Starkist
06-29-2003, 04:27 AM
Reprinted from some website:
Imagine you had a radioactive atom. Radioactive atoms have surplus energy and are unstable. At any moment it will give out this surplus energy and return to being a normal atom. There is no law in physics which allows us to say EXACTLY when this will happen. All we know is the PROBABILITY of it happening at a given time. We say it is in two 'states' - one excited and one unexcited. According to quantum mechanics as soon as we measure the atom it will definitely be in one state or the other, but until then the atom is in between, it is in a 'superposition' of each state (that is, it's a bit of both). This is fine when dealing with things like atoms, which are small and so obey the rules of quantum mechanics, but what about big things? One day, a guy called Edwin Schrodinger came up with an idea for an experiment. Put a cat into a box (he said) with a fragile bottle of a deadly poison, a hammer and a radioactive atom. If the atom decays then a mechanism detects this and swings the hammer, breaks the bottle of poison and the cat dies. If the atom doesn't decay the mechanism doesn't move the hammer, the poison stays in the bottle and the cat lives. As before, until we open the box to measure the atom we don't know which state the atom is in, it is in a mixture of the two. But, and this is the whole point of the problem, what has happened to the cat? Is the cat, like the atom, in a mixture of states - both dead and alive? So what's happened to the cat?
Quantum mechanics are fun late at night when I'm half asleep... I'll bet Toolie (R.I.P.) would enjoy this one.
Imagine you had a radioactive atom. Radioactive atoms have surplus energy and are unstable. At any moment it will give out this surplus energy and return to being a normal atom. There is no law in physics which allows us to say EXACTLY when this will happen. All we know is the PROBABILITY of it happening at a given time. We say it is in two 'states' - one excited and one unexcited. According to quantum mechanics as soon as we measure the atom it will definitely be in one state or the other, but until then the atom is in between, it is in a 'superposition' of each state (that is, it's a bit of both). This is fine when dealing with things like atoms, which are small and so obey the rules of quantum mechanics, but what about big things? One day, a guy called Edwin Schrodinger came up with an idea for an experiment. Put a cat into a box (he said) with a fragile bottle of a deadly poison, a hammer and a radioactive atom. If the atom decays then a mechanism detects this and swings the hammer, breaks the bottle of poison and the cat dies. If the atom doesn't decay the mechanism doesn't move the hammer, the poison stays in the bottle and the cat lives. As before, until we open the box to measure the atom we don't know which state the atom is in, it is in a mixture of the two. But, and this is the whole point of the problem, what has happened to the cat? Is the cat, like the atom, in a mixture of states - both dead and alive? So what's happened to the cat?
Quantum mechanics are fun late at night when I'm half asleep... I'll bet Toolie (R.I.P.) would enjoy this one.