Friday, November 30, 2007

Schroedinger's universe

Quantum physics is not for the weak hearted. Sure the mathematics is simple - I mean what is as simple as |psi> = 1/sqrt(2)(|0> + |1>)? Well it turns out that this equation is the heart of the troubles. You see this equation says that a quantum state can exist as a superposition of one or more states until it is observed after which it is reduced to either one or the other (|0> or |1> in the equation above). This, in a nutshell, is Schroedinger's favourite cat.

A paper by Lawrence M. Krauss, which can be found here, implies that an act of observation on the age of the universe from inside the universe reduces the universe into one of many possible destinies. Here's my take on it: Bollocks. The universe is a closed system - an act of observation or even the ability to make an observation from inside the universe should have no effect whatsoever on the destiny of the universe. It's a bit like the electron being the observer of it's path through a double slit and thus preventing it from interfering with itself. Obviously it doesn't happen.

I should clarify that Lawrence M. Krauss did stipulate that there is no causal relationship ie. our observation of the supernova that resulted in the conclusion that the universe's expansion is accelerating has no effect whatsoever on the age or destiny of the universe but that the mere possibility of our being able to make that measurement does imply something about which of the many quantum destinies the universe will follow. While we didn't cause the universe to become unstable, Krauss suggests that just by being able to make an internal observation can have some implication on the outcome. Going back to the electron, can the electron somehow be able to measure which of the slits it will travel through? I suspect that the answer is no.

If there is something observing the universe from outside, that's a different story entirely but I'm not sure that there is an "outside" to the universe. Lesson learned - quantum physics is a weird thing and it is hard to get our puny brains around it. Physicists have been struggling for almost a century to interpret the weirdness of quantum physics. I guess we will be struggling for some time longer.

Peter Woit discusses the paper in more detail here.

No comments: