Listen to Rossini's Cats Duet
How are Syracuse & Archimedes related?
What has the Wall Street in NY got to do with Holland?
Revolutionary Disagreement Resolution Method
Schrödinger's cat is a famous illustration of the principle in
quantum theory of superposition, proposed by Erwin Schrödinger
in 1935. Schrödinger's cat serves to demonstrate the apparent
conflict between what quantum theory tells us is true about the
nature and behavior of matter on the microscopic level and what
we observe to be true about the nature and behavior of matter on
the macroscopic level.
(theoretical) experiment: We place a living cat into a steel
chamber, along with a device containing a vial of hydrocyanic
acid. There is, in the chamber, a very small amount of a
radioactive substance. If even a single atom of the substance
decays during the test period, a relay mechanism will trip a
hammer, which will, in turn, break the vial and kill the cat.
The observer cannot know whether or not an atom of the substance
has decayed, and consequently, cannot know whether the vial has
been broken, the hydrocyanic acid released, and the cat killed.
Since we cannot know, the cat is both dead and alive according
to quantum law, in a superposition of states. It is only when we
break open the box and learn the condition of the cat that the
superposition is lost, and the cat becomes one or the other
(dead or alive). This situation is sometimes called quantum
indeterminacy or the observer's paradox: the
observation or measurement itself affects an outcome, so that it
can never be known what the outcome would have been if it were
We know that
superposition actually occurs at the subatomic level, because
there are observable effects of interference, in which a single
particle is demonstrated to be in multiple locations
simultaneously. What that fact implies about the nature of
reality on the observable level (cats, for example, as opposed
to electrons) is one of the stickiest areas of quantum physics.
Schrödinger himself is rumored to have said, later in life, that
he wished he had never met that cat.