How Eclipses Helped Newton and Einstein

1715 AD - Eclipses Prove Newton Right

By the 17th century, the moon's size and distance were well known but no one knew why the moon orbited Earth. Then a real oddball named Isaac Newton figured out The Law Of Gravity. But some people needed convincing.

Newton's hype man Edmund Halley (that guy they named a comet after) - said "OK, Newton's law of gravity determines the moon's orbit. So i should be able to use that law to predict exactly when the moon will go in front of the sun."

He calculated that an eclipse would hit Britain at 9:05 AM on May 3, 1715, and he printed up handy posters that reassured everyone no, the king isn't going to die. Haley got impressively close - the sun went dark at 9 sharp. And that eclipse proved Newton wasn't crazy, he was a genius!

1919 AD - Eclipse Prove Einstein Right

Einstein had this radical new theory called "The General Theory Of Relativity", and it made Vulcan unnecessary. According to the theory, Mercury was thrown off course because the sun's bulk was warping the very fabric of space time.

Einstein's equations predicted the wobbly orbit perfectly. But as always some people demanded more proof. And once again, an eclipse came in useful. In 1919, the darkened skies allowed scientists to see stars near the sun, and just as Einstein predicted, the sun's huge mass nudged the starlight off course. Those results made him an instant celebrity.