“Decoherence is what destroys the possibility of observing macroscopic superpositions – including Schrödinger’s live/dead cat. And this has nothing to do with observation in the normal sense: we don’t need a conscious mind to ‘look’ in order to ‘collapse the wavefunction’. All we need is for the environment to disperse the quantum coherence. This happens with extraordinary efficiency – it’s probably the most efficient process known to science. And it is very clear why size matters here: there is simply more interaction with the environment, and therefore faster decoherence, for larger objects.”