Monday, March 9, 2009

The Preposterous Universe

Two teams of physicists have observed Hardy's paradox, proving again the exceptional bizarreness of the quantum world. Physicist Lucien Hardy proposed in the 1990's that quantum uncertainty meant that an understanding of unobserved past events was compromised by the acknowledgement that the act of observation changes events. This supposed that, when unobserved, particle and antiparticle pairs could survive their meeting instead of jointly annihilating as conventionally understood. Or, generally, that real and very strange things could be happening that we couldn't know about.

Now, using novel methods, researchers have managed to observe photon interactions without biasing the interaction. The results were strange indeed, The Economist:

What the several researchers found was that there were more photons in some places than there should have been and fewer in others. The stunning result, though, was that in some places the number of photons was actually less than zero. Fewer than zero particles being present usually means that you have antiparticles instead. But there is no such thing as an antiphoton (photons are their own antiparticles, and are pure energy in any case), so that cannot apply here.

The only mathematically consistent explanation known for this result is therefore Hardy’s. The weird things he predicted are real and they can, indeed, only be seen by people who are not looking. Dr Yokota and his colleagues went so far as to call their results “preposterous”. Niels Bohr, no doubt, would have been delighted.