Lecture1-2

# Under this assumpcon a strong magnecc eld would eect

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Unformatted text preview: constant speed (if its velocity is nonzero). Newton: The laws of physics are the same in any inerCal frame. 12 Transform to a New InerCal Frame (Galilean TransformaCon) u༇ Subtract oﬀ the posiCon of the new origin in the old frame. o  O’ is at x=vt o  x’=x- vt u༇ Other coordinates unchanged o  y’=y o  z’=z o  t’=t 13 ElectromagneCc Theory Predicts Waves with Velocity c u༇ Maxwell’s equaCons have a travelling wave soluCon. u༇ Light, radio waves… were recognized to be EM waves. u༇ But in what frame is the velocity c? o  Ether (medium for EM waves) deﬁnes one rest frame for EM waves o  RelaCvity: laws of physics are independent of inerCal frame choice 14 Heaviside, Lorentz, Fitzgerald Working on Electrodynamics of moving bodies Oliver Heaviside (1850- 1925) was a telegrapher, but deafness forced him to reCre and devote himself to invesCgaCons of electricity. He became an eccentric recluse, befriended by FitzGerald and (by correspondence) by Hertz. In 1892 he introduced the operaConal calculus (Laplace transforms) to study transient currents in networks and theoreCcal aspects of problems in electrical transmission. In 1902, a^er wireless telegraphy proved eﬀecCve over long distances, Heaviside theorized that a conducCng layer of the atmosphere existed that allows radio waves to follow the Earth's curvature. He invented vector analysis and wrote Maxwell’s equaCons as we know them today. He showed how EM ﬁelds transformed to new inerCal frames. Hendrik Antoon Lorentz (1853- 1928), a professor of physics at the University of Leiden, sought to explain the origin of light by the oscillaCons of charged parCcles inside atoms. Under this assumpCon, a strong magneCc ﬁeld would eﬀect the wavelength. The observaCon of this eﬀect by his pupil, Zeeman, won a Nobel prize for 1902 for the pair. However, the Lorentz theory could not explain the results of the Michelson- Morley experiment. Inﬂuenced by the proposal of Fitzgerald, Lorentz arrived at the formulas known as the Lorentz transformaCons to describe the relaCon of mass, length and Cme for a moving body. These equaCons form the basis for Einstein's special theory of relaCvity. Einstein read Lorentz’s book George Francis FitzGerald (1851- 1901), a professor...
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