New book traces expeditions to test Einstein's theory of relativity

phys.org | 5/29/2009 | Staff
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No Shadow of a Doubt, a new book by Daniel Kennefick, associate professor of physics at the University of Arkansas, tells the story of two research teams, organized by Arthur Stanley Eddington and Sir Frank Watson Dyson, who tested Einstein's theory of relativity. These expeditions traveled to Brazil and Africa to collect images of stars during the 1919 eclipse, and their results confirmed and brought mainstream attention to the theory.

"Einstein was a well-known scientist before, but this made him a celebrity," said Kennefick.

Einstein - Theory - Relativity - Way - Gravity

Einstein's theory of relativity proposed a new way of looking at gravity. The prevailing theory at the time, Newton's law of universal gravitation, described gravity as a force between massive objects. According to physicists in 1900, starlight, which they thought had no mass, would not be affected by gravity.

Einstein contradicted this expectation twice. First he showed, through his famous equation E=mc2, that light has mass, since it clearly has energy, and therefore should be affected by gravity. Then he theorized that gravity actually causes a curving of spacetime. According to his theory, light would follow this curve, so it would be affected by gravity, whether or not it had mass. If Einstein were to be correct, starlight traveling past the sun would follow a curved path as it traveled to Earth.

Someone - Earth - Star - Night

So if someone on Earth viewed a star during the night, when they were facing...
(Excerpt) Read more at: phys.org
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