Like ripples across a vast and dark pond, Albert Einstein predicted gravitational waves would, literally, rock our world. These energy pulses, caused by massive objects like black holes interacting with each other, would stretch and contract the very essence of the universe—the fabric of space-time. That was the prediction, but even Einstein doubted we mortals could build equipment sensitive enough to detect these undulations. This week, however, scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) report in the journal Physical Review Letters that the highly sensitive interferometers they operate in the U.S. and Europe have, in fact, detected the faint ripples from the dance of merging black holes over a billion years ago.
Dr. Christopher Orban, who teaches physics at The Ohio State University at Marion, is excited about the vistas that open up because of the LIGO discovery. “I can tell you that everybody in Ohio State’s astronomy department couldn’t be more thrilled about this. It is quite an amazing discovery.”
It is only recently that the laser and mirror technology used to detect gravitational waves has evolved in sensitivity enough that it can measure changes in length of less than with width of an atom. It is those minute changes that are caused by the billion year old gravitational wave washing across our spot in space-time.
Dr. Orban notes that, following Einstein’s thought experiment, it took until 2005 for astrophysicists to see some circumstantial evidence of gravitational waves. Astronomers observed two neutron stars circling each other, said Dr. Orban, but as the years went by, they noticed the two were getting closer together and whirling around each other faster and faster. “There was no good explanation,” he said, about why the two should be forming an ever-tightening orbit, except, he said, that “there’s such a large amount of mass in both those objects that as they orbit, they emit gravity waves and the gravity waves carry energy away from the system and that makes them shrink a little bit closer together.” However, it was through the LIGO interferometers’ actual detection of our own planet shrinking and stretching that confirms the speculation, said Orban.
Researchers now hope the knowledge gained from this week’s announcement confirming the existence of gravity waves will allow them to begin mapping the dark matter making up the lion’s share of the universe—and to peer ever farther back in time—perhaps even to the Big Bang itself.
Dr. Orban shared that he is currently trying to bring a course on black holes, Astronomy 1142, to Marion campus students. “It is an exciting time to be in this field,” said Dr. Orban, “and it’s that excitement I hope to bring to the students I teach at Ohio State Marion.”
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