Jason Cohen
Jul 22, 2017 · 3 min read

I think you’re taking too literally some of the layman-simplifications of quantum mechanics.

When we say things like “observation changes the system,” that’s not exactly right. It’s a useful simplification, in the same way that we say “images appear in mirrors because light takes the shortest path.” That is not the reason, and indeed it’s easy to observe with a laser pointer and a mirror that light takes all of the paths. But it turns out that in the shortest path there is constructive interference and for most of the mirror there is destructive-to-zero. So saying “light takes the shortest path” is strictly false, but a perfectly fine simplification to help us “chunk” things so they’re easier to reason about.

Going back to quantum mechanics, it’s not the act of observing that affects the system, it’s anything that could in principle allow someone to observe. The act of observing is not required. For example, in the double-slit experiment, there are a variety of tricks for detecting which slit the particle went through, e.g. hitting it with another particle or allowing the slit apparatus itself to move and measuring the change in momentum to understand the path. All of these things cause the interference pattern to vanish. But the key point is, no one has to actually observe those things for the pattern to vanish. Just making it theoretically possible to know which slit, causes it to vanish. So this shows that it’s not an “intelligence observing” that’s causing the behavior to change. In a universe before life, the universe would still act this way.

The other aspect I think you’re misinterpreting is the uncertainty principle. You write as if this is (potentially) a computational artifact or a way in which a computational system could separate internal from external state or avoid having to compute / store information or so on.

But this is not how uncertainty arises. Uncertainty is a purely mathematical consequence of any wave, whether connected with physics or not. A good way to think of it is the pairing of a wave with its Fourier transformation. In fact, this is exactly correct for quantum mechanics, and all of the Heisenberg pairs (like the famous pairing of dx and dp, i.e. the more you know about position the less you know about momentum) are exactly this pairing, and it’s why there are many such pairs besides the famous one.

Consider an extreme case of sin(x) as the wave. The Fourier transform (maybe think of it as the Power Spectrum for further simplification) is simple and discreet — a single spike line at the frequency of the sine wave. In this case, sin(x) is representing location and the FP (let me abbreviate Fourier Power) is representing momentum. In this case momentum is known exactly — that’s the meaning of the “one spike.” But position is completely unknown — sin(x) is not localized, it extends infinitely in all directions.

How could we localize a wave? Imagine adding more waves of different wavelengths that constructively interfere in one spot (call it the origin for simplicity), but destructively interfere far away. This is actually quite easy to do. Then you end up with a sort of “fuzz ball” near the origin and “zero” far away. We have achieved pretty good bounds on the location of the energy! But you look at the FP and now there’s lines all over the place because we had to add all these different waves together with various frequencies and amplitudes. So we don’t have a sense of momentum.

All of the above has nothing to do with physics. It’s just a mathematical result of waves.

So when we say “the universe doesn’t let us know dx and dp with greater accuracy than dx*dp=h,” what we’re really doing is anthropomorphizing the mathematical fact that dx and dp are related in the above manner, and thus it’s a consequence of the experimental fact that particles are wave-packets, i.e. they are wave-like but also localized as a particle as we just built up in our example.

This does not imply anything an intelligent observer or computation. It’s just what waves do, and then we try to say useful simplifications about it to help us wrap our heads around it.

I’m not trying to argue that the universe is not a computation or simulation. None of the above proves it is or isn’t.

But, the fact of quantum uncertainty doesn’t, in my mind, bolster the argument for computation or simulation. It’s just a consequence of “everything is a wave.”

    Jason Cohen

    Written by

    Keyword, buzzword, half-truth, adjective, hey look at me!