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The marriage of space and time that heralded the modern era began with the marriage, in 1864, of electricity and magnetism. This remarkable intellectual achievement, based on the cumulative efforts of great physicists such as AndrŽ-Marie Amp�re, Charles-Augustin de Coulomb, and Michael Faraday, was capped by the…
The earth's atmosphere is an imperfect window on the universe. Electromagnetic waves in the optical part of the spectrum (that is, waves longer than X rays and shorter than radio waves) penetrate to the surface of the earth only in a few narrow spectral bands. The widest of the transmitted bands corresponds roughly to…
Try to imagine what the electric and magnetic fields look like at present in the space of this lecture room. First of all, there is a steady magnetic field; it comes from the currents in the interior of the earth - that is, the earth's steady magnetic field. Then there are some irregular, nearly static electric fields…