LIGO/Caltech
It was the first evidence of gravitational waves - ripples in the fabric of space that careen across the universe, right through everything and everyone.
Einstein first predicted their existence 100 years ago, yet the famous scientist doubted we'd ever find any.
However, scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) experiment finally detected these cosmic reverberations on Sept. 14, 2015, thanks to the fearsome collision of two black holes about 1.3 billion light-years from Earth. They announced the discovery on Feb. 11, 2016, after months of exhaustive verification.
Then, in June 2016, the 900-scientist LIGO team announced their second detection, made on Dec. 2016, 2015.
"It confirms - it super-confirms - that these events are not flukes," astrophysicist Vicky Kalogera, who has been working with LIGO to analyze the signals, previously told Business Insider. "They're happening in nature and we can detect them every few months."
After an upgraded "Advanced" LIGO boots up this fall, Kalogera and others think the experiment could detect 10 or more new gravitational waves over the next year - and possibly up to 100 a year later on, with the help of another experiment called Advanced Virgo.
Business Insider previously spoke with Imre Bartos, also a physicist working with LIGO, and other researchers earlier this year about the "revolutionary" new era of astronomy they say has begun.
Here are just a handful of formerly impossible things astronomers could do with gravitational waves.