Erwin Schrödinger, one of the fathers of quantum mechanics, is famed for a number of important contributions to physics, especially the Schrödinger equation, for which he received the Nobel Prize in Physics in 1933. Schrödinger proposed in 1935 in the following theoretical experiment. A cat is placed in a steel box along with a Geiger counter, a vial of poison, a hammer, and a radioactive substance. When the radioactive substance decays, the Geiger detects it and triggers the hammer to release the poison, which subsequently kills the cat. The radioactive decay is a random process, and there is no way to predict when it will happen. Physicists say the atom exists in a state known as a superposition both decayed and not decayed at the same time. Until the box is opened, an observer doesnt know whether the cat is alive or dead because the cats fate is intrinsically tied to whether or not the atom has decayed and the cat would, as Schrödinger put it, be living and dead ... in equal parts until it is observed. (More physics: The Physics of Waterslides.) In other words, until the box was opened, the cats state is completely unknown and therefore, the cat is considered to be both alive and dead at the same time until it is observed. If you put the cat in the box, and if theres no way of saying what the cat is doing, you have to treat it as if its doing all of the possible things being living and dead at the same time, explains Eric Martell, an associate professor of physics and astronomy at Millikin University. If you try to make predictions and you assume you know the status of the cat, youre [probably] going to be wrong. If, on the other hand, you assume its in a combination of all of the possible states that it can be, youll be correct. Immediately upon looking at the cat, an observer would immediately know if the cat was alive or dead and the superposition of the cat the idea that it was in both states would collapse into either the knowledge that the cat is alive or the cat is dead, but not both. Schrödinger developed the paradox, says Martell, to illustrate a point in quantum mechanics about the nature of wave particles. What we discovered in the late 1800s and early 1900s is that really, really tiny things didnt obey Newtons Laws, he says. So the rules that we used to govern the motion of a ball or person or car couldnt be used to explain how an electron or atom works. At the very heart of quantum theory which is used to describe how subatomic particles like electrons and protons behave is the idea of a wave function. A wave function describes all of the possible states that such particles can have, including properties like energy, momentum, and position. The wave function is a combination of all of the possible wave functions that exist, says Martell. A wave function for a particle says theres some probability that it can be in any allowed position. But you cant necessarily say you know that its in a particular position without observing it. If you put an electron around the nucleus, it can have any of the allowed states or positions, unless we look at it and know where it is. Thats what Schrödinger was illustrating with the cat paradox, he says. In any physical system, without observation, you cannot say what something is doing, says Martell. You have to say it can be any of these things it can be doing even if the probability is small.
Posted on: Thu, 04 Dec 2014 06:48:56 +0000
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