LIGO's first direct detection of gravitational waves captured the signal of two black holes merging. Krishna Choudhary and Lester Nare discuss how laser interferometers detect extraordinarily small changes in distance and why this measurement opened another way to observe the universe. The segment connects a prediction of general relativity with the engineering needed to test it.
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LIGO compares light traveling along perpendicular arms to detect tiny distance changes.
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Its first direct detection came from a binary black hole merger in 2015.
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Gravitational waves carry information that complements observations using light.
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2:06:30that's replicated this feat at a scale that can be used for uh commercial uh reusability. >> Yeah. Yeah. And I mean now we take it for granted but like dude at the time >> it was insane. No one thought it was potent. Everyone was like, "This is ridiculous." >> Oh, like NASA's been trying for a while. Actually, no. It's it's like, you know, with modern computing now and the modern hardware and the fast feedback between control systems and how you can like point the rocket booster and things like that made it possible. It's amazing. >> Still not replicated, so it's not that trivial. 2015, uh, one of my favorite instruments, uh, the detection first detection of gravitational first direct detection of gravitational waves. Yeah,
2:07:11this is 20 years in the making. I talked about how we failed at the superconducting super collider. That was a wakeup call for science in America. They decided to start doing big projects, high risk, high reward. This was the highest risk because no one thought it was possible. I mean you have to measure the difference in the length of uh a leg of your detector that is 4 km long by something like 10 -8 m. Right? So it's like an atom is 10 theus 10. You've got to go an atom within an atom and measure that tiny difference in order to measure gravitational waves. We had already discovered gravitational
2:07:52waves kind of with the Taylor Hulse um binary pulsar where we had shown that obviously gravitational waves were permeating out of the binary pulsar. >> That was an indirect >> but it was indirect. This we're literally measuring a gravitational wave move through space and time and distort the length and the timing of photons traveling in tunnels. Um there are two observatories now, one in Washington state and one in Louisiana. The LIGO collaboration detected two black holes colliding, spiraling together and forming one big black hole that shown with enough energy that was brighter than all of the stars in the universe
2:08:34combined. Um, Rainer Weiss, Barry Beerish, Kip Thorne, they won the 2017 Nobel Prize in physics basically two years after this because everyone was like "Holy >> holy, you know what?" because that >> I can't believe you did it. I can't believe you actually >> I can't believe you've done this. >> Yeah. Um it's it's absolutely amazing. We have a deep dive into the LIGO discovery and all of the shenanigans and drama that went into it. >> The posttocks on the on the top. People thought they were driving around. It's a great it's a great deep dive. Definitely check it out. We are getting very close to the conclusion of our list. We have four more left. We are in 2017
2:09:16the invention of the transformer architecture. >> Yes, this is a team of researchers at Google brain in the Bay Area. They publish attention is all you need. It's a paper that has a banger title and it introduces it introduces the transformer deep learning architecture that's based on this self-attention mechanism. Um