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Quantum Mechanics and Determinism

“We may regard the present state of the universe as the effect of its past and the cause of its future. An intellect which at any given moment knew all of the forces that animate nature and the mutual positions of the beings that compose it, if this intellect were vast enough to submit the data to analysis, could condense into a single formula the movement of the greatest bodies of the universe and that of the lightest atom; for such an intellect nothing could be uncertain and the future just like the past would be present before its eyes.”
— Marquis Pierre Simon de Laplace
LaPlace’s Demon

This thought experiment made perfect sense in the days of classical mechanics but does it make sense in terms of quantum mechanics?

What we have now is determined probability as opposed to determinism.
Even if we can’t make reliable predictions about individual events, we can observe the patterns formed by multiple events.
For example, patterns in quantum tunneling are reliable enough that we can make a scanning tunneling electron microscope that works.

So if we suppose we individually have some measure of free will does this mean that collectively we are determined?

Is the universe any less absolutely determined just because it cannot be observed with complete precision?

If we assumed a ‘demon’ with knowledge that exceeded the maximum precision allowed by Heisenberg’s uncertainty principle would we be breaking the laws of physics?
Indeed, is absolute zero a fundamentally impossible temperature precisely because particles without motion would be precisely observable?
Or if we reached absolute zero, would particles remain in motion to uphold uncertainty and the flow of time?

2 responses to “Quantum Mechanics and Determinism

  1. anonymous July 12, 2012 at 11:17 pm

    Even in a classical world LaPlace is wrong. You can’t measure with infinite precision. So over time your predictions would diverge from reality. The chaos guys in the 50s and 60s went over this already.

  2. Giovanni Dannato July 13, 2012 at 2:50 am

    Yeah, any margin of error whatsoever snowballs the ‘demon’ must be perfectly omniscient for it to work.

    It invites us to wonder though if the universe isn’t determined just because we can’t measure it,
    After all if probabilities are predictable enough to be useful, doesn’t this tell us that there is perhaps something fundamentally orderly going on at the levels we can’t measure?

    Those chaos guys should come back and go over it again.
    Stuff like chaos has become a popular dumping ground for pop culture.

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