A year ago Tuesday, scientists inside two giant L-shaped instruments saw a strange blip on their screens they could hardly believe.
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.
"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.
One killer application is to reveal supernovas — huge, exploding stars that seed the universe with elements like carbon, nitrogen, and oxygen — hours before they're visible to telescopes.
"Gravitational waves arrive at Earth long before any light does," Bartos said. The reason is that the star gets in the way of itself.
"All of this stuff tries to come out, including light, but it bumps into the star's matter and gets stuck until the whole star collapses. But gravitational waves can pass right through."
But it's not just about pointing our telescopes at supernovas before we can see them explode. (Not to suggest this isn't insanely cool)
Gravitational waves will reveal the hidden, seething cores of supernovas. "Right now the only tools to explore what happens inside are computer models," Bartos said.
There is another wild application of gravitational waves: Hearing the birth of black holes.
This happens deep inside supernovas, or when two ultra-dense dead stars, called neutron stars, merge together.
Dana Berry, SkyWorks Digital, Inc.
Such an event should cause gravitational waves to spill outward in all directions at the speed of light.
Physicists also have no idea if black holes have any structure. But gravitational waves can emanate from the surface — a point of no return called the event horizon.
"The closest you can get to black hole is gravitational waves," Bartos said. "There should be no structure to the surface, but if there is, if black holes have any 'hair,' we could detect that."
Gravitational waves will also help us take inventory of the weirdest, wildest objects in the universe that we couldn't previously detect.
That includes binary black hole systems — just like the one that triggered the first gravitational waves humanity ever recorded using LIGO.
In that case, two black holes merged together and instantly zapped three suns' worth of matter into pure gravitational wave energy.
We have no idea how many more binary black holes systems are lurking out there, caught in a cosmic dance of death.
We also don't know how many neutron stars are out there in pairs or in orbit with a black hole. Gravitational waves will tell us when those objects collide, and how frequent they are.
And then there's dark matter, which makes up about 80% of all matter in the universe— but no one has directly detected. It outweighs all the stars and planets by four-to-one.
One scientist at NASA thinks gravitational waves could reveal that all of this missing mass is actually just a whole heck of a lot of black holes, which formed at the dawn of the cosmos yet have evaded detection.
Bartos says "it's highly unlikely this theory is correct, but we can't rule it out." He's instead betting on sensitive experiments that are looking for tiny "weakly interactive massive particles," or WIMPs.
Gravitational waves may also reveal things out there, deep in the universe, that scientists have not yet dreamed up.
"We can be rather sure that we’ll see big surprises," says Kip Thorne, a Caltech physicist and cofounder of LIGO. "My hope is for the biggest surprise we've ever seen."
Sarah Kramer contributed to this post.
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