Redefining Reality - The Intellectual Implications of Modern Science

With quantum mechanics, according to Schrödinger’s
formulation, the state variable is represented by the Greek letter
psi (), the wave function. But what is the wave function?
What does it represent?
It can be expressed in terms of any given observable, but then,
according to the theory, it is a combination of every possible
state the system could be in; the term used by physicists is
a . If we express in terms of position,
then according to Schrödinger’s equation, the object will
simultaneously be in every place it could be. Of course, things
are not spread out through space; everything we see is in a place.
And here is the real strangeness in quantum mechanics: When
we do not observe a system, it obeys Schrödinger’s equation
and is in its superposed state. The moment we observe it, it
collapses into one of its states, where we can see it, but we
cannot tell which value it will take.
This superposition plays into the question of whether light is a
particle or a wave. The answer depends on how you observe.
If we turn down a light
source until we have just
one packet of light—a
photon—coming out at a
time, we can shoot it at a
wall with two slits cut in
it. If light is a wave, then
it should go through both
slits at the same time. As
a result of the adding and
subtracting behavior of
waves, the light would
show up on a screen
behind the slits as a
series of alternating light
and dark bands. If light
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