A paradox in quantum mechanics that considers the unhappy fate of a cat enclosed in a box together with a cyanide capsule. Since the cat cannot be observed while it is sealed inside, the wavefunction of the cat must be described as a superposition of wavefunctions, one of which corresponds to an intact capsule and a live cat, and the other of which corresponds to a broken capsule and a dead cat. Opening the box to look inside thus causes the wavefunction to collapse into one of these two distinct states. This results in the paradox that the act of simply observing the fate of the cat causes it to become either definitely alive or definitely dead.
References
Basdevant, J.-L. and Dalibard, J. "Schrödinger's Cat." Ch. 5 in The Quantum Mechanics Solver: How to Apply Quantum Theory to Modern Physics. Berlin: Springer-Verlag, pp. 27-37, 2000.
Erickson, G. W. and Fossa, J. A. Dictionary of Paradox. Lanham, MD: University Press of America, pp. 180-181, 1998.
