Luis Lehner: Decoding the universe’s hidden messages

Luis Lehner learned early that the most interesting things are the ones you can’t quite see.

As a toddler in Argentina, he had a penchant for going into the kitchen (his family’s or anyone else’s) and pulling open all the drawers. 

He wasn’t trying to get into mischief. He wasn’t looking for anything in particular. He just needed to know what was tantalizingly out of sight.

“I would be opening drawers, just to try and understand or know what was in there that I couldn’t see otherwise,” he says. 

Lehner was born curious and he never outgrew it. 

Now, as a theoretical physicist, Lehner’s curiosity is sated by looking in the deepest, darkest corners of the universe and sleuthing the secrets waiting to be found. Fortunately, he’s working at the forefront of a field that is brimming with new discoveries. 

Lehner’s research focuses on extreme cosmic environments, where black holes and neutron stars collide with such gravitational ferocity that the shockwaves in spacetime can be measured by observatories on Earth. 

“We learn about our universe by detecting all possible messengers that we get,” he explains.

Through most of astronomy’s history, the only messenger available was light, first visible only to our eyes, then through ever-more sophisticated telescopes. 

Now, the messengers of the universe include neutrinos and gravitational waves that pass through everything in their path, carrying with them information from distant places that light can’t escape. 

Gravitational waves are ripples in spacetime, produced when massive objects like black holes and neutron stars collide. By the time the ensuing shockwaves reach Earth, they distort spacetime by less than the width of a proton, and yet physicists detected them for the first time in 2015.

“That was an amazing day,” Lehner says, recalling the morning that LIGO (the Laser Interferometer Gravitational-Wave Observatory) announced the indisputable detection of gravitational waves. 

“It was almost to the day of the hundredth anniversary of Einstein’s theory of relativity.” 

Lehner and dozens of colleagues watched the LIGO announcement live via webcast in Perimeter’s Black Hole Bistro, and joined them in cheers upon hearing the telltale “chirp” — the auditory representation of the two black holes colliding. 

For Lehner, the moment felt less like an answer than an opening. “That very first detection was like, I don’t know, a kid just being born,” he says. “It’s like thinking everything is possible from now on.”

Lehner first encountered Perimeter in 2001, just as the Institute was taking shape and long before gravitational waves had been detected. He was a postdoctoral researcher in British Columbia and visited Perimeter while it was still housed in its original building, a converted post office. The atmosphere appealed to him right away. 

“It was very family-oriented,” he recalls, “a very close-knit community of researchers going at full speed.”

His career took him elsewhere before it brought him back. After his postdoctoral work, Lehner moved to the United States, joining the faculty at Louisiana State University. He returned to Perimeter as faculty in 2009.

“I found myself just walking around talking with lots of people,” he says. “Researchers that in a typical setting I wouldn’t have had the chance to work with. Regardless of where people’s fields were, everyone was there, everyone was excited.”

Lehner now holds the Carlo Fidani Rainer Weiss Chair in Theoretical Physics at Perimeter, and his curiosity remains unabated. When he’s not unravelling physics mysteries, he likes to challenge his perspectives in new ways. He recently took up flying airplanes, where there is no room for abstractions or theoretical experiments. 

“Flying requires full focus,” he says. “Otherwise, you can risk your life.” 

Whether at the blackboard or the yoke, Lehner is propelled by the same fundamental force. 

“It’s the desire to learn,” he says. 

He’s not chasing recognition, or awards, or any end-point in particular. He just wants to spend every waking moment learning. 

“And sometimes when I’m sleeping,” he admits. “I dream about this.”