There is no reason (that we yet know of) why in principle objects cannot remain in coherent quantum states no matter how big they are – provided that no measurement is made on them. But it seems that measurement somehow does destroy quantum coherence, forcing us to speak of the wavefunction as having ‘collapsed’. If we can understand how measurement unravels coherence then we would be able to bring measurement itself within the scope of quantum theory, rather than making it a boundary where the theory stops. We might even be able to figure out what happens to Schrödinger’s cat. (But I make no
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