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From time to timescape – einstein’s unfinished revolution?

  1. Dec 24, 2009 #1


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    In today's Physics ArXiv:


    Dark Energy as simply a mis-identification of gravitational energy gradients and the resulting variance in clock rates?

    David Wiltshire's Abstract:
  2. jcsd
  3. Dec 25, 2009 #2
    A fox among the Christmas Turkeys, indeed --- if it were true. Perhaps it is. I'm not competent to judge. But Wiltshire's claim that differently situated observers would assign widely different ages to the universe has an echo even in special relativity, which teaches us that there is no absolute measure of duration or absolute notion of simultaneity or concept of "now'.

    Just imagine not a twin paradox, but say a multiplet paradox, in which many siblings follow very different worldlines through spacetime before reuniting for Christmas festivities. They would then have different physical ages, despite their common origin. There is no such thing as a universally experienced measure of age --- unless it is one's wrinkle count.

    If Wiltshire is correct, would observers differently situated in the universe (say void dwellers and galaxy dwellers) nevertheless all measure the same Z for the Cosmic Microwave Background? and if so, would their assignment of a common age to the universe using a common scheme (say the Lambda CDM model) then be as misleading as the assignment by members of the the multiplet siblings of a common age to them, despite their diversity of wrinkle counts? Wiltshire's arguments suggest to me that the answer might be "yes".
  4. Dec 25, 2009 #3


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    First it seems you have misunderstood the twin paradox.

    The paradox is not that the twins on meeting up find they have different ages, as you seem to suggest, but that each might think that it is they who are the eldest.

    The paradox in SR is resolved by determining which of the twins had not been on an inertial trajectory through space-time. It is that twin uniquely who would be of the younger age.

    Last edited: Dec 25, 2009
  5. Dec 25, 2009 #4
    I suspect you are considering the particular, instead of the general case --- but I'm not sure. Perhaps you could elaborate a bit more? I'm under the impression that observer-measured durations and their differences depend in general on the integrated proper time that elapses along any closed loop of worldline followed by an observer, not just on who follows a non-inertial path and who doesn't. Is it the sign of the difference, rather than its magnitude that you are talking about?
  6. Dec 25, 2009 #5

    George Jones

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    Let A and B timelike related events with B in the future of A.

    Special relativity. Of all the observer worldlines running from A to B, the worldline of the unique intertial observer who experiences both A and B has the greatest integrated proper time.

    General relativity. There is not necessarily a unique inertial (freely falling) worldline joining A and B, and it is possible for the integrated proper time of an accelerated observer who experiences A and B to be greater than the integrated proper time of an inertial observer who experiences A and B. See


    I started this post with
    and I wrote recently in another related post
    but I have not written these promised posts.

    I haven't read Wiltshire's paper (I hope to read it soon.), but I don't think these counter-intuitive GR results play a role.
  7. Dec 25, 2009 #6


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    Sorry, if I read
    I've had enough.
    Wiltshire may or may not have a point, he won't get (me as) an audience as long as he's earning ~30 crackpot points in the abstract alone.
  8. Dec 25, 2009 #7
    Thanks, George. Your statement in the earlier post you refer to here, namely:
    is a further clarification of my impression that:
    . Time is indeed strange, and it seems to me that Wiltshire's further (i.e. beyond Einstein's) exploration of this strangeness is worth undertaking. Whether he is correct or not is another matter......
  9. Dec 26, 2009 #8


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    He's not a crackpot. He's a former student of Hawking and well respected. I heard him give his first paper about five years ago and the latest version just the other week. This year he has finally been getting a lot of traction - plenary in Paris, etc.

    It may still be a wrong explanation. Dark energy may be true. But occam's razor says the simpler case must be ruled out. And Wiltshire is now getting to the level of calculation where things look testable.
  10. Dec 26, 2009 #9
    That doesn't disqualify him from being a crackpot. One reason that I have a lot of tolerance to amateur crackpots is that I've learned to tolerate the huge number of professional crackpots in the field.

    On the other hand, being a crackpot isn't necessarily a bad thing. The only difference between a genius and a lunatic is that the genius can turn off the voices when he needs to.
  11. Dec 26, 2009 #10


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    Erm, any references to support that? It's not really fair to either geniuses or lunatics, even if you say it in jest.

    Personally, I think Wiltshire is doing a clever thing. And of course I am influenced by spending time with him to find out what he is about.

    He started off responding to dark energy. He realised it might be just observational error due to our local frame of reference being possible underdense.

    Then regardless of whether this is true or not, he has moved on to a more general issue. The fact that GR cosmology has made a simplifying assumption about the metric, that everything is flat, smooth, homogeneous, isotropic, and is not thus an accurate model of the reality.

    As he says...

    So you have a relativistic background in which there is no average frame of reference in fact. Even the CMB probably doesn't give you a universal measure of time.

    So how do you do the calculations for the equation of state if there is a basic lumpiness to things that creates a cosmic froth of relativistic effect curving the background itself?

    Wiltshire was saying this lumpiness is suggested by observational evidence of fractal matter distribution, which in turn is a likely result of the sound horizon in early big bang. This is fairly recent motivation for actually moving the calculations to another level of relativistic precision.

    I asked him why it hadn't been done already. He said just because the calculations are really, really, difficult. You would have to have a lot of motivation to take the project on. He has had to take the project on because people pointed out the lack of full-working out in his early papers.

    As usual, genius is in fact 90% perspiration. And cranks are the people who don't learn from their critics.
  12. Dec 26, 2009 #11


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    What I recall (correct me if I am wrong) is that Gary Gibbons was a PhD student of Hawking and that Wiltshire had Gibbons for advisor. Which doesn't contradict what you said. Just that in terms of PhD advisor, Wiltshire is Hawking's "grand-student".

