The results are in for the Foundational Questions Institute essay competition on “The Nature of Time,” which we discussed here. And the winners are:
First Juried Prize:
Julian Barbour on “The Nature of Time”
The jury panel admired this essay for its crystal-clear and engaging presentation of a problem in classical dynamics, namely to find a measure for duration or the size of a time interval. The paper argues lucidly, and in a historically well-informed manner, that an appropriate choice for such a measure is not to be found in Newton’s pre-existing absolute notion of time, but rather emerges, in the form of ephemeris time, from the observable motions and the assumption of energy conservation. The paper also suggests how this emergence of duration might be relevant to problems in quantum gravity.
Second Juried Prizes:
(1) Claus Kiefer on “Does Time Exist in Quantum Gravity?”
A fundamental problem in quantum gravity is that the “Wheeler-DeWitt Equation,” probably our most reliable equation of quantum gravity, does not refer to or even suggest anything like time or evolution. In this context time must emerge in the form of relations between a given system and some other system that may be considered a clock. Kiefer beautifully reviews this problem, and argues how, via quantum “decoherence,” time as described by the usual Schroedinger equation in quantum mechanics can emerge from this timeless substratum, via entanglement between physical systems within space, and the spatial metric that controls motion.
(2) Sean Carroll on “What if Time Really Exists?”
Drawing on recent developments in string theory, Carroll impressed the panel with an exciting account of how a gravitating spacetime might in fact be just a holographic approximation to a more fundamental non-gravitating theory for which “time really exists.” Contemplating the difficulties raised by strange recurrences in an everlasting universe, he argues for a strong condition on the set of allowed quantum states that would disallow such repetitions. Carroll closes by attempting to reconcile this picture with recent observations that indicate that the expansion of the universe is accelerating, with surprising results.
Tied for second is not at all bad, considering the number of interesting entries. There are more prizes, actually, as there are “community” awards as well as “juried” prizes, so check those out as well. It’s pretty amusing that the top three essays all attack, in one way or another, whether or not the subject of the competition actually exists. (I was in favor, the others were more skeptical.)
Besides the essays themselves, I very much appreciate the huge amount of work it must have been for the various judges to read through all of them and make hard decisions. Thanks to the FQXi for sponsoring the contest, and thanks to all the judges for doing a great job!
It seems amazing that none of the authors mentioned quantum interference in the time domain. These are actual experiments demonstrating the existence of time in the same way as the classic double slit experiement demonstrates the existence of space.
Horwitz, L.P. (2005) On the significance of a recent experiment demonstrating quantum interference in time. http://arxiv.org/abs/quant-ph/0507044
“I comment on the interpretation of a recent experiment showing quantum interference in time. It is pointed out that the standard nonrelativistic quantum theory, used by the authors in their analysis, cannot account for the results found, and therefore that this experiment has fundamental importance beyond the technical advances it represents. Some theoretical structures which consider the time as an observable, and thus could, in principle, have the required coherence in time, are discussed briefly, and the application of Floquet theory and the manifestly covariant quantum theory of Stueckelberg are treated in some detail. In particular, the latter is shown to account for the results in a simple and consistent way. ”
The authors also failed to take much note of the “extended present”
See Time and conscious experience
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