Brian Greene, Columbia University physicist and co-founder of the World Science Festival, explains how today’s physicists and mathematicians use an Einsteinian formula to explain the universe that Einstein himself originally thought was false.

You can learn more fascinating science at this year’s 10th annual World Science Festival in NYC taking place from May 30-June 4. Following is a transcript of the video.

*The amazing thing is that blunder in Einstein’s mind is something that we now believe describes the actual universe.*

*Einstein became Einstein really because of his discovery of the general theory of relativity in 1915. The core of it are the Einstein field equations. And that’s a set of equations that relate the curvature of spacetime to the amount of matter and energy moving through a region of spacetime.*

*Interesting when Einstein applied theses equations to the entire universe, he found a result that he wasn’t happy with. He found that the universe could not be static and unchanging. It had to be either stretching or contracting.*

*And he said, “no.” The universe is clearly static and eternal. So what did he do? He went back to the equations.Put in one more term. On the left hand side he put in lambda. Lambda is what’s called the cosmological constant. He called it the cosmological member. And what it does is it can kind of give an outward push that can stabilise the inward pull of gravity, resulting in a static universe.And then Einstein was happy. Right?*

*But then in 1929 we learn that the universe is expanding and Einstein says,*

*Ugh, I wish I would not have put that term in.*

*Because my equations predicted that the universe is expanding and I would have gotten there 12 years before the observations. Today the amazing thing is that blunder in Einstein’s mind is something that we now believe describes the actual universe.*

*Because when we found that the accelerated expansion is happening, we want something that can push everything apart. What can do that?Einstein’s cosmological constant pushes things apart. We employ a different value.A different number than Einstein would have thought. But the idea is exactly what Einstein came up with.*

*Even Einstein’s bad ideas wind up being pretty darn good.*

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