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Added beginning of "interpretations" section
A particle is traditionally considered to be fixed at one definite point. However, each particle's position function is a wave, that stretches over space, giving the probability of finding the particle at each point. While there might be a 99% chance of finding a particle within 2 angstroms of a specific location, the function always has nonzero "tails" everywhere else in the universe. This means that there is always an infinitesimal chance of the particle suddenly "jumping" a foot or even a light-year away from its original location.
A particle is traditionally considered to be fixed at one definite point. However, each particle's position function is a wave, that stretches over space, giving the probability of finding the particle at each point. While there might be a 99% chance of finding a particle within 2 angstroms of a specific location, the function always has nonzero "tails" everywhere else in the universe. This means that there is always an infinitesimal chance of the particle suddenly "jumping" a foot or even a light-year away from its original location.
Scientists have tried but failed to find a way to predict where the wave function will "collapse"; that is, where the particle will actually appear. The current prevailing interpretation, the "Copenhagen Interpretation," says that the wave function does ''not'' collapse until someone observes the particle at a certain location. However, [[Schrodinger]], with [[Schrodinger's cat|his famous cat experiment]], raised the obvious question: who, or what, constitutes an observer? What distinguishes an observer from the system being observed? In essence, the Copenhagen Interpretation requires a [[soul]] or something else to distinguish observers from inanimate matter.
Scientists have tried but failed to find a way to predict where the wave function will "collapse"; that is, where the particle will actually appear.
===The uncertainty principle===
===The uncertainty principle===
This is what causes [[Brownean motion]] of dust particles in the air. Due to the uncertainty principle, each individual air molecule moves randomly. At any given time, more molecules are randomly hitting each dust particle on one side than the other; therefore, it randomly floats in one direction.
This is what causes [[Brownean motion]] of dust particles in the air. Due to the uncertainty principle, each individual air molecule moves randomly. At any given time, more molecules are randomly hitting each dust particle on one side than the other; therefore, it randomly floats in one direction.
==Interpretations==
Several interpretations have been advanced to explain how wavefunctions "collapse" to yield the observable world we see.
* The "hidden variable" interpretation<ref>http://www.reasons.org/resources/non-staff-papers/the-metaphysics-of-quantum-mechanics</ref> says that there is actually a [[determinism|deterministic]] way to predict where the wavefunction will collapse; we simply have not discovered it. [[Von Neumann]] attempted to prove that there is no such way; however, [[John Stuart Bell]] pointed out an error in his proof.
* The many-worlds interpretation says that each particle does show up at every possible location on its wavefunction; it simply does so in alternate universes. Thus, myriads of alternate universes are invisibly branching off of our universe every moment.
* The currently prevailing interpretation, the Copenhagen interpretation, states that the wavefunctions do ''not'' collapse until someone observes the particle at a certain location; until someone observes it, it exists in a quantum indeterminate state of simultaneously being everywhere in the universe. However, [[Schrodinger]], with [[Schrodinger's cat|his famous cat experiment]], raised the obvious question: who, or what, constitutes an observer? What distinguishes an observer from the system being observed? In essence, the Copenhagen Interpretation requires a [[soul]] or something else to distinguish observers from inanimate matter.
==Applications==
==Applications==