Carleton physicists play role in groundbreaking discovery

18 February 2016

Physics is having a rock star moment.

Carleton professor Nelson Christensen saw the flashing cameras firsthand after he and his colleagues from the scientific community announced their groundbreaking discovery of gravitational waves—the ripples in the fabric of space and time that Albert Einstein famously posited a century ago—at a Washington D.C. press conference last week.

[[img width=”350″ float=”right” caption=”Nelson Christensen”]]

The scientific collaboration used a $1.1 billion set of instruments known as the Laser Interferometer Gravitational-Wave Observatory, or LIGO, to detect a gravitational wave generated by the collision of two black holes. The resulting sound—a chirp that signaled “one of the biggest eureka moments in the history of physics”—was logged on September 14, 2015.

As Christensen and his fellow invited scientists stood among a crowd of eager reporters inside the National Press Club, the four main LIGO speakers on the dais appeared from behind closed doors. The eruption that followed transformed a potentially exciting snapshot into “Woodstock for physicists.”

“It was like the Rolling Stones walked out,” Christensen says, beaming. “Everyone’s heads turned.”

[[img width=”400″ float=”left” caption=”Jialun Luo ’16″]]

More than 1,000 scientists contributed to the verified discovery paper in the Physical Review Letters journal, including five Carleton alumni and two current students: Nathaniel Strauss ’16 (Holmen, Wis.) and Jialun Luo ’16 (Guangzhou, China). Christensen led the Carleton research team, while Strauss and Luo were promoted to full authorship after cleaning up noise data and automating various processes related to the breakthrough.

[[img width=”400″ float=”left” caption=”Nathaniel Strauss ’16″]]

“This is really the first research that I’ve been part of as a physics student, so I feel tremendously lucky to both be at Carleton and to work with Nelson,” Strauss says. “It’s such a wonderful opportunity to have had this kind of experience so early in my career.”

LIGO, built by Caltech and MIT with observatories funded by the National Science Foundation, is comprised of scientists from around the world. Carleton joined the collaboration in 1999.

Christensen’s involvement stretches back further, to his undergrad days at Stanford in the early ‘80s. Sharing in the moment some 30 years later as a Carleton professor was almost too much to take in.

“One of the reasons why the result was so emotional on September 14 is that I didn’t believe this was a real event,” Christensen says. “As the day rolled on, the evidence that this was (a mistake) just crumbled away. I woke up at 6 a.m. (the next day) and read the latest updates. Then I went for my run that I do every morning, and I got to the middle of Sechler Park, and I stopped and started shaking. I realized, ‘This is it.’”

“It” is the long-awaited confirmation of gravitational waves as part of Einstein’s theory of general relativity. When massive objects like black holes collide, they generate gravitational waves that stretch space-time, completing the Nobel Prize winning physicist’s vision of a universe in which “space and time are interwoven and dynamic, able to stretch, shrink, and jiggle.”

Scientists have been studying these waves for decades—including Carleton physics professor Joel Weisberg, whose research has been continuously funded by the National Science Foundation since 1987—but until now, there hadn’t been that chirp.

“A lot of it is providing potential for future scientific discovery. Up until now, a lot of astronomical observations we’ve made are basically from different forms of light coming in from outer space,” says Strauss, a physics major who is applying to graduate schools.

“Now that we can detect gravitational waves, it’s a whole different phenomenon. It’s a whole different way of looking at the sky.”

With 1,004 people named as co-authors of the paper—everyone from wide-eyed undergrads to some of the most accomplished scientists in the world—the collaboration proved “difficult … but not impossible,” Christensen says.

The Carleton roll call alone is impressive. Alumni who contributed include Tom Callister ’13 (Caltech), Santiago Caride ’08 (Texas Tech), Michael Coughlin ’12 (Harvard), Tomoki Isogai ’10 (MIT), and Adam Libson ’04 (MIT). Current students Jacob Broida ’17 (Cleveland), Yuping Huang ’17 (Shantou, Guandong, China), Emily Phillips Longley ’16 (St. Paul, Minn.), and Max Rohde ’17 (Arlington Heights, Ill.) are also working on LIGO research and its companion papers.

[[img width=”400″ float=”left” caption=”Emily Phillips Longley ’16”]]

The expansive cohort used e-mails, Wikis, logbooks, and online work groups to keep everyone apprised of the latest results. Working with experienced LIGO scientists was intimidating, Strauss says, but being able to “learn the ropes” as an undergrad confirms the trust Christensen put in his young protégés. 

There isn’t a Carleton secret, Christensen says. Thanks to the liberal arts ethos, Carleton prepares students in all fields to write and communicate effectively. Beyond the research, there’s an emphasis on a burgeoning physicist’s ability to tell—and sell—the story of science.

“How do you get a billion dollars in funding from the government? You have to know the science, but you also have to communicate its purpose. I think our students do that very well,” Christensen says.

“I can’t tell you the number of times someone in the collaboration said to me, ‘Hey that graduate student of yours is really productive.’ And I’d have to say to them, ‘Yeah, that’s not a graduate student. That’s an undergrad.’”

Edited video of Carleton’s press conference announcing its involvement in the LIGO Research Collaboration discovery from February 11, 2016.