A West Virginia University physicist has created an exact mathematical formula to explain the gravitational wave signals that have been observed from colliding black holes, which serve as a key validation of Albert Einstein’s Theory of General Relativity.
While scientists usually interpret the signals from gravitational waves by comparing them to computer simulations, in 2019, Sean McWilliams offered a more accurate and efficient method for the calculations and interpretations.
“This new model can tell us what the signal from coalescing black holes looks like just before and while they are merging, whereas preexisting models could only really tell us what is happening well before or well after the merger occurred,” said McWilliams, an assistant professor in the Eberly College of Arts and Sciences. “Unfortunately, there is still a gap between where the old models stop being valid and where my model starts being valid.”
Einstein’s Theory of General Relativity predicts that space and time are intertwined and can be made to ripple when orbiting black holes disrupt them. These ripples, called gravitational waves, can shrink and stretch anything in their path, although the effect at the Earth is imperceptibly small and challenging to observe. The measurements of gravitational waves are becoming more precise with time, making the need for increasingly accurate and efficient waveform models critical for future discoveries about the Universe.
Since the observation of gravitational waves by the Laser Interferometer Gravitational Wave Observatory (LIGO) collaboration in 2015, McWilliams, also a LIGO member, has been searching for new ways to calculate the waveform produced by two merging black holes. Now, as a 2020 National Science Foundation CAREER Award recipient, he is working to bridge that gap.
“The first goal of my new project is to extend the techniques from my merger model to smoothly transition to the best available model for the earlier part of the signal,” McWilliams said. “Once we have a complete model for the whole evolution of any source, we will implement that model within the larger code infrastructure that LIGO uses, so that it can be applied to searches of real black hole data.”
As part of the project, McWilliams will also help update the West Virginia Science Public Outreach Team’s program, “The Invisible Universe.” The team trains undergraduate student ambassadors to visit K-12 schools across the state to promote STEM.
“‘The Invisible Universe’ program focuses on gravitational waves,” McWilliams said. “I plan to include more information about recent research developments and to make the material more accessible to a K-12 audience.”
He is also updating WVU’s “Celebrating Einstein” programming, a series of events held in 2017 that blended STEM and fine arts, to include a new dramatic production. The play will explore Albert Einstein’s famous thought experiments, such as the experiences a person would have as they fell from a roof or rode a light beam. It is expected to open in 2023.
“Through a combination of actor portrayal, projection and stage effects, and live music, we hope to engage the audience through sight and sound,” McWilliams said. “The play will be accompanied by a compilation of quotes, passages and audio clips from Einstein himself.”
McWilliams hopes this project will contribute to the developing field of gravitational wave astronomy, which is still a relatively new discipline.
“We are already beginning to have issues with our existing models, in the sense that the model inaccuracies are limiting the findings we are getting from newly discovered events. That is not ideal for what will ultimately be a multi-billion-dollar endeavor,” McWilliams said. “Our research project will hopefully address this issue.”