There are precision measurements, and then there’s the Laser Interferometer Gravitational-Wave Observatory. In each of LIGO’s twin gravitational wave detectors (one in Hanford, Washington, and the other in Livingston, Louisiana), laser beams bounce back and forth down the four-kilometer arms of a giant L. When a gravitational wave passes through, the length of one arm changes relative to the other by less than the width of a proton. It’s by measuring these minuscule differences — a sensitivity akin to sensing the distance to the star Alpha Centauri down to the width of a human hair — that discoveries are made.
The design of the machine was decades in the making, as physicists needed to push every aspect to its absolute physical limits. Construction began in 1994 and took more than 20 years, including a four-year shutdown to improve the detectors, before LIGO detected its first gravitational wave in 2015: a ripple in the space-time fabric coming from the faraway collision of a pair of black holes.
Physicist Rana Adhikari led the detector optimization team in the mid-2000s. He and a handful of collaborators painstakingly honed parts of the LIGO design, exploring the contours of every limit that stood in the way of a more sensitive machine.
But after the 2015 detection, Adhikari wanted to see if they could improve upon LIGO’s design, enabling it, for instance, to pick up gravitational waves in a broader band of frequencies. Such an improvement would enable LIGO to see merging black holes of different sizes, as well as potential surprises. “What we’d really like to discover is the wild new astrophysical thing no one has imagined,” Adhikari said. “We should have no prejudice about what the universe makes.”
He and his team turned to AI. Initially, the AI’s designs seemed outlandish. “The outputs that the thing was giving us were really not comprehensible by people,” Adhikari said. “They were too complicated, and they looked like alien things or AI things. Just nothing that a human being would make, because it had no sense of symmetry, beauty, anything. It was just a mess.” But the design was clearly effective.
Quanta Magazine
There are precision measurements, and then there’s the Laser Interferometer Gravitational-Wave Observatory. In each of LIGO’s twin gravitational wave detectors (one in Hanford, Washington, and the other in Livingston, Louisiana), laser beams bounce back and forth down the four-kilometer arms of a giant L. When a gravitational wave passes through, the length of one arm changes relative to the other by less than the width of a proton. It’s by measuring these minuscule differences — a sensitivity akin to sensing the distance to the star Alpha Centauri down to the width of a human hair — that discoveries are made.
The design of the machine was decades in the making, as physicists needed to push every aspect to its absolute physical limits. Construction began in 1994 and took more than 20 years, including a four-year shutdown to improve the detectors, before LIGO detected its first gravitational wave in 2015: a ripple in the space-time fabric coming from the faraway collision of a pair of black holes.
Physicist Rana Adhikari led the detector optimization team in the mid-2000s. He and a handful of collaborators painstakingly honed parts of the LIGO design, exploring the contours of every limit that stood in the way of a more sensitive machine.
But after the 2015 detection, Adhikari wanted to see if they could improve upon LIGO’s design, enabling it, for instance, to pick up gravitational waves in a broader band of frequencies. Such an improvement would enable LIGO to see merging black holes of different sizes, as well as potential surprises. “What we’d really like to discover is the wild new astrophysical thing no one has imagined,” Adhikari said. “We should have no prejudice about what the universe makes.”
He and his team turned to AI. Initially, the AI’s designs seemed outlandish. “The outputs that the thing was giving us were really not comprehensible by people,” Adhikari said. “They were too complicated, and they looked like alien things or AI things. Just nothing that a human being would make, because it had no sense of symmetry, beauty, anything. It was just a mess.” But the design was clearly effective.
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🎨 1, 3: Señor Salme for Quanta Magazine
📸 2: Steve Babuljak
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