NOVA

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Instructor

In 1915, Einstein published his groundbreaking theory of general relativity. According to his theory, space and time are intertwined. Together, they form a four-dimensional fabric called spacetime, and massive objects can warp that fabric. Now everything in the universe including light travels through space time. So if the gravity from a massive object warped spacetime the path that light travels in can seemingly bend. This blew people's minds. (mind exploding) Up until then, the concept of gravity came from Isaac Newton. In his worldview, space and time were absolute and independent. So Einstein's idea was really radical. The problem was there was no way to test his idea in the lab. His equations predicted that only a truly massive object could warp spacetime enough to make the light bending effect visible. Something as massive for example, as the sun. -

Sun

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Instructor

Luckily just four years after Einstein published his famous theory a total eclipse allowed an astronomer named sir Arthur Eddington to test it. The eclipse was going to occur just as the Sun was crossing a distance star cluster. Scientists knew where these stars normally appeared in the sky at night. If Einstein's idea was right, then when the massive Sun crossed in front of those stars it would warp spacetime, and shift the apparent position of the stars farther from the Sun. But usually the brightness of the Sun would make the stars impossible to see. During that solar eclipse, when the Moon blocked out the Sun's light, the stars were visible and Eddington measure the effect. -

Eddington

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Instructor

His experiment demonstrated that light curved as general relativity predicted leading Einstein down the path to stardom. (cameras clicking) (fans chattering) -

Instructor

Be sure to thank him for figuring out how the universe works as you watch the eclipse over America on August 21st. (light music)