1. Starlight bends — but how much?
Einstein performed a series of calculations to determine the size of the predicted shift but initially muffed the effort, arriving at a number that was half the correct value.
Had the astronomers managed to test this number in their initial eclipse-viewing efforts, their observations wouldn’t have matched his prediction. But their attempts were stymied by weather in 1912 and by war in 1914. By the time they made the necessary observation, in the spring of 1919, Einstein had corrected his blunder — and astronomers saw exactly the shift that he had predicted.
2. Gravitational waves don’t exist — or do they?
Einstein moved on to other problems. When he returned to it two decades later, he concluded that gravitational waves couldn’t exist because they’d create “singularities” — regions in which space and time are stretched to infinity.
Einstein had goofed because of the mathematical coordinate system he used to tackle the problem. It's a bit like what happens with the latitude and longitude used to track positions on Earth... It works in most places on the planet. But as one gets close to the poles, lines of longitude converge and the system breaks down.
3. Einstein and the expanding universe
Einstein was uncomfortable with some of relativity’s implications, including one of the biggest — that the universe isn’t a static thing but an entity that must expand or contract. This was unthinkable to Einstein, who believed the universe existed in a “steady state.”
So Einstein added a fudge factor to his equations, a kind of energy associated with empty space. This cosmological constant allowed for a stable universe. But sure enough, astronomers in the 1920s confirmed that the universe was expanding. Einstein later called the cosmological constant the “greatest blunder” of his career.
(Excerpt) Read more at nbcnews.com ...
