“Up till now, we’ve been deaf to gravitational waves,” said David Reitze. “But today, we are able to hear them.”
It was one of many inspiring quotes from the news conference announcing the historic first direct detection of gravitational waves, the spacetime tremors forecast by Albert Einstein 100 years ago. Andrew Grant reported the announcement, which described the cosmic shake-up of two black holes merging and, in the process, releasing a burst of energy in the form of gravitational waves. The waves began their journey about 1.3 billion years ago (give or take half a billion), unaware that we would be listening. Very, very carefully.
The listening device, twin observatories known as LIGO, had just been boosted to a new level of sensitivity, now able to notice such black hole collisions up to 5 billion light-years away. LIGO’s interferometers can detect resulting spacetime ripples that kick laser waves out of alignment by less than the width of a proton — a tiny, next-to-nothing difference that can tell scientists if they have found their quarry.
Science writer Marcia Bartusiak, the author of an award-winning book about the gravitational wave quest, provides historical context to the new finding. She tells why building LIGO was such a big risk for the National Science Foundation, making the detection a big win for the agency.
Physicists weren’t actually surprised by the result. Many, like Kip Thorne, had invested decades of work on what they believed to be a sure thing. Einstein’s theory had passed all previous tests, after all. And in 1993, Russell Hulse and Joseph Taylor Jr. won a Nobel Prize for finding indirect evidence of the waves in the orbital motion of a pulsar and its companion.
Surprise or not, the news is truly exciting for science. For one thing, LIGO was able to perform just as Thorne, Rainer Weiss of MIT and others had argued. Even more thrilling, scientists now will be able to use gravitational waves to study the universe, detecting previously invisible events (like two black holes colliding). And, tantalizingly, by listening to the cosmos through this new channel, Reitze said, “we will also hear things that we never expected.”