    I remember reading Wiltshire's early papers about an alternative explanation of accelerated expansion---coming from largescale unevenness in density. Back in 2005 or so, I think.
    I've always thought of his line as worth pursuing, but so far not convincing and not (yet at least) appropriate to make a big fuss about.

    Kea, a PF member who posted a lot here in around 2005-2006, had a high opinion of Wiltshire. She was a kiwi PhD student/postdoc.

    I think twofish was (as you suspected) speaking in jest. Jovial jesting like that is hard to balance so that it is perfectly fair. I thought what he said was pretty funny, enjoyed it, although I completely disagree with the characterization "crackpot"
  13. Dec 26, 2009 #12


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    That is quite true. Universe time is only approximately definable, inasmuch as the FRW model fits (which it doesn't, exactly).

    Time is a delicious mystery.

    By coincidence it was Carlo Rovelli (back in 2003) who pointed out to me that we have no universal measure of time. He said something like "what about people deep in massive galaxies" compared with other people in less dense places. He asked if I could see how to put all those times together to get a universal standard time. A gentle guy and a good teacher.

    I think we have to agree with a lot of what David Wiltshire says. (And respect his courage for pursuing a longshot.)

    But I don't think we have to deny the existence of a positive cosmological constant, or the practical value of the CMB as a reference, or the remote (as yet unrealized) possibility of defining a universal time. We may yet know and understand so much more than we do today.
  14. Dec 27, 2009 #13
    Personal experience. Every theorist that I know (including myself) has some crazy, insane, long shot idea that they secretly think is the key to understanding the universe. The difference between productive physicists and the less productive one's, is that the more productive ones will keep the craziness under control, share their really weird ideas over drinks, but refrain from publishing papers in which you announce that you've solved the mysteries of the universe. From time to time, a theoretical physicist will lose it and either formally or informally say "YOU ARE ALL IDIOTS!!!! I KNOW WHAT IS GOING ON HERE!!!!" That usually doesn't provoke a good reaction (even if from time to time it happens to be true).

    The other thing is that just like there is a very strong correlation between bipolar disorder and novelists, the number of theoretical physicists that are under treatment for some mental condition or have some close family member who is, seems to be much larger than the general population. What I mean by "being able to turn off the voices" is that there is the "I HAVE FOUND THE SECRET OF THE UNIVERSE" part of doing theoretical physics, and then then "well..... maybe not....." part. People that end up being productive are able to do the second phase.

    Which is quite widely realized.

    You do a back of the envelope calculation that argues that GR effects aren't going to be that huge in calculating the EOS.

    Also GR calculations *are* hard to do. There is a community of people that believes that redshifts are completely due to tired light and GR effects and those people *are* considered crackpots by most observational cosmologists. One thing that Wiltshire has to be careful is to not get lumped in with that group of people unless he really has some smoking gun.

    One thing that can happen is that one professional crackpot can discredit an entire field of inquiry in which case things get thrown out that shouldn't be. Using GR symmetry arguments to propose basic changes in interpreting cosmological data gets you close enough so you have to be a little worried about how to phrase your papers.
    Last edited: Dec 27, 2009
  15. Dec 27, 2009 #14
    The thing that I'm interested in is whether Whitshire is proposing that general relativity as currently used in the standard model is wrong. If he is then it should be possible to take his proposed extensions to GR and then back translate them into an f(R) model in much the same way that the 3+1 membrane paradigm allows you to apply newtonian dynamics to black hole accretion disk models, and I *think* that Whitshire is basically doing the same thing.
  16. Dec 27, 2009 #15


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    Just for the record: I didn't say that he is a crackpot. I just said that I'm not going to read a paper with "paradigm shift" and "Einstein wrong" in the abstract.
    If there will really be a paradigm shift, it will come with a paper called "On a Heuristic Point of View Concerning the Production and Transformation of Light" or similar. Not everyone can afford understatement, I'll have a look at those who can.
  17. Dec 27, 2009 #16


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    Yeah, next thing you know he will be talking about discovering "the mind of God".

    But perhaps if you stopped at the abstract, you missed the note that puts things in a little more context.

  18. Dec 27, 2009 #17
    What about an informed answer to this question, instead of discussions of Wiltshire's scientific status?

    It's not as if dark energy is such a well understood and experimentally confirmed part of physics as to preclude further suggestions!
  19. Dec 29, 2009 #18
    I would say the only difference between a genius and a lunatic is that eventually everyone agrees with the genius.

    The fear and hatred that people express towards the non-canonical is just as high as the Catholic Churches fear and hate of Galileo. I think we have discovered a truth about human nature. People hate new ideas.
  20. Dec 29, 2009 #19
    Or more generally there are two kinds of physicists 1) those whose status and self worth is tied to their mastery of an existing canon of theory and experimental data and who feel threatened by their current view being called into question and 2) those who enjoy learning and discovery and ideas (Ars Gratia Artis) an example would be Feynman.

    Yes there are plenty of crazy people with crazy ideas that we could waste our whole lives reading and so we must try to filter the garbage from the gems. But the hate is a psychological problem of the hater. If you have some rational for filtering something tell me about it but I have no interest in hearing your hate or using your hate as a filter.
  21. Dec 29, 2009 #20


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    I second that motion.

    I think we can accept Wiltshire is a credible academic. I've met enough geniuses and madmen to tell the difference. I wouldn't describe Wiltshire as either. But he seems to be doing exactly the kind of thing science is suppose to do - looking at the simpler explanation for surprising findings.
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