A gravitational wave is a very slight stretching in one dimension. RW: The equations don’t tell you much until you put actual numbers into them and you find out how much energy is involved in making a distortion of space. It’s quite another thing to build giant L-shaped instruments that span four kilometers on two coasts. It’s one thing to say, “Oh, two black holes are going to collide,” and work it out on paper. I think that’s why I became so enamored of the physicality of the LIGO experiment. These waves, which move at the speed of light, are created when massive bodies accelerate through space and time. His theory also predicted the existence of gravitational waves, which are ripples in space and time.
As Albert Einstein demonstrated in his theory of general relativity, the gravity of massive bodies warps the fabric of space and time-and those bodies move along paths determined by this geometry. How our sun and Earth warp space and time, or spacetime, is represented here with a green grid. I would’ve loved to have seen Einstein’s face if he were presented with the data that we actually discovered such a thing, because he himself probably didn’t believe in much of it. The whole idea of gravity curling up space, that is the epitome of what is going on in a black hole. It’s the one thing that is so Einsteinian, we couldn’t have gotten it any other way. Rai Weiss: What was behind that statement - it is slightly facetious, of course - but you have to understand what black holes ultimately mean to people, and what they mean to the theory of gravity that Einstein put together. In August 2015, Rai and I were talking and he said - this after the experiment cost a billion dollars, people had spent 50 years building it - he said, “If we don’t detect black holes, the thing is a failure.” I thought that was a really bold thing to say on the eve of starting the detection, because most people in the scientific community did not think we would detect black holes, at least not for a long time. The detection happened in September 2015. So it was really an astronomical discovery as well. That was the first time we detected a pair of black holes, because they’re dark and we can’t see them with telescopes. The success of the experiment was not only the detection of gravitational waves. Janna Levin: The first detection made with LIGO was of a pair of black holes that collided 1.3 billion years ago. An edited version of the discussion follows. In a sparkling conversation held at a Brooklyn art space, Pioneer Works, Levin and Weiss (with help from journalist John Hockenberry) talked about how they work, how LIGO works - and the moment when they realized Einstein had just been proven right. Earlier this week, the LIGO team announced that on December 26, 2015, they had detected another rippling, spacetime-stretching gravitational wave that erupted 1.4 billion years ago when two other black holes collided at half the speed of light. Weiss was part of the group that designed and built LIGO, the detector that, in September 2015, for the first time “heard” the sound of two black holes crashing into one another, producing a gravitational wave that stretched spacetime and proving something that Einstein first floated as a theory almost 100 years ago.
WAS EINSTEIN A SPACE PIONEER HOW TO
Rainer Weiss, or Rai, as he’s known, is an experimental physicist - he thinks about how to find and measure something that may or may not exist outside of theory. Janna Levin is a theoretical physicist - she works with pen and paper to turn the elegant rules of the universe into theory (and also uses that pen and paper to write books about science her latest, Black Hole Blues, was recently published by Alfred A. Henze How do you build a real-world machine to test the most abstract of theories? Janna Levin talks with Rainer Weiss, one of the designers of LIGO, the four-km-long instrument that can detect the distant reverberations of two black holes crashing into one another. Simulation of merging black holes radiating gravitational waves.
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