A hundred years ago, on May 29, 1919, Albert Einstein became the most famous scientist in the world, his name a synonym for genius.

In 1915, Einstein published his General Theory of Relativity, which argued that massive objects, such as the sun, distort space-time in much the same way as a bowling ball distorts a suspended rubber sheet. Thus, light moving past a massive object would appear to shift. This was a testable hypothesis. Background stars very near the sun should show a measurable shift in position. But special conditions were required. The sun is so bright that all background stars are lost in its glare, so the test could only be made during a total solar eclipse.

Amid World War I, there was little opportunity to go off to some strange part of the globe that happened to be in the path of an eclipse. But in 1919, with the war over, the very distinguished British astronomer Sir Arthur Eddington traveled to Principe, off the west coast of Africa and then a Portuguese colony to finally test Einstein’s hypothesis. And on May 29th, despite less than ideal weather conditions, but helped by the longest totality eclipse totality in 500 years, over six minutes, he was able to make the necessary observations. Eddington confirmed that the stars had shifted just as Einstein predicted. Sir Isaac Newton (“Nature and nature’s laws lay hid in night. God said, ‘Let Newton be’ and all was light.”) had been dethroned.

When the data was published the following year, it was front-page news all over the world. Einstein became a household name. His theory has been tested and confirmed thousands of times since. When his prediction of gravity waves was confirmed three years ago, the observation won a Nobel Prize.