Conventional wisdom, even to this day, dictates that accelerating charges necessarily give off electromagnetic radiation. This is seen, for instance, in large-scale particle accelerators (synchrotrons), such as the Tevatron at Fermilab and the soon-to-be-operational LHC at CERN: the charged particles moving around the ring are constantly shedding radiation over a range of frequencies, including X-rays.
In the first post in my series on the physics of invisibility, however, we discussed a little-known 1910 paper by Paul Ehrenfest, in which he demonstrates theoretically that one can have accelerating extended distributions of charge which produce no radiation fields. Ehrenfest was attempting to explain one of the most vexing problems of physics at the time: the presence of electrons in the atom. The atom was known to have electrons moving about within it, and these electrons should have been radiating constantly, according to the known physics of the time, but were not seen to do so.
Soon after Ehrenfest’s paper, Bohr produced his model of the atom, which eliminated the need for radiationless orbits and ended most speculation on atomic structure. Ehrenfest’s work was mostly forgotten, but other researchers independently discovered other radiationless motions of charges, and this research would lead eventually to more detailed studies of invisibility. One of the most important researchers on radiationless motions was G.A. Schott, who in 1933 produced a beautiful and amazing theoretical result* which we discuss in this post.
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Skulls in the Stars 