 Quantum Mechanics
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 Podcast
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Looking back at previous physics episodes -- all modern physics really deals with "edge" scenarios, out of the realm of everyday experience.
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Special relativity -- very fast
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General relativity -- very large, very heavy
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Quantum mechanics -- very small, very low energy, very high energy
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 Core to understanding quantum mechanics -- the nature of light, and of atoms.
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But let's start a bit earlier for the real history
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In 1690, Christian Huygens explained the laws of reflection and refraction on the basis of a wave theory.
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In the 18th century, Sir Isaac Newton pushed back against the wave theory of light, and proposed that light consisted of particles which he called corpuscles. He was so successful at popularizing this view that his theory was essentially unquestioned for nearly 100 years.
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In 1827 Thomas Young and Augustin Fresnel performed experiments on interference; the results could not be explained under the corpuscular theory.
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In 1873 James Clerk Maxwell showed that by making an electrical circuit oscillate it should be possible to produce electromagnetic waves.
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The real beginnings of quantum mechanics date from the work of Max Planck in 1900.
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The photoelectric effect
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Einstein built on Planck's idea -- in 1905, proposed that electromagnetic radiation itself was quantized (we call them photons).
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In 1913, Niels Bohr realized that the orbit of an electron about an atomic nucleus could be stabilized by applying the idea of energy quanta to the orbits of electrons.
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The Bohr atom model was enlarged upon with the discovery by de Broglie in 1924 that the electron has wave-like properties. Actually, under the de Broglie hypothesis, all matter has wave-like properties, but the electron's place in this was experimentally confirmed first.
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In the 1920's, Werner Heisenberg & Erwin Schrödinger were "racing" each other to develop better mathematical foundations for QM.
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Heisenberg's probabilistic approach became known as the Copenhagen interpretation of quantum mechanics.
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The term "quantum mechanics" was first coined by the physicist Max Born in 1924.
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Later, the field was further expanded with work by Julian Schwinger, Murray Gell-Mann, and Richard Feynman, in particular, with the development of Quantum Electrodynamics in 1947.
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Quantum mechanics is a more fundamental theory than Newtonian mechanics and classical electromagnetism, in the sense that it provides accurate and precise descriptions for many phenomena that these "classical" theories simply cannot explain on the atomic and subatomic level.
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Broadly speaking, quantum mechanics successfully explains four classes of phenomena that classical physics cannot account for:
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The quantization (discretization) of certain physical quantities -- photoelectric effect, etc.
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Wave-particle duality -- of both light and subatomic matter
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The uncertainty principle
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Quantum entanglement
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Note: quantum mechanics can be formulated in either a relativistic or non-relativistic manner
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Wrapup
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Most physicists believe that quantum mechanics provides a correct description for the physical world under almost all circumstances. Despite the success of quantum mechanics, it does have some controversial elements.
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Probabilistic element seems to cause people the most problems
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Unfortunately, since QM is well exposed (everybody's heard of it, even if few really understand it) and so incredibly weird, it's been grossly misused in popular culture lately
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Despite its issues, there is no other theory to replace quantum mechanics that is so successful at the quantum level.
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The question of how to overcome the contradiction between quantum mechanics & general relativity remains an area of active research.
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Sources and other links
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What the Bleep...
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