ScienceDaily (Nov. 12, 2007) – The big world of classical physics
mostly seems sensible: waves are waves and particles are particles, and
the moon rises whether anyone watches or not. The tiny quantum world is
different: particles are waves (and vice versa), and quantum systems
remain in a state of multiple possibilities until they are measured –
which amounts to an intrusion by an observer from the big world – and
forced to choose: the exact position or momentum of an electron, say.
On what scale do the quantum world and the classical world begin to
cross into each other? How big does an “observer” have to be? It’s a
long-argued question of fundamental scientific interest and practical
importance as well, with significant implications for attempts to build
solid-state quantum computers.