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. 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. 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