The scientists who made a global splash in February by revealing that they had detected gravitational waves — invisible ripples in space-time that Einstein first predicted a century ago — kept something under their hat. They didn’t just do it once, they did it twice.

Even as they announced the detection of a wave that had traveled more than 1 billion light-years toward earth from the cataclysmic collision of two black holes, they were vetting a second signal from a similar collision in another distant corner of space.

Those two gravitational waves, rippling toward earth at the speed of light, registered at the twin detectors known as ­LIGO — massive finely tuned “listening devices’’ first conceived at MIT and located in remote Louisiana and Washington locales — 14 weeks apart.

And though the waves kept right on moving past the earth in less than the blink of an eye, unseen and undetectable except to LIGO, they carried messages for the researchers from two violent collisions, long ago and across the universe.

“It’s a wondrous thing,’’ said David Shoemaker, who leads the MIT lab that helped build the detectors, in an interview coinciding with the publication of the new findings Wednesday. “Three months apart, 1.4 billion years ago, these two events happened at two different places in the sky.’’

The finding does more than prove the first was no fluke. As the detectors become more sensitive, and as more like them are built, researchers expect to detect waves from many more black hole collisions and from other cataclysms, like the collision of neutron stars, the researchers said.

“With this, we can tell you now, the era of gravitational-wave astronomy has begun,’’ said Gabriela González, a Lousiana State University professor and the spokeswoman for the LIGO (which stands for Laser Interferometer Gravitational-Wave Observatory) scientific collaboration, during a press conference.

The twin detectors and the 1,000-scientist coalition, led by the California Institute of Technology and MIT and funded by the National Science Foundation, grew out of a classroom thought experiment first proposed by MIT physics professor Rainer Weiss half a century ago.

Decades in the making, the LIGO detectors had not quite reached their designed sensitivity when the first wave struck last Sept. 14. Though it squeezed and stretched their 2.5-mile arms by just 1/1,000th of a proton’s width, that signal was so clear and strong that it played as a chirp on control-room speakers and danced distinctively on the real-time graphs that had been fed until then by the constant wiggles of the mirrors based on rumbles here on earth.

As researchers were parsing that signal for a paper and preparing to announce “the chirp heard round the universe,’’ the next wave hit late on Christmas Day at the two observatories — officially, 3:38 a.m. on Dec. 26 in the international standard known as Coordinated Universal Time.

“Einstein’s Christmas present,’’ Rick Fienberg, a spokesman for the American Astronomical Society dubbed it on Wednesday, during the webcast press conference at the society’s 228th meeting.

This wave came from the final, dramatic collision of two black holes that had been circling each other — one more than 14.2 times as massive as our sun, the other 7.5 times — and that slammed together to form an even bigger, spinning black hole 20.8 times as massive as our sun, while releasing the remaining energy in the form of gravitational waves.

With a third observatory known as VIRGO slated to begin running soon in Italy, and with others planned for Japan and India, the researchers will be able to better “triangulate’’ the locations in the universe where incoming gravitational-waves originated.

Eric Moskowitz can be reached at eric.moskowitz@globe.com. Follow him on Twitter @GlobeMoskowitz.