Schrödinger's cat is a famous thought experiment illustrating the strange properties of elementary
particles.
Under this experiment, a cat is placed inside a closed box with a canister of poison and a radioactive atom initially
prepared in the metastable state. The radioactive atom has a 1/2 probability of decaying in one hour. If it decays,
the poison is released, and the cat dies.
Imagine placing the cat in the box, closing the lid, and waiting for an hour. Could you tell, at the end of that
hour, whether the cat is dead or still alive?
In the ordinary world, the answer is simple. One just has to open the lid to see if the cat is dead or alive.
The quantum world, however, doesn't allow such observation. Instead, one has to surmise that there is a 50% chance
that the cat is dead, or in other words, that the cat is in an indeterminate state—neither dead nor alive,
or maybe both. The moment one opens the lid, this state of indeterminacy collapses, and the cat is either dead
or alive.
This kind of conundrum—an ambiguous state of being neither this nor that, or maybe both this and that at
the same time—is typical of the quantum world.
