68111045-1-4-Uncertainty - Uncertainty Principle A...

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Uncertainty Principle A conversation between Einstein and Heisenberg. Heisenberg: "One cannot observe the electron orbits inside the atom. [. ..] but since it is reasonable to consider only those quantities in a theory that can be measured, it seemed natural to me to introduce them only as entities, as representatives of electron orbits, so to speak." Einstein: "But you don't seriously believe that only observable quantities should be considered in a physical theory?" "I thought this was the very idea that your Relativity Theory is based on?" Heisenberg asked in surprise. "Perhaps I used this kind of reasoning," replied Einstein, "but it is nonsense nevertheless. [. ..] In reality the opposite is true: only the theory decides what can be observed." The microscopic world has a property called "wave particle duality." (So does the macroscopic world, but the effects of wave particle duality aren't noticeable for large objects.) What this means is that every particle, such as a photon, electron, proton, positron, and so on, has a wave associated with it. The amplitude (size) of this wave describes the probability of finding the particle in that region. In any observation of the particle, it will probably be found where the amplitude is large, and will probably not be found where the amplitude is small, but there's an uncertainty in the position of the particle. The wave will generally not be spread throughout the entire universe, but will be confined to a small region in space. This "localized" wave is called a wave packet. A wave packet does not
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68111045-1-4-Uncertainty - Uncertainty Principle A...

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