘is’ no temporal order, then there is no temporal order.

    (Here’s a talk I did on it)


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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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