[visualops]

"Quantum theory, as first introduced by Plank in 1900, is based on the concept of using the quantum unit to describe the dynamic properties of subatomic particles and interactions of matter and radiation. It is a departure from the classical Newtonian mechanics in which certain physical quantities (velocity, acceleration, position) can only have individual discrete values assigned to them. Quantum mechanics gives a statistical description of the behaviour of physical systems.

Heisenberg's Uncertainty Principle discusses the calculation of the uncertainty in the measurements of momentum and position of a particle. A consequence of the principle is that any measurement of a system must disturb the system under investigation, with a resulting lack of precision in the measurement. Erwin Schrodinger proposed an illustration of the problem of viewing these particles in a "thought experiment":

"Suppose we put a cat in a cage with a radioactive atom, a Geiger counter, a hammer, and a poison bottle; further suppose that the atom in the cage has a half-life of one hour, a fifty-fifty chance of decaying within the hour. If the atom decays, the Geiger counter will tick; the triggering of the counter will activate the hammer, which will break the poison bottle, which will kill the cat. If the atom doesn't decay, none of the above things happen, and the cat will be alive. Now the question, What is the state of the cat after the hour?"

Schrodinger's thought experiment asks whether the cat is dead or alive after an hour. The most logical solution would be to wait an hour, open the box, and see if the cat is still alive. However once you open the box to determine the state of the cat you have viewed and hence disturbed the system and introduced a level of uncertainty into the results. The answer, in quantum mechanical terms is that, before you open the box the cat is in a state of being half-dead and half-alive.

This paradox arises because the atom, being microscopic, must be described by quantum mechanics. Therefore after one hour inside the box, before it has been observed, the atom is in a state of superposition of being both undecayed and decayed. Therefore, as the state of the cat in the box is directly related to the state of the atom, the cat must also be in a state of superposition being both dead and alive. This is known as a coherent superposition, many different solutions exist simultaneously. However the superposition breaks down as soon as the cat is observed as dead or alive."

[-YYZ-]

The real question in quantum mechanics, and I believe it remains so, is whether quantum superpostions of objects at the macro level really do exist. We know that quantum effects at the particle scale are real enough, as can be seen in the classic two-slit experiment, but do they scale up to the macro level that we live in, or do they collapse at some particular scale?

[keats5]

Well, I didn't understand all that. But I think they should have used a rat instead.