A Conversation on the Existence of Time

By Sean Carroll | November 19, 2009 1:27 pm

You know, other people talk a lot about time, too — it’s not just me. Here’s a great video from Nature, featuring a conversation between David Gross and Itzhak Fouxon about the existence of time. (Via Sarah Kavassalis.) Itzhak plays the role of the starry-eyed young researcher — he opens the video by telling us how he originally went into physics to impress girls, although apparently he has stuck with it for other reasons. Gross, of course, shared a Nobel Prize for asymptotic freedom, and has become one of the most influential string theorists around. David plays the role of the avuncular elder statesman (I’ve seen him be somewhat more acerbic in his criticisms) — but he’s one of the smartest people in physics, and his admonitions are well worth listening to. He gives some practical advice, but also advises young people to think big.

Unfortunately the video doesn’t seem to be embeddable, but you can go to the video page and click on the “David Gross” entry. (The others are good, too!)


You all know my perspective here — time probably exists, and we should try to understand it rather than replace it. But I’ll agree with David — let’s not ignore more “practical” problems, but not be afraid to tackle the big ideas!

CATEGORIZED UNDER: Advice, Science, Time
  • http://badphysics.wordpress.com/ S.C. Kavassalis

    I really liked this conversation – not only because I appreciated the content of their discussion, but I really enjoyed how representative it was of the class of conversations between the senior theorist, with this great body of work to back up his name, and the very ambitious young theorist, who has all these ides but hasn’t written up “the equations” to support them with yet.

    I think Fouxon’s approach, of trying to start with the most general assumptions as possible, for the global structure of the universe, should be the way all cosmology is done. But perhaps that’s also my youthful impracticality talking.

  • BAHAHAHA!!!!!

    I get it! Don’t quit your day job!

  • KiwiDamien

    I thought David was actually pretty good here, and did a lot for getting rid of the notion of string theory as an establishment that automatically closes out a theory that is not string theory.

    Having said that, it was frustrating to watch. Fouxon kept presenting ideas so vague that it was not clear what he even meant by them — for example talking about energy in the absence of time. It is not that he does not have equations, but that he does not even have a clear idea of what he is trying to achieve and what sort of framework his theory would accomplish. One that was not picked up on by Gross (or at least not commented on) was the idea that “space was first” and then it relaxed and you could introduce time.

    Without time, how could something be first? By “introducing time” does Fouxon mean that a collective object starts to behave in a manner resembling a clock, or does he literally mean adding in an extra dimension by hand and then “matching” at an appropriate scale, or something else altogether? There was not even something as definite and cohesive as mentioning what he thought was responsible for the appearance of time or what evidence or principle would be supported by eliminating time.

    It simply seems like this guy has read about Wheeler’s quantum foam / causal sets / discretized spacetime in popular accounts and thought it sounds cool, and asked David Gross about it. The real questions are how did he manage to get David Gross to talk to him for so long, and why someone thought this was “physics in action” and made a video about it.

  • Sebi

    Itzhad should have asked David why he continues to collect $300K/year when starry-eyed students at his university are faced with a 32% tuition increase and a post-graduate hiring freeze.

  • http://orbum.net/mark Mark

    One of the telling things was the student suggested it may be time to bring philosophy back more into physics, yet Gross was saying that he must see the equations from the student about his ideas.

    I’m not certain what Gross meant when he said that physicists had “higher standards” than philosophers – that doesn’t seem to have any meaning, and perhaps that is a higher standard… ? What I suspect he meant was the physicists require measurable evidence, which is of course, not mathematics alone, and that philosophers do not require measurable evidence. The thing is, a philosopher must take into account measurable evidence when it is available, and can consider the maths, even though it is not require, when neither are available, for speculation.

    And this leaves us with the question, does the student consider himself more a philosopher or a physicist?

  • http://eternal-cartesian.blogspot.com/ Cartesian

    For Mark 5 : I think that philosophy should be considered as something global, what is going with the meaning of PhD, which is in order to be doctor of a part of philosophy.

  • Michael

    I still believe that ‘time’ is a human construct. We invented it because it’s convenient and a great way to sort out events, etc. Sorta like the Bohr model of the atom — not real, doesn’t look or act anything like a real atom, but convenient nonetheless.

  • hackenkaus

    Fouxon comes off as almost Bogdanov-like in this video, spouting off vague poorly formed thoughts that make less sense the more you think about them. In physics, if you don’t got equations, you don’t got nuthin (paraphrasing Feynman I believe). I was surprised when I googled him and found he actually has a legitimate publication record. This is why I don’t like physics as entertainment for the masses.

    And don’t begrudge Gross his modest $300K per year; there are thousands of U of C empoyees who make that much or more, and very few have Nobels. There are freaking nurses who make over $200K / yr.

  • A.H

    >it’s not just me.

    Indeed. Back during that FQXi contest I was pretty stunned at the sheer number of people with vested interest in the matter. It’s not just the intuitive concern over the issue, but the connection to so many other different subjects.

    I recall George Ellis’ paper “The Flow of Time” being very convincing in particular. The judges were clearly impressed too, but it would have been nice to know what the other researchers (and maybe Prof. Gross) thought of it. It’s very hard to laugh in the face of quantum decoherence.

  • Wilburrr

    What is time? That’s about as difficult as asking what consciousness is. Describing what time is almost falls into the realm of meta-physics. But time can be represented. Think of a simple wave. It flows one way, forward. Time dilation experiments have shown that clocks lose time flying east and gain time flying west. Whether gaining or losing time, it only flows forward. You can propel yourself ahead of the wave or resist it by running up the wave, but the wave pushes you forward either way. Our time really isn’t ours. It’s the earth’s time that we travel along. As it moves, we move with it.

  • Just Learning

    The problems encountered with doing away with time run much deeper; it not only undermines physics, but undermines some of our notions of what a variable actually is.

    A good question to ask is: how can one define a time independent variable without defining time?

    Math is highly vulnerable to timelessness; and even our use of language. Just imagine a world without verbs. What do we mean by action?

    These are very difficult questions; and require a very rigorous framework to even be approached.


  • Angus McPresley

    I guess this is the right thread to say that I was at your Melbourne public lecture on the arrow of time the other night, and I thought your response to the question about whether time might be an illusion was great…

  • Anti Vigilante

    Time does not exist.
    Time is not sequence.
    Sequence has always existed.
    Sequence is spatial.
    Space is the path followed.
    Space inside space inside space is madness.
    Time is madness.

    Time is the comparison of spatial sequences which happen to coincide when taken as a total larger system.

    Time is an illusion of language, sequence, and repetition which is necessary for intelligence to exist.

  • Just Learning

    Sequence is spatial.

    Unfortunately, we also understand position in space as the conjugate of momentum…momentum is a concept dependent on the definition of time. I am stuck back in the trap of time.

  • http://www.SdogV.com SdogV

    Without mass light does not exist. Without time, mass does not exist.
    In short, light needs mass and mass needs time forboth to have a verifiable existence;.

  • Just Learning

    Without mass light does not exist.

    Not sure what is meant by this. Light is massless. Mathematically, one way to approach the problem is to describe a system with massive particles and then allow the mass to go to zero, which then produces an a system with massless photons; but that doesn’t change the fact that photons are massless.

  • Fouxon

    Maybe some of you will be interested to have a look at


    where a timeless framework for the universe is proposed.


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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] cosmicvariance.com .


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