Dr. Carlos Lousto has always been captivated by space. A child of the space race growing up in South America, he remembers watching Neil Armstrong’s historic first step onto the moon. As he recalled, “This event triggered the imagination of a whole generation and made us feel that the secrets of the universe were reachable.” From that point on, he knew that studying space and its myriad of mysterious phenomena would be his life’s work.
Lousto earned his doctorates in Physics and Relativistic Astrophysics from the University of La Plata and the University of Buenos Aires respectively. Since then, he has spent nearly 20 years studying space and relativistic physics, specifically black holes. His work has taken him across the globe, from his childhood home in South America to Paris, France, Germany, Utah, Texas, and finally, a small office across the hall from a massive computer room at RIT’s Center for Computational Relativity and Gravitation (CCRG).
The Team and Their Tech
The team at the CCRG is made up of 20 researchers, who are a mix of professors and associate professors like Dr. Manuela Campanelli, the CCRG director; Dr. Yosef Zlochower and Lousto, as well as several grad students and even undergrads. Past students working with the CCRG have moved on to obtain their doctorates from prestigious universities such as Northwestern. The group got its start nearly a decade ago at the University of Texas at Brownsville (UTB). There, they made their initial 2005 breakthrough in modeling black hole collisions. Then in 2007, they packed up and moved to RIT, where they have made their most recent breakthroughs.
The team is based in the Laboratory for Applied Computing (LAC, 74), which is little more than a hallway between Thomas B. Golisano Hall (GOL, 70) and Louise Slaughter Hall (SLA, 78). But in this hallway rests the heart of the CCRG’s operations.
In a room with sleek glass walls sits the CCRG’s main simulation computer. This computational powerhouse, a beast three years in the making, consists of some 500 processing cores, 50 terabytes of hard drive storage and nearly 2 terabytes of RAM. To put that in perspective, today’s high-end personal computers typically have four processing cores and 8 gigabytes of RAM. In order to model the team’s most complicated simulations, this machine will run continually for up to three months straight.
A Cosmological Conundrum
Black holes have fascinated astronomers and sci-fi buffs for decades. To many, they hold an aura of mystique and mystery that few other astronomical phenomena could ever hope to garner. There is a kind of grim fascination to be found in an astronomical vacuum so powerful that not even light can escape its grasp. But now, the team at the CCRG are shining a light on the unseen.
In 2005, that team, at that time located at UTB, lead by Campanelli, Lousto and Zlochower, all from the School of Mathematical Sciences in the College of Science, made a breakthrough
discovery by using computer simulations to model the behavior of colliding black holes. That technique, known as moving punctures, allowed them to use much more accurate numerical
techniques in their models.
As it stands, there are two methods for calculating the behavior of black hole collisions. As Zlochower explains, “If the mass ratio is very, very small, it turns out that there are these approximation techniques that one can use that get you everything that you need … For large mass ratios, as you get closer to one, you can use what we call fully numerical techniques.” Although these techniques work successfully for specific mass ratios, there is a range in between for which neither of these methods is particularly accurate.
Illuminating the Blackness
Lousto and Zlochower’s most recent discovery may be the missing piece. Late last year, they were successfully able to modify their models to simulate the collision of two black holes with a mass ratio of 100-to-1, meaning that one black hole was 100 times larger than the other. As this ratio lies within the gap between the two modeling methods, their method may be a building block for eventually bridging that gap. Beyond that, it could be used to directly prove the existence of black holes.
When dealing with the numerical model, the work involved in calculating the result of a collision between two similarly sized black holes is relatively easy. Unfortunately, as the size discrepancy between them increases, the amount of work that the model’s calculation requires increases exponentially. What this means is that modeling two black holes whose masses were at ratios of 10-to-1 takes approximately 10,000 times more work than two similarly sized black holes. It had been generally accepted that it would take nearly five years, as well as further developments in computing power, to be able to calculate this model.
What the team managed to do, through clever manipulation of their computer models, was reduce the amount of work to somewhere between the mass ratio and the mass ratio squared. What that means is that that 10,000 times more work was now something closer to 10 to 100 times more work. “It still takes a lot of work, just not an astronomical amount of work, so it was something that was [more] feasible,” said Zlochower.
Beyond the Black
The computations done by CCRG are not only useful for modeling black hole collisions, but they can also be used to assist current gravitational wave detectors. The ultimate goal is to directly detect gravitational radiation and, in turn, black holes. “We are on the verge of detecting, for the first time, gravitational waves. When this happens, it will have a big impact on physics and astrophysics,” explained Lousto. “A Nobel Prize award is waiting for this first detection of gravitation waves and also of the direct confirmation of the existence of black holes.”
Super dense regions of space that create such a strong gravitational field that not even light can escape them. As of yet, there has been no direct proof that black holes exist. They are currently a theoretical construct predicted by general relativity.
A unique form of radiation that only appears when binary black holes orbit each other prior to colliding. As of yet, they have not been directly observed from Earth.
A comparison of the masses of any two given black holes. The smaller the number, the greater the discrepancy between the two masses. A mass ratio of 10-to-1 indicates that one black hole is 10 times heavier than the other.