Quantum science (Introduction)

by George Jelliss , Crewe, Sunday, September 13, 2009, 11:14 (5346 days ago) @ xeno6696

Quantum Gods (QG) seems to be aimed at the American market more than the British, since it begins with a chapter on "Belief and Nonbelief in America" which harks back to the Deist views of the founding fathers, and looks at the statistical results of the 2008 Pew survey of beliefs. Chapter 2 is a response to the movie "What the Bleep Do We Know" which was popular over there but has made no waves over here that I've noticed. In the next two chapters he goes back to Fritjof Capra's 1975 "The Tao of Physics", and the Maharishi's 1967 "Transcendental Meditation" movement. Then he gets down to some physics.-The Comprehensible Cosmos (CC) is purely about physics in broad terms (the subtitle is "Where Do the Laws of Physics Come From?"). His answer is that a lot of the laws follow from "point-of-view invariance". For instance the laws of conservation of energy, and of linear and angular momentum follow from the assumption that the laws are invariant to changes in time, distance, and angle of the observer's frame of reference. This was proved by Emmy Noether in 1915. Since experiment shows these to be true, then the assumption is justified.-What interests me most are his views about the nature of time and the way this affects our understanding of quantum physics. Some extracts: -CC p35: "Folowing Einstein we define time simply as what is measured on a clock. Whatever its construction, a clock will provide a series of ticks and a counter of those ticks. Note that in our operational view, time is fundamentally discrete." 
CC p37: "Since 1983, distance in science is no longer treated as a quantity that is independent of time. In fact, distance is now officially defined in terms of time ///: the time it takes light to travel between two points in a vacuum. -CC p100; Most physicists prefer to adopt a specific time direction, even when none is called for by theory or experiment. In that case, they must introduce antiparticles. However, a more parsimonious view, which is experimentally indistinguishable from the conventional one, is to interpret antiparticles as particles moving backwards in time, that is, opposite the conventional direction."-CC p101 and QG p.205: He gives the example of a "Feynman space-time zigzag" in which one electron moves forward in time scatters off a photon, moves backward in time, scatters off another photon, and moves forward in time again. The conventional interpretation of this requires three particles (two different electrons and a positron); in the initial position a positron-second electron pair appears from the vacuum, and later the positron-first electron pair annihilate each other. -As a devout Ockhamist the economy of this interpretation appeals to me strongly.-CC p119: "The second law of thermodynamics says that the entropy of an isolated system must stay the same or increase with time. But how do we define the direction of time? All the equations of physics, except for the second law, work in either time direction. /// increasing entropy can in fact be regarded as defining /// the arrow of time. Thus we have another "law" of physics that turns out to be nothing more than a definition. However /// the second law is a statistical statement that is meaningful only when the number of particles is large. This implies that the arrow of time only applies in that context. In systems with few particles, the entropy will fluctuate substantially from its equilibrium value and an arrow of time becomes impossible to define." -CC. p 120: "In a previous book Timeless Reality ... I discussed in detail the implications of the apparent time-reflection symmetry of the fundamental laws of physics. In particular I showed that many, if not all, of the so-called paradoxes of quantum mechanics can be understood as a consequence of forcing the familiar time direction of ordinary experience on the description of quantum events."-CC. p186; "The usual objection that is raised against motion backward in conventional time is the so-called grandfather paradox. If one could travel back in time, he could kill his own grandfather. However, it can be shown that this paradox does not hold at the quantum level, where all grandfathers are indistinguishable." (!!) -CC p120: In Timeless Reality I showed that time reversal makes it possible to reify many of the features of modern quantum and particle physics. For example the multiple particle paths in the Feynman path integral formulation of quantum mechanics can be pictured as actually occurring in a single event /// as the particle zigzags in space-time." -I find this more appealing to my Ockhamist instinct than the Multiple Universes version. It seems I need to buy another Stenger book!

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GPJ