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What's Ultimately Possible in Physics?
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Spring 2008
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Previous Contests
What's Ultimately Possible in Physics?
Spring 2009
Special Thanks to Bruce & Astrid McWilliams
read/discuss • winners
The Nature of Time
Spring 2008
read/discuss • winners
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FQXi FORUM
September 2, 2010
CATEGORY:
The Nature of Time Essay Contest
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TOPIC: Time is not the problem. by Olaf Dreyer [refresh]
TOPIC: Time is not the problem. by Olaf Dreyer [refresh]
Essay Abstract
Attempts to quantize general relativity encounter an odd problem. The Hamiltonian that normally generates time evolution vanishes in the case of general relativity as a result of diffeomorphism invariance. The theory seems to be saying that time does not exist. The most obvious feature of our world, namely that time seems to progress and that the world changes accordingly becomes a problem in this presumably fundamental theory. This is called the problem of time. In this essay we argue that this problem is the result of an unphysical idealization. We are caught in this ``problem of time'' trap because we took a wrong turn in the early days of relativity by permanently including a split of geometry and matter into our physical theories. We show that another possibility exists that circumvents the problem of time and also sheds new light on other problems like the cosmological constant problem and the horizon problem in early universe cosmology.
Author Bio
Olaf Dreyer's research focuses on novel approaches to quantum gravity and the foundations of quantum theory. He obtained a Ph.D. in quantum gravity from Pennsylvania State University and he held a postdoctoral position at the Perimeter Institute for Theoretical Physics and a Marie Curie fellowship at Imperial College of Science, Technology, and Medicine. He is currently a postdoctoral fellow at MIT.
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Attempts to quantize general relativity encounter an odd problem. The Hamiltonian that normally generates time evolution vanishes in the case of general relativity as a result of diffeomorphism invariance. The theory seems to be saying that time does not exist. The most obvious feature of our world, namely that time seems to progress and that the world changes accordingly becomes a problem in this presumably fundamental theory. This is called the problem of time. In this essay we argue that this problem is the result of an unphysical idealization. We are caught in this ``problem of time'' trap because we took a wrong turn in the early days of relativity by permanently including a split of geometry and matter into our physical theories. We show that another possibility exists that circumvents the problem of time and also sheds new light on other problems like the cosmological constant problem and the horizon problem in early universe cosmology.
Author Bio
Olaf Dreyer's research focuses on novel approaches to quantum gravity and the foundations of quantum theory. He obtained a Ph.D. in quantum gravity from Pennsylvania State University and he held a postdoctoral position at the Perimeter Institute for Theoretical Physics and a Marie Curie fellowship at Imperial College of Science, Technology, and Medicine. He is currently a postdoctoral fellow at MIT.
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Dear Dr. Dreyer:
I have just read your very interesting essay; and it seems to me that, since your internal relativity recognizes a "Newtonian"-like background time, it would dispense with many problems of time, because time has a definite direction. Each space-time point would be in exactly one hypersurface of simultaneity and each world line would intersect each hypersurface exactly once...
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I have just read your very interesting essay; and it seems to me that, since your internal relativity recognizes a "Newtonian"-like background time, it would dispense with many problems of time, because time has a definite direction. Each space-time point would be in exactly one hypersurface of simultaneity and each world line would intersect each hypersurface exactly once...
view entire post
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Dear Olaf,
There are similarities in our approaches, in fact, a reference to your work was removed only on the last cut in trying to get our essay down to 5000 words :-)
You don't mention it, but your approach would seem to account for Novikov's self-consistency conjecture for GR, identifying paradoxes such as Polchinski's as "the consequence of an unphysical idealization: namely that of geometry without matter." Or does this reflect a misunderstanding of your idea?
Also, I'm wondering if your "pre-causal phase," which is responsible for solving the horizon problem, might somehow be relevant for explaining QM non-locality? Or, does this pre-causal phase only exist at high energies?
Great essay, Olaf. I think I've found another worth my vote!
Mark
post approved
There are similarities in our approaches, in fact, a reference to your work was removed only on the last cut in trying to get our essay down to 5000 words :-)
You don't mention it, but your approach would seem to account for Novikov's self-consistency conjecture for GR, identifying paradoxes such as Polchinski's as "the consequence of an unphysical idealization: namely that of geometry without matter." Or does this reflect a misunderstanding of your idea?
Also, I'm wondering if your "pre-causal phase," which is responsible for solving the horizon problem, might somehow be relevant for explaining QM non-locality? Or, does this pre-causal phase only exist at high energies?
Great essay, Olaf. I think I've found another worth my vote!
