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Bringing Black Holes Down to Earth

Physicist Pierre Christian, PhD, is a leader in the study of the laws of the universe.

by Alan Bisbort

What is 6.5 billion times more massive than the sun and, conversely, a “relatively tiny astronomical object”?

This is not a trick question, at least not to Fairfield University’s Pierre Christian, PhD, assistant professor of physics in the College of Arts and Sciences. Dr. Christian was part of the Event Horizon Telescope project (EHT) that, in April 2019, captured the first resolved images of a black hole (the answer to the above question)—a feat that was thought impossible just a generation ago.

The black hole in question, Messier 87 (M87), is located 55 light years from Earth in the “nearby” Virgo galaxy cluster. In order to capture this most elusive of entities visually, scientists affiliated with EHT utilized a series of nine interlocking radio telescopes to, in essence, create a virtual telescope as large as planet Earth.

“We saw many iterations of the black hole before the final image was released, so by then we’d experienced that thrill many times,” said Dr. Christian. “But even for scientists, it was exciting, especially the senior members of the research staff, some of whom have spent 50 or 60 years researching and theorizing about black holes before finally getting to see one. It is overwhelming for them.”

Dr. Christian joined the EHT project while conducting post-doctoral research at the University of Arizona, and he has brought the affiliation and knowledge with him to Fairfield University, where he began teaching undergraduate physics courses in 2021.

His interest in black holes is linked to his groundbreaking research into gravity. He’s one of four lead authors of important, newly published research on testing gravity “with the Shadow of the M87 Black Hole.” Using the massive datasets collected from the EHT project, he has created algorithms to compare black hole theories with the EHT results and then to use the findings to test theories of gravity.

“Gravity is the least understood of the fundamental forces in the universe, the last bastion of the great unknown in physics,” said Dr. Christian, who earned his master’s and PhD in astrophysics at Harvard. “I’m using black holes as a way to test our understanding of gravity, because a black hole is a gravitational object so strong that light can’t escape from it.”

Gravity on Earth, he explained, is too weak for proper experimentation, pointing to the fact that a person can pick up a paperclip with a magnet.

“This shows that gravity on Earth is much weaker than electromagnetism, another fundamental force in the universe,” he said. “You need something strong like a black hole to research gravity properly. But how do you get a black hole?”

That’s where his present research comes into play. Currently, two undergraduate assistants, Charlie Olson ’25 and Tim Holewienko ’24, are working with Dr. Christian to create a virtual-reality version of a black hole using computer simulations.

“This is not chemistry where you can do lab experiments, add this to that and then heat it and so on,” said Dr. Christian with a laugh. “But experimentation is the cornerstone of science. You have a theory and you test it through experiments. With a black hole, we can’t do that. It’s too far away and we are stuck here on Earth! So we are creating a tabletop simulation that we want to bring to the classroom at Fairfield.” To illustrate the denseness of a black hole, Dr. Christian offers a thought experiment. “Imagine that you have 6.5 billion times the mass of the sun in apples,” he said. “They will take up a huge amount of volume in space, right? Now imagine you have 6.5 billion times the mass of the sun in steel. It will take up far less volume in space because steel is so dense. You keep going smaller with more dense objects until you get to a black hole, which is the densest object we know of in the universe.” Dr. Christian estimates that the black hole simulator is about half-completed. “We’ll be working on it over the summer, so we will see,” he said. “But next year we will definitely have a course on gravity and spacetime where physics students can learn about black holes in Bannow Science Center classrooms and labs.”

Fairfield is Dr. Christian’s first teaching job, and he is enjoying the experience. “I had always been at big schools, and I like that Fairfield is a smaller liberal arts university,” he said. “Here we know each other on the faculty. You know the person in the office next door and down the hall, not just in physics, but in engineering and math; we are closely connected. It’s the same with the students. We say hello when we see each other on campus. That’s been really nice.” l F

Left: An enhanced image of a black hole with nebula over stars and cloud fields in outer space. Above: Dr. Pierre Christian, assistant professor of physics, working with students in a Bannow Science Center classroom.

“You have a theory and you test it through experiments. With a black hole, we can’t do that. It’s too far away and we are stuck here on Earth! So we are creating a tabletop simulation that we want to bring to the classroom at Fairfield.”

Dr. Pierre Christian, Assistant Professor of Physics