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Unformatted text preview: MIT OpenCourseWare http://ocw.mit.edu 6.055J / 2.038J The Art of Approximation in Science and Engineering Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms . 66 6.055 / Art of approximation Large lenses warp and crack; one of the largest lenses made is 6 m. So there is no chance of detecting an angle of 10 − 9 . Physicists therefore searched for another source of light bending. In the solar system, the largest mass is the sun. At the surface of the sun, the field strength is Gm 6 . 7 · 10 − 11 m 3 s − 2 kg − 1 × 2 . 0 · 10 30 kg 10 − 6 ≈ . 4 00 . rc 2 ∼ 7 . 0 10 8 m × 3 . 0 10 8 m s − 1 × 3 . 0 10 8 m s − 1 ∼ 2 . 1 · · · · This angle, though small, is possible to detect: The required lens diameter is roughly d ∼ λ/θ ∼ . 5 · 10 − 6 m ∼ 20 cm . 2 . 1 10 − 6 · The eclipse expedition of 1919, led by Arthur Eddington of Cambridge, tried to measure exactly this effect. For many years Einstein believed that his theory of gravity would predict the Newton ian value, which turns out to be . 87 arcseconds for light just grazing the surface of the sun. The German mathematician, Soldner, derived the same result in 1803. Fortunately for Einstein’s reputation, the eclipse expeditions that went to test his (and Soldner’s) pre diction got rained or clouded out. By the time an expedition got lucky with the weather (Eddington’s in 1919), Einstein had invented a new theory of gravity, which predicted...
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This note was uploaded on 02/24/2012 for the course MECHANICAL 6.055J taught by Professor Sanjoymahajan during the Spring '08 term at MIT.
 Spring '08
 SanjoyMahajan

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