Closing Plenary Focuses on Gravitational Waves
Sigma Pi Sigma Physics Congress (PhysCon)
November 3, 2016 to November 5, 2016
San Francisco, CAMeeting host: By:
Chunyang Ding, Suryabrata Dutta, and Mehmet Tuna UysalSPS Chapter:
Gravitational waves made a big splash at the 2016 SPS Quadrennial Physics Congress. Dr. Patrick Brady, the Director of the Center for Gravitation, Cosmology and Astrophysics and a professor at the University of Wisconsin, Milwaukee, presented the fundamental discovery of gravitational waves as the final plenary talk of 2016 SPS Quadrennial Physics Congress. Over 1,200 undergraduate physics students listened to Dr. Brady speak on the scientific discovery,the people behind it, and the future of LIGO, as PhysCon concluded on November 5th, 2016.
The detection of gravitational waves from the collision of two thirty-solar-mass black holes made international headlines when it was announced, confirming one of the fundamental predictions of Einstein's theory of gravitation at a level of precision never achieved by humans. With a detection accuracy of one part in one thousand thousand thousand million, the Laser Interferometer Gravitational-Wave Observatory (LIGO) collaboration showed the "chirp" of two black holes—roughly 1.3 billion light years away from Earth—merging together. Dr. Brady, director of the LIGO collaboration from 2004-2006, has been working with LIGO since his graduate years at Caltech.
Before the talk and throughout the weekend, several plenary speakers alluded to how gravitational waves would soon transform both experimental and theoretical physics, including Dr. James Gates, Dr. Neil Turok, and Dr. Jocelyn Bell Burnell. "I've followed gravitational wave research for 45 years, knew it would be difficult to detect. I wasn't sure it would happen in my lifetime; I'm delighted it has," said Dr. Burnell, the honorary Congress chair of PhysCon 2016. She discovered pulsar stars, or rapidly rotating magnetized neutron stars, in 1967, which were used to indirectly measure gravitational waves by Joseph Taylor and Russell Hulse in 1974. For that effort, Taylor and Hulse received the 1993 Nobel award in physics.
Many undergraduate students shared the same excitement as Dr. Burnell, eagerly awaiting the closing plenary. "I'm hoping that [Dr. Brady] brings a lot of hype to the idea of gravitational waves. A lot of people here feel excited about studying gravitational waves," said Nathaniel Moore, a junior at the College of Wooster. Many undergraduates had already heard about gravitational waves, whether through the news coverage or through their undergraduate physics classes.
The detection of gravitational waves has been heralded as one of the most profound discoveries of the decade. Gravitational waves were first predicted by Einstein's theory of gravity as energy that dissipates through accelerating masses, but even Einstein thought they would remain forever undetected. The difficulty in detecting a gravitational wave is due to how weak it is; detecting the gravitational waves from a black hole merger event requires precision equivalent to measuring the distance from Earth to the star Alpha Centauri down to the width of a single human hair. To perform this ultra-precise detection, physicists Rainier Weiss of MIT, Kip Thorne of Caltech and Ronald Drever of Caltech designed a laser interferometer, something that can measure tiny disturbances using laser interference patterns. While simple in principle, the actual instrumentsÍone in Hanford, Washington, the other in Livingston, Louisiana—have arms stretching out four kilometers. Since the first two successful detections of gravitational waves, the LIGO collaboration has plans to build more laser interferometers in India, Japan, and Europe.
Through the talk, Dr. Brady provided an in-depth exploration of the science that led up to the detection of the gravitational wave on September 14, 2015, paralleling the timeline of human events with the approximate location of the gravitational wave at different points in time. Since the gravitational wave originated far away and 1.3 billion years ago, we could calculate where in the universe the wave was at any time. Dr. Brady pointed out that as humanity first began to use stone tools 2.5 million years ago, the gravitational wave was passing through the Andromeda galaxy; as Newton first described gravity 329 years ago, the wave had passed by the Pleiades; as the advanced LIGO project was coming online, the gravitational wave had already entered our solar system.
Dr. Brady spoke at length about the many physicists whose research was instrumental towards this detection, showing that physics is a huge collaborative effort. Of course, Dr. Brady is very familiar with large collaborations, having led the LIGO collaboration of a thousand scientists across 80 institutions and 15 countries from 2002 to 2004. Throughout the plenary and while answering student questions, Dr. Brady frequently returned to the human aspect of the research, encouraging the crowd of young scientists to pursue their dreams, whatever they were. But even though Dr. Brady could have a claim to be one of the leaders of this discovery, he remained humble. "I feel really lucky that I got the chance to be part of the team," said Dr. Brady, after being asked how it felt to be part of this discovery.
Although the plenary was focused on the technical aspects of LIGO, Dr. Brady often returned to the human aspect of scientific discovery. He peppered the history of the great physicists of the 20th century with remarks from his own childhood, and frequently nodded to the previous speeches given at PhysCon, especially to Dr. Jocelyn Bell Burnell and Dr. Persis Drell, for their remarks on diversity. In the closing minutes of the plenary, Dr. Brady charged all students to seek out diverse collaborations throughout the future of our research, stating that diversity improves the team. "This isn't about us as individuals. This is about us a us a group, this is about us as a society," he said, receiving thunderous applause from the audience. Dr. Brady also especially thanked many of the women who worked with him, a point that was not lost on students. "I really like the fact that he personally thanked every single woman on his team," said Hamna Ali, a physics major concentrating in astronomy at Towson University. "It was good to see that recognized. Even when his talk was almost entirely scientific, he still hit home on the fact that the community was important to him."
The future is bright for gravitational wave detection, opening a new spectrum for fundamental physics and astronomy observations. The detection of large black hole merger events, as opposed to neutron star mergers, is already shaking up our understanding of black holes. In addition, these newly detected black holes are the largest black holes ever detected, showing that there might be large classes of black holes that have previously been hidden. “It's opening up a whole new spectrum, providing a massive new opportunity for studying the universe," said Dr. Burnell. As the new LIGO sites come online, they will provide more and more of these opportunities to students of physics around the world.
Throughout the 2016 PhysCon, students have been challenged and encouraged by the speakers to be creative thinkers passionate about solving physics mysteries. Hearing from the scientists making the breakthroughs was highly encouraging for the students to continue pursuing a degree in physics. However, Dr. Brady believes that students should have time to explore all topics. “My opinion is that there is lots and lots of interesting things to do and to learn in this world,” said Dr. Brady. "Don't latch onto one too early. Realize that you have options, and when you are doing one, focus on it, and you'll do well."