Schrödinger wrote:
One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour, one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges, and through a relay releases a hammer that 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 psi-function 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.
One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour, one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges, and through a relay releases a hammer that 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 psi-function 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.
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This was a thought-experiment by Schrodinger he developed in order to demonstrate problems with quantum physics.
The basic idea was that you stick a cat in a box, and you have some device based on quantum physics that triggers a cat-killing machine, say a radioactive source that may or may not release a particle. The problem with quantum physics is that it describes the probability of an event, and we imagine these probabilities co-exist. So if we apply quantum mechanics to the cat, we would argue that there is a probability that the cat is alive and dead simultaneously.
The point Schrondinger was making was that cats can't really be alive and dead simultaneously. It's stupid! One of the ideas that developed was that it's only when an observer 'looks' at the cat does the universe decide which probability (alive or dead cat) to present. The problem with this is that a cat is probably intelligent enough to observe it's own alive/dead state! The other issue that arises is, if you need an observer to settle the universe into showing us a live or dead cat, then who is observing the observer to do the same thing to them?
The basic idea was that you stick a cat in a box, and you have some device based on quantum physics that triggers a cat-killing machine, say a radioactive source that may or may not release a particle. The problem with quantum physics is that it describes the probability of an event, and we imagine these probabilities co-exist. So if we apply quantum mechanics to the cat, we would argue that there is a probability that the cat is alive and dead simultaneously.
The point Schrondinger was making was that cats can't really be alive and dead simultaneously. It's stupid! One of the ideas that developed was that it's only when an observer 'looks' at the cat does the universe decide which probability (alive or dead cat) to present. The problem with this is that a cat is probably intelligent enough to observe it's own alive/dead state! The other issue that arises is, if you need an observer to settle the universe into showing us a live or dead cat, then who is observing the observer to do the same thing to them?
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