Wednesday, October 6, 2010

The randomness at the heart of reality

Is reality ultimately based on randomness? How one answers this question ultimately colors one's outlook (I suggest) in deep and subtle ways. Of course, there are many ways one could approach the issue and there are ambiguities in the question itself. But I am drawn to such questions as this (as a moth to a flame?) and, since I read and think about them, I might as well write about them here from time to time.

Here, then, are a few notes about Vlatko Vedral's view of the issue ...

Vedral draws a distinction between "classical superficial randomness" (e.g. coin tosses) and "quantum fundamental randomness" (see Decoding reality (OUP, 2010), p.163). Randomness approximates to unpredictability and much in our world appears random because it is impossible to predict in practice even if in theory one could do so using the methods of classical physics (if one had all the relevant data etc.). But the quantum world is different. No prediction can be made (even in theory) of certain quantum events. Quantum theory embraces randomness, and sees some quantum phenomena as random in a fundamental sense.*

We can think of scientific theories, Vedral writes (p. 166), as computer programs "with the output being the result of whatever experiment we are trying to model. We say that our theory is powerful, if we can compress all sorts of observations into very few equations."

But any theory will be finite and will (as Gregory Chaitin first fully realized within information theory) only produce a finite set of results. "In other words, there will be many experimental outcomes that could not be compressed within the theory. And this effectively implies that they are random." (p. 167)

Is the randomness in quantum theory due to the theory's incompleteness - our lack of knowledge of a more detailed deterministic underlying theory - as some people think? Or is "randomness inherent in the Universe, and therefore ... [an essential] part of any physical description of reality? Randomness could simply be there because our description of reality is always .... finite and anything requiring more information than that would appear to be random (since our description could not predict it)." (p. 167-168)

Vedral states what he sees as a "very profound conclusion" that this view implies: "that randomness in quantum physics is far from unexpected - in fact according to this logic it is actually essential. Furthermore, it would mean that whatever theory - if any - superseded quantum physics, it would still have to contain some random features." (p. 168)

To me it matters (or seems to matter) whether or not randomness is at the heart of things. Does it matter to you?

* I have revised this passage slightly in response to a comment.