Lightbulbs and Quantum Physics (04 Sep 2002)

Discovered a MAP_GROWSDOWN flag in asm/mman.h, unfortunately it doesn't seem to do what one would hope.

Stand have a longish entry on the UK-DMCA. They suggest that the chances of parliament nullifing it are pretty much nil (which, I guess, is depressingly true), and suggest that people write to the UK Patent Office and the Secretary of State for Trade and Industry and try to get more opt-out clauses into the UK law. There has been far too little press coverage about this so far. I've contacted New Scientist, so hopefully they will have something.

There's also a chance that NS will have a short section on the IOI. I only hope they don't include that god awful photo of the team taken at Cambridge. (and, no, I'm not giving the link!)

One of the defining characteristics of quantum physics, over and above the classical, it that it is non-deterministic. Many people have had problems with this, most famously Einstein ("God does not play dice!"). A deterministic universe is very comforting to some people (myself half included) and certainly sits nicely with the logical worlds of maths and computers.

Since many classical processes are statistically modelled (for example, temperature) because it's not useful deal at the level of individual, vibrating molecules some have suggested that the only reason that quantum physics looks non-deterministic is because we are only seeing the cumulative effects of an underlying deterministic system. These ideas are usually called hidden variable theories.

I'm going to run over an argument that TBL gave to me and that's pretty much convinced me to give up on hidden variable theories.

Imagine a light bulb which, at time t, is either on or off and its state is totally random. That's non-deterministic. Not imagine that a pseudo-random number generator (or a Rule 30 CA if you wish, Mr Wolfram) is hidden in the light bulb and actually governs the bulb's state. Given enough time we might be able to reverse the PRNG and that would be a deterministic universe.

Now, our quantum universe might be really non-deterministic or it might have a deterministic process underlying it. However, Bell's Theorem shows that, if there is an underlying deterministic process, then it cannot be localised. So you could not take a section of the universe and have it be deterministic, only (possibly) the whole universe. However, we are in the universe, and so cannot measure every roll of the dice. So in the end you might as well give up on it being deterministic, because it would be a useless determinism anyway.