“Ladies and gentlemen, we have detected gravitational waves.”
Northwestern Alumnus David Reitze ’83 won’t soon forget the proclamation he delivered to the world on February 11, 2016.
As the Laser Interferometer Gravitational-Wave Observatory (LIGO) executive director at the California Institute of Technology, Reitze stood before a large media contingent at the National Press Club in Washington, DC, as tens of thousands of people around the world watched online.
Ten months later, Reitze returned to Northwestern University to share his LIGO experience — and the painstaking science behind proving Einstein right.
One of the highlights of Reitze’s two-day visit was a December 1 colloquium, where he discussed gravitational waves and what makes them so difficult to detect and at the same time such powerful and unique probes of the universe.
By measuring the tiny disturbances gravitational waves make to space and time as they pass through the Earth, LIGO scientists were able to observe ripples in the fabric of spacetime from the collision of two black holes in the distant universe. Based on signals received at the LIGO observatories in Louisiana and Washington, physicists concluded that the gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive, spinning black hole.
The discovery confirmed a major prediction of Albert Einstein’s 1915 general theory of relativity.
The discovery was made possible by the enhanced capabilities of Advanced LIGO, an ongoing major upgrade to the observatories that is increasing the sensitivity of the instruments so that, for example, LIGO can now see binary black holes at an average distance of 2 billion light years.
Finding gravitational waves was “really a triumph of science and human ingenuity and tenacity,” says Reitze, a laser physicist who has been involved with LIGO since 1996. “It’s so cool that we can make devices that are capable of measuring these tiny, tiny effects that come from these massive cataclysmic collisions of black holes.
“Gravitational waves were something that Einstein predicted 100 years ago. It took 100 years for people to figure out a way to measure something that small. What we saw was unique. Nobody ever saw a pair of black holes colliding before.”
Read more about the discovery.