Mark
post approved
Hi Olaf,
Great essay. My question is really for both you and Fontini in that you both begin with a pre-geometric base, the rejection of the dualism between geometry and matter and a Lorentzian take on GR (and thus SR). Question one: while you both get out of the problem of time (Wheeler-DeWitt), do you think that the Lorentz interpretation is sufficient to get out of the blockworld (BW)implication of the relativity of simultaneity? That is, do you think the Lorentz interpretation somehow yields a preferred frame at the level of spacetime itself? Of course Wheeler-DeWitt is more radically timeless than the BW of M4, but I'm curious if you are additionally alleging not only to recover GR or M4 from your pre-geometric base but also a preferred frame that negates BW? If so, how does this story go and does the preferred frame map onto the experience of the present moment in some way? Question two: am I right in thinking that at bottom you both have Causality and/or a pre-geometric analogue of a preferred frame? I gather this is the norm, but why isn't this considered cheating? Is it surprising that one recovers SR if one starts with Causality?
Part of the reason I ask these questions is that we also have a pre-geometric base that negates the dualism between geometry and matter but by contrast we begin with a discrete graph theoretic approach {a discrete path integral formalism, though we don't interpret it as path integrals as such} and we recover the entire BW of spacetime. That is, our pre-geometric account isn't dynamical at all (and we assume neither Causality or a preferred frame)and what we recover is the BW. We started with a time-symmetric (acausal and adynamical) interpretation of QM called the relational blockworld and worked backwards to QG so we have a solid story about recovering QM from our pre-geometric base. In any case, I'm hoping you guys will look at our essay (see below) and offer comments as there is much to discuss in our similarities and differences.
Cheers,
Michael
http://fqxi.org/data/essay-contest
-files/Stuckey_Stuckey_Silberstein.pdf
post approved
Great essay. My question is really for both you and Fontini in that you both begin with a pre-geometric base, the rejection of the dualism between geometry and matter and a Lorentzian take on GR (and thus SR). Question one: while you both get out of the problem of time (Wheeler-DeWitt), do you think that the Lorentz interpretation is sufficient to get out of the blockworld (BW)implication of the relativity of simultaneity? That is, do you think the Lorentz interpretation somehow yields a preferred frame at the level of spacetime itself? Of course Wheeler-DeWitt is more radically timeless than the BW of M4, but I'm curious if you are additionally alleging not only to recover GR or M4 from your pre-geometric base but also a preferred frame that negates BW? If so, how does this story go and does the preferred frame map onto the experience of the present moment in some way? Question two: am I right in thinking that at bottom you both have Causality and/or a pre-geometric analogue of a preferred frame? I gather this is the norm, but why isn't this considered cheating? Is it surprising that one recovers SR if one starts with Causality?
Part of the reason I ask these questions is that we also have a pre-geometric base that negates the dualism between geometry and matter but by contrast we begin with a discrete graph theoretic approach {a discrete path integral formalism, though we don't interpret it as path integrals as such} and we recover the entire BW of spacetime. That is, our pre-geometric account isn't dynamical at all (and we assume neither Causality or a preferred frame)and what we recover is the BW. We started with a time-symmetric (acausal and adynamical) interpretation of QM called the relational blockworld and worked backwards to QG so we have a solid story about recovering QM from our pre-geometric base. In any case, I'm hoping you guys will look at our essay (see below) and offer comments as there is much to discuss in our similarities and differences.
Cheers,
Michael
http://fqxi.org/data/essay-contest
-files/Stuckey_Stuckey_Silberstein.pdf
post approved
I do agree with you about the 'split' between Geometry and real Universe that drives in my opinion to build a fake Universe with computers; 'Superstring theory' is the best example of this virtual world. I am pointing this in my own essay ('Square Wheels or Real Dynamics?').
BUT, contrarily to you I would not say that the Theory does seem to abolish Time. This theory is either abolishing Time OR Space: one can make it say what one want. Due to my French culture, it is more creating a fake conventional Time than abolishing it. I mean that Einstein's theories are grounding a kind of Time-religion.
My statement is therefore that the split is in Quanta Physics as much as in Einstein's theory. The 'Wave idea' in particle's Physics is 'the theory seen as part of reality'. 'Dualism' and paradoxes are coming from this.
(One can notice that even on a theoretical level, 'General Relativity' of Einstein was destroyed by H. Poincaré himself who does explain that there is a split between the conclusion of GR and its postulate.)
post approved
BUT, contrarily to you I would not say that the Theory does seem to abolish Time. This theory is either abolishing Time OR Space: one can make it say what one want. Due to my French culture, it is more creating a fake conventional Time than abolishing it. I mean that Einstein's theories are grounding a kind of Time-religion.
My statement is therefore that the split is in Quanta Physics as much as in Einstein's theory. The 'Wave idea' in particle's Physics is 'the theory seen as part of reality'. 'Dualism' and paradoxes are coming from this.
(One can notice that even on a theoretical level, 'General Relativity' of Einstein was destroyed by H. Poincaré himself who does explain that there is a split between the conclusion of GR and its postulate.)
post approved
I enjoyed your essay very much. One quibble, if geometry reacts to matter that does not necessarily mean it "evolved in the absence of matter". Geometry could have evolved from matter AND react to matter. Think of evolution. The environment affects the genome which then affects the environment.
By geometry do you mean space-time?
Thank-you,
Sandy
post approved
By geometry do you mean space-time?
Thank-you,
Sandy
post approved
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