Schrödinger's cat

thumb In quantum mechanics, Schrödinger's cat is a thought experiment concerning quantum superposition. In the thought experiment, a hypothetical cat inside a closed box may be considered to be simultaneously both alive and dead while it is unobserved, as a result of its fate being linked to a random subatomic event that may or may not occur. This experiment, viewed this way, is described as a paradox. This thought experiment was devised by physicist Erwin Schrödinger in 1935, in a discussion with Albert Einstein, to illustrate what Schrödinger saw as the problems of Niels Bohr and Werner Heisenberg's philosophical views on quantum mechanics. Quotes One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following diabolical device (which must be secured against direct interference from the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small that perhaps in the course of one hour one of the [radioactive] atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The first atomic decay would have poisoned it. The [quantum wavefunction] of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts. Erwin Schrödinger in The Present Situation in Quantum Mechanics (1935): We cannot predict the behaviour of the photon, and thus, once it has behaved, we cannot predict the state of the system it has determined. We cannot predict it! God plays dice with the world! So it is beautifully demonstrated that if you desire certainty, any certainty, you must create it yourself Ursula K. Le Guin in Schrödinger’s Cat (1974) In fact, the mere act of opening the box will determine the state of the cat, although in this case there were three determinate states the cat could be in: these being Alive, Dead, and Bloody Furious. Terry Pratchett in Lords and Ladies (1992) External links Category:Quantum mechanics