London Lecture 2010
ANTHONY J.
LEGGETT
University of Illinois
Nobel Prize 2003
Does the everyday world really
obey quantum mechanics?
Quantum mechanics has been enormously successful in describing nature at
the atomic level, and most physicists believe that it is in principle the
"whole truth" about the world even at the every-day level. However,
such a view prima facie leads to a severe problem: in certain circumstances,
the most natural inter-pretation of the theory
implies that no definite outcome of an experiment occurs until the act of
"observation". For many decades this problem was regarded as
"merely philosophical", in the sense that it was thought that it had
no consequences, which could be tested in experiment. However, the situation
has changed dramatically in this respect in the last dozen or so years. I will
discuss the problem, some popular "resolutions" of it, the current experimental
situation, and prospects for the future.