emperor_of_localgroup":2ydrn522 said:
darkmatter4brains":2ydrn522 said:
Even the description of the electron as a point particle more or less breaks down on distance scales smaller than the compton length.
Lots of weird stuff in Quantum Theory ....
I understand electrons do weird things on quantum level.
What surprises and amazes me is the consistency of electric current. If the basic definition of electric current is correct, we may then come to a conclusion, like photons, free electrons act like particles and electrons bound to atoms act like waves or are better described by wave functions. IMO, huge number of free electrons and their motions in a conducting wire can not be precisely represented by wavefunctions.
Well, many things that are quantized do look continous at a macroscopic level. Thanks to the very, very small magnitude of the fundamental constant of quantum mechanics (hbar), most discrete levels are extremely tiny. So, many things that are quantized and discrete, look virtually continuous at the macroscopic level.
Also, a current is (
very roughly) like water in a garden hose. Picture a hose that is
full of water. When you turn on the spicket, you almost instantly have water popping out one end. That's not because the water molecules at the spicket end instantly traveled all the way through the hose, because they didn't. But, you can
very roughly picture one water molecule bumping into the next, which in turn bumps into the next, all the way down the line, until the one near the end gets pushed out. Same with current. Most of the individual electrons are taking some erratic path through the wire, and hardly getting anywhere. Check out the drift speed section (a somewhat bad description, but it gets the point across) on this Wiki page:
http://en.wikipedia.org/wiki/Electric_current
Also, within quantum mechanics the wave function description is always valid. But the description of wave-like nature in Quantum Mechanics is different than what we're used to from Classical Mechanics. In quantum mechanics we're dealing with a probability wave, which isn't really a physical wave, like standing waves on a string are, or a sound wave. (Although, there is still some debate on this) The square of the amplitude of the wave function gives the probabilities of where you are likely to find the particle (or the value of some other observable, like spin) upon measurement.
Let's not forget about wave/particle duality, either. All quantum phenomenon can act like either a particle or a wave, and most often as both, depending on what's going on. You can also picture a wave function shaped like a delta dunction, which moves around upon time evolution, and that's basically a description of a what we normally picture for a classical particle, at least from the perspective of position.
Quantum Mechanics of course is only valid in it's domain. It also doesn't allow the creation/annihiliation of particles. Quantum Field Theory takes over when relativistic effects are important, but is once again only valid to certain energy levels. At high energies we need a new theory, and String Theory looks like the most likely candidate. But, one thing these all share, is a quantum description of the world, which does not have the deterministic descriptions we're used to in Classical Mechanics. Determinism is gone for good, I think.