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Predictability and Measurement

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The fact of conscious volitional entities implies that the future cannot be predicted with certainty.

If one measures a precisely observable state variable of an isolated system regularly, one will obtain the same answer each time, independent of the frequency of measurement, because the state cannot change unless the system interacts with another system.

In reality, it is not possible to isolate a system from the rest of existence. Over time, depending both on the level of interaction with impinging systems (such as photons) and the frequency of measurement, the state of a regularly observed system may change between measurements. And the Law of Entropy indicates that, statistically speaking, the system state is more likely to become less ordered than more due to haphazard "background" interactions.

In everyday terms, i.e., macroscopically, this shows up as visible decay of longstanding structures. For example, your abode is more or less in the same state as you left it in the morning, when you return in the evening of a busy day. But over a span of years, the state of your abode will visibly and functionally decay (dang it!).

Microscopically, decay of excited states is the rule.

The only difference between the micro and macro cases is the scale of the system involved, and hence the lifespan of the observed state.

For a house, the lifespan of its state is probably immeasurably tiny, so tiny that it appears impossible to construct a device to measure the state of the house twice in quick enough succession to obtain the same precise result. This is because the house is a high-frequency agglomeration of bajillions of atoms, each acting as a potential state change lever.

For an electron, the lifespan of a polarized spin state (half-spin state) in a dark vacuum is of macroscopic duration, and one can make regular measurements at relatively low frequencies without observing variance in the result. Eventually, however, the electron will decay into its unpolarized (zero-spin) state (which latter is more entropically favorable, hence the state in which one usually finds electrons "in the wild").

The electron spin state is more stable than that of the house; the electron interacts less with its ambient environment, so its state is less likely to decay over any given period of time.

However, it is not the precise micro state of the house that is important to the person who lives in it; rather it is the macroscopic average state that matters. In this sense, the house does indeed last longer than the electron remains in an excited spin state -- within the parameters of one's ability to discern with the senses, the result of measuring a property of the house's macro-state is more predictable than the result of measuring an electron's micro-state.

Once a measurement is taken its result is a fact. By observing and understanding patterns among facts generated by measuring similar systems, one becomes more able to predict the outcomes of future measurements of such systems. Because the state of a system may change between measurements, however, perfect predictability is not an option.

All that one can do as a limited being is learn to predict outcomes just precisely enough to enable one to engineer a future, i.e., to enable one to plan long range.


- David

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