On Sept. 14, 2015, an international team of scientists detected gravitational waves, opening a new realm of study in astrophysics. This was the first time that gravitational waves were empirically detected, 100 years after Albert Einstein predicted their existence. MSU physicist Neil Cornish was one of the members of this elite team of researchers.
Cornish has been a professor at MSU since August 1999. He previously worked in the field of theoretical cosmology, both at Cambridge as part of Stephen Hawking’s research group and also at Princeton on a NASA project to map afterglow of the big bang. He became interested in changing his focus to gravitational waves because of all the possibilities the field offered. “It’s opening up an entire new way of looking at the universe, the potential just seemed to be so great,” he said. “It was like wide open territory, like going out to the West and there were all these opportunities where it hadn’t all been picked over.”
MSU is one of few universities with a program in extreme gravity, which led Cornish to Montana. “There aren’t that many places in the world that actually have a focus on studying gravitational astrophysics and extreme gravity,” he said. The program was founded in the 1960s by Ken Nordtvedt, who came to MSU from MIT and established a group focused on gravity and general relativity, hiring new faculty in the field.
In addition to its research opportunities, Bozeman’s landscape appealed to Cornish. He grew up on a farm in the foothills of the Grampians in Australia, and he was happy to return to the mountains. “There was a department with a research focus in what I worked in also in a beautiful mountain setting, so it just seemed like the perfect fit,” he said.
In 2007 MSU became the 42nd institution to join the Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration, a project which uses high-sensitivity detectors to search for gravitational waves. The LIGO project started in 1997 and began installing advanced detectors in 2011. The new instruments began operation in 2015.
According to Cornish, collaboration on an international level is becoming increasingly common, especially in the field of astronomy. “To be able to go beyond what has been done previously in astronomy you typically need a bigger telescope, more sensitive equipment, and these facilities cost hundreds of millions to billions of dollars. They’re not something that a single researcher is going to be doing,” Cornish explained. “We’re definitely in the era of big science.”
Currently, two MSU researchers are working on the LIGO project: Cornish and graduate student Meg Millhouse, using a data analysis method developed by Cornish and former MSU graduate students Tyson Littenberg and Paul Baker. “We’ve developed a technique that allows us to detect any kind of gravitational wave signal with no assumptions about what it looks like,” Cornish said. Other data analysis methods use pattern matching, making this method a unique way to search for gravitational wave signals in the trace plots produced by the LIGO detectors, which use lasers to track the distance between two mirrors. By not making assumptions, the the analysis program can pick up even unexpected signals, as signals have not been modeled for all cosmic events. “It opens up discovery space,” Cornish said. The team’s work was featured in the first figure of the gravitational waves discovery paper.
In MSU’s extreme gravity group, there are three professors and eight graduate students doing research, as well as some undergraduate students. Only Cornish and Millhouse are officially members of the LIGO collaboration, but there are other research projects being done as well. Another one of Cornish’s projects is using pulsar timing to detect gravitational waves. This technique is meant to pick up lower frequency gravitational waves produced by larger cosmic events.
The department as a whole does not require many university resources; as the research is mostly theoretical, the department does not require laboratory space. They use MSU’s supercomputer —Hyalite Cluster— for some of their analysis, though most of the LIGO data analysis takes place on National Science Foundation-established supercomputers at CalTech. Cornish’s research is supported by three grants: two from the National Science Foundation (one for LIGO and one for pulsar timing), and one from NASA for the development of a future gravitational wave detector that would go in space. According to Cornish, while extreme gravity research does not require a lot of university resources, they would benefit from greater supercomputer capabilities on campus.
Cornish’s research extends into his teaching. For undergraduate courses, Cornish teaches through the Honors College, including the introductory physics sequence and Origins, a seminar focusing on the origins of life and the universe. “When I teach in undergraduate physics, I like to make connections to things that are going on in physics right now because balls rolling down inclined planes doesn’t really generate much excitement,” he said. Additionally, some of the analysis techniques used for gravitational waves are built into the final project for an undergraduate course on computational methods. “I like to bring as much of the research into the teaching as possible,” Cornish said. He also teaches graduate courses.
Cornish was confident that gravitational waves would be detected by the new LIGO instruments, but not necessarily during the first observing run. “I was a little surprised with just how quickly it all happened, but I was essentially 100 percent confident that the new instruments within the next couple years would make a detection,” he said. He expects that within the next few years, tens to hundreds of gravitational waves will be detected. “Then we can really start to do some serious astrophysics. You can do a fair amount with one event, but you really start doing the astrophysics when you have hundreds.”