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318 Are the Androids Dreaming Yet?

Uncertainty
If you know a little of quantum mechanics you might imagine Heisenberg’s Uncertainty Principle comes to our rescue.

Heisenberg’s principle is often misunderstood. People sometimes try to explain it as an experimental problem. If I want to measure the position of a particle I am going to need to shine a light on it. The photons I use to illuminate the particle will knock it out of position so the act of measurement disturbs the system. This is not the Uncertainty Principle. It is a different but related effect, called the measurement problem. The muddle is really Heisenberg’s own fault. When he tried to produce a layman’s explanation he used the analogy of disturbing the particle with the photon. This is wrong. A photon would not disturb a particle enough to explain the uncertainty we find; particles are fundamentally uncertain even before we measure them. Heisenberg’s Uncertainty Principle is a quantum property, which means it makes no sense and there is no analogy I can give you to properly explain it! Here is the closest thing I can find.

Imagine I am playing a musical note on a guitar. You might want to know two things about it; where exactly is the string and what pitch, or note, am I playing? The problem with these two measurements is they can’t be stated at the same time. Pitch is dictated by the rate of oscillation over time: the number of times a string vibrates back and forth per second. Position is the exact location of the string at a given moment in time. If I state the position precisely this has no pitch because pitch needs a time interval. If I allow a time interval the string will move during that time and it won’t be precisely in one place. The best I can say is the string is about two millimeters above the fret board and two-thirds of the way across it.

So, I hear you cry, this Uncertainty Principle means our Universe is not deterministic because it is uncertain.

Unfortunately, the principle only prevents us from measuring the position and momentum of a particle at the same time, it does not prevent the Universe knowing the information it needs to allow the particle to go about its business in an entirely deterministic fashion. There is a perfectly reliable and predictable wave function that governs the motion of every particle, just as there is an entirely predictable equation for the motion of a string on a musical instrument.

If both the classical and quantum laws of physics are deterministic where does the freedom come from to make our Universe non-deterministic? There is just one place to look: you and me.

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