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Are you insatiably curious about the mysteries of the universe?

So was Albert Einstein.

In 1915, the then unknown theoretical physicist introduced a groundbreaking idea to the world: he suggested that space is not “inert,” but that the momentum of objects, or energy, in combination with gravity fields cause it to bend and shift. He called it the Theory of General Relativity.

The scientific community was naturally skeptical. The reigning theory had been put forward 228 years before, in 1687, by none other than Sir Isaac Newton. But Einstein felt that the legendary Englishman had missed an important factor in the essential equation: time.

Einstein believed that space combined with time to create a universe-wide “fabric” he referred to as the “space-time” continuum. As a result, when objects traveled through this fabric, he felt that gravitational fields would cause space and time to warp.


Following this prediction, the light of a distant star did not travel in a perfectly straight line, as Newton posited, but would bend when it came into contact with the gravitational field of an object with mass. Imagine the shape made by a person standing on a trampoline, and you’ve got the picture of the effect Einstein called a gravity well.

The hard part was proving this hypothesis.

For one thing, at the time of Einstein’s breakthrough, Europe was embroiled in World War I. For another, it required enormous planetary objects to move into alignment. Finally, that alignment had to be observed…and measured.

Fortunately, a British astronomer named Sir Arthur Eddington was paying attention. He worked out that as the sun is the most massive object in our solar system, its curvature of space-time would be noticeable from Earth when the moon orbits directly in front of the sun during a total solar eclipse. If the positions of neighboring stars could be precisely measured, then compared with their normal positions in the sky, he argued, and if the position of the stars were altered in the way that Einstein's theory predicted, the effects of warped space-time could be observed.

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Eddington's Experiment

At Eddington’s urging, the British Royal Astronomical Society organized expeditions to the tropics of Brazil and the island of Principe, off the west coast of Africa, where they believed the eclipse would be most visible. As it happened, the period of totality (the length of time that the moon blocks out all of the sun's surface) during the 1919 eclipse was one of the longest in recorded history, spanning roughly 6 minutes. This proved sufficient time to measure the relative locations of stars in the Hyades cluster usefully located at that time near the sun.

Eddington analyzed the observations from Brazil and Principe and proclaimed that the warping of space-time by the sun's mass was found to be real, thus turning the view of the Newtonian universe on its head. Some say Eddington was a fraud and fudged the results. Others call these naysayers anti-Semitic – Einstein was Jewish after all. Still others say the experiment and its fabulously successful results were an act of politically motivated theater. In Stephen Hawking’s words: “This proof of a German theory by British scientists was hailed as a great act of reconciliation between the two countries after the war.” But when the New York Times published the news on Nov. 7, 1919, Einstein became an instant celebrity, known to scientists and non-scientists alike.

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Since that most important eclipse 98 years ago, general relativity has been tested, and tested again, each time proving that Einstein’s space-time continuum is alive and well in the universe.

On 21 Aug, 2017, a total solar eclipse dazzled the continental U.S., from Oregon to South Carolina. It was a stellar (or interstellar) opportunity to revisit the experiment that confirmed Albert Einstein's Theory of General Relativity -- an intellectual breakthrough that would change our view of the universe forever, become the current description of gravitation in modern physics, and bring us such tools, like GPS, that we benefit from every day.

Einstein is perhaps the most famous and beloved scientist of all time. In addition to relativity theory, he also gave us quantum mechanics and thermodynamics. But we revere him not just for his scientific genius, he was also as a moral and even spiritual sage. That's why he's a Time Traveler Tours #HistoryHero.

Who's your #HistoryHero?

Tell us in the comments below and we'll let you know when we feature him or her on this blog.