 black hole merger was made at 09:50:45 GMT on 14 September.
The laser interferometers operated by LIGO had only just come online after several years refurbishment to enhance their sensitivity. They weren't even in a formal science observation mode. The researchers were still going through commissioning checks when the detectors picked up the signal - a disturbance equivalent to someone nudging the ultra-quiet equipment by minute fractions of the width of a proton, the particle at the heart of all atoms.
The LIGO lab at Livingston in Louisiana saw it first. The Hanford, Washington State, observatory 3,000km away sensed the bump seven milliseconds later. The distance to the event, the scientists are pretty confident about; the location, less so. Somewhere in the southern sky.
In some ways, it's difficult to know what to concentrate on. Is it the history-making detection of the waves themselves, or the detail of astrophysics they represent? This is the first direct observation of black holes, of black holes this size, and of them orbiting each other and merging.
And all the numbers are exquisitely in agreement with Einstein's equations. As predicted, the waves radiate at the speed of light - meaning the graviton, the putative particle that mediates gravitation, is massless (to the level that it's possible to tell).
"Although Einstein's equations are famously complicated, they are the simplest equations he could have come up with, given all the constraints he had to satisfy," commented Bernie Schutz from Cardiff University.
"It is remarkable that nature didn't add in even more complexity. But the equations are what they are, and they're beautiful."
There will of course need to be further detections. The scientists think they may also have seen an event, much smaller, some weeks later, but this will need further assessment.
Looking to the summer, the LIGO labs will be running again after a period of downtime. When this happens, they'll be joined by a third observatory called Virgo, built near Pisa in Italy. Others are coming, too, in Japan and in India.
With all these "ears on the cosmos", it should be easier to identify where precisely in the sky the detected events are occurring.
And the European Space Agency is developing a gravitational wave observatory to put in orbit far from Earth. It will launch in the 2030s.
Currently, it's not the grand mission that everybody had hoped for, because the US space agency got in a muddle over its funding some years back and dropped the project. The scale of the mission was therefore redrawn. Many now hope that this historic breakthrough will prompt Nasa to come back in.
"The compromise that was made, to build it in Europe so that the Americans didn't have to contribute, because they weren't going to, was not the best thing to do for the science; not for the size and the risk of doing that space mission," observed MIT's Rai Weiss.
"Consequently, many of us are trying to get the collaboration re-established."
It is really only by going into space and measuring gravitational waves from even bigger events, away from the noisy surface of the Earth, that researchers expect to see small chinks start to emerge in those glorious equations of Einstein.
Who gets the prize?
It is inevitable on these occasions that talk turns to Nobel Prizes. No-one is in any doubt that Thursday's announcement deserves one; the debate, as ever, is over who should receive it. Obvious candidates include the American Kip Thorne, the Scotsman Ron Drever and the German-born Rai Weiss himself. They are regarded as the fathers of LIGO, having proposed the concept back in the 1980s.
But for Jim Hough, who started working on gravitational waves as a postgrad in the late 1970s, it would be appropriate if some of the glory went to the broad collaboration of researchers who made LIGO what it is. One thousand and four authors are listed on the breakthrough paper in Physical Review Letters.
"The Nobel committee should have given a prize to the Large Hadron Collider itself for the detection of the Higgs boson. All those experimen