Stored here for reference. I posted this on the book of faces 5 years ago having got it from (I think) a mailing list, though I could be wrong about the origin.

Q: How can one small 9 pound cat take up a third or more of a queen sized bed?!

A: Actually it’s all due to Quantum. You can blame Schroedinger and Heisenberg for involving cats in the whole quantum thing, but once they were in cats have stuck with it because they like it.

Essentially (and this also explains the lying on chairs you are about to sit on, newspapers/books you want to read etc. ) cats are potentially distributed everywhere in a wave function until you don’t make an observation. Then their waveform collapses to produce a feline particle exactly where you don’t want it to be.