Cosmology, Quantum Mechanics & Consciousness Message Board › The universe is not a computer

The universe is not a computer

A former member
Post #: 192
Following up on an article in New Scientist I’ve found an interesting essay about fundamentals called “The universe is not a computer”. This essay can be found at http://arxiv.org/pdf/...­. The author is Ken Wharton, a quantum physicist. He comments on the puzzles of quantum physics, including the “...ridiculously impossible ‘collapse’, when all the built-up uncertainty suddenly emerges into reality.” His argument is that our difficulties with QM are down to a hidden anthropocentric bias. Science has made progress when such biases have been identified and removed. Earth is not at the centre of the solar system. The condition of Schrodinger’s cat does not depend on a human observer, etc. Wharton proposes an addition to this list: the universe does not behave in the way that our models, theories, machines and computers behave. All those things are our own creation, basically along the lines of: here is a particular physical system or process; here is how it starts off, we know the theory so we can work out how it will end after a certain time. Except that in QM we settle for less and just work out the probabilities of how it will end. To paraphrase Wharton, why suppose that the universe works in ways that our human thinking can easily grasp?

He offers a novel suggestion. At the heart of all physics is a mathematical principle called ‘least action’. This principle can be used to derive Newton’s laws of motion. For example things tend to travel in straight lines in the absence of net force because that is the path of least distance between any two points. Light seems to do the same but it will diffract round corners because it is actually following a path of least time. Just about all of physics can be derived from least action, subject to finding the right ‘action’ quantity to be minimised. In QM the principle underlies Feynman’s path integral approach. Least action is usually assumed to be a mathematical trick for getting correct answers; it doesn’t come with any underlying explanation of physics to explain why the principle works. Until now, perhaps. Wharton proposes that the universe actually works on a least action principle. The closing words of his full paper are as follows: “It is these models, the balance of the evidence suggests, that have a chance of representing how our universe really works. Not as we humans solve problems, not as a computer, but as something far grander.”

This idea is not at present the solution to anything; it’s merely a promising suggestion for a whole new programme of fundamental physics research. But I like it. It reinforces another important but usually ignored message about the significance of time-symmetry in most of physics. In time-symmetric QM the superposition state of a system (say an electron) depends on both initial state (eg location where it was observed) and final state (location where it will be observed). Note the analogy with a straight line trajectory - the shortest path between where an object was and where it will be! Watch out - some cherished ideas about time, causality and much else may be up for review!



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