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offers hundreds of annotated lessons, simulations, and resources for teaching topics in the physical sciences, including astronomy, classical mechanics, electricity and magnetism, fluid mechanics, general physics, modern physics, optics, oscillations and waves, quantum physics, and thermodynamics and statistical mechanics. (National Science Foundation)
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The existence of black holes was predicted well before the 20th century. About a hundred years after Newton worked out his theory of gravitation, the English astronomer John Michell recognized in 1784 the possibility that the gravity of a very large star might be so great that nothing, not even light, could escape it. |
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Northern lights |
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