|The near simultaneous signal detection at both LIGO installations almost certainly precludes the possibility of an artifact.|
On September 14, 2015, the two LIGO (Laser Interferometer Gravitational-Wave Observatory)* installations — one at Hanford Washington, the other at Livingston, Louisiana. recorded near simultaneous signals attributed to gravity waves generated by the merger of two black holes with masses estimated to be 29 and 36 times that of the sun.
The event, which occurred at a distance of 1.3 billion light years, i.e., 1.3 billion years ago, is estimated to have converted mass equivalent to three times that of the sun to gravitational wave energy within less than a second, resulting in a peak power output many times that of all other energy sources in the visible universe.
The signal received at Livingston, arrived 7 milliseconds before the signal received at Hanford, indicating that the source was located in the southern Hemisphere.
All reports attribute the observations reported by LIGO to ripples in the fabric of space-time caused by the rotation and merger of black holes. Implicit to this interpretation is the notion that space is not empty but filled with a medium, or ether, in which gravity waves propagate.
This seems remarkably in view of the rejection by the physics community of Newton's luminiferous ether following the Michelson Morley experiment conducted in 1887, which demonstrated that the velocity of light was independent of its direction of travel from a source in motion relative to the ether. If light waves can traverse the vacuum without a medium to wave in, why not gravity waves too?
That argument, notwithstanding, Einstein held the existence of a medium in space in which gravity waves propagate to be necessary, a medium or ether now generally identified with the spacetime continuum implicit in Einstein's general theory of relativity. But not everyone agrees, and here. These ideas may seem slightly wacky, but they make me feel slightly better about proposing that space really is space, i.e., the absence of anything, and that any properties attributed to space are due to whatever happens to have been added thereto, dark energy, for example, or virtual particles. Not that I'd bet more than about 50 cents against Einstein. But then even Einstein had moments of doubt, remarking at one point:
Perhaps, ... we must also give up, by principle, the space-time continuum. It is not unimaginable that human ingenuity will some day find methods which will make it possible to proceed along such a path."———
* The LIGO detectors measure the distance between mirrors located in an evacuated tube at a distance of 4 km from one another. They are able to detect variation in distance between the mirrors equal to less than one ten thousandth the diameter of a proton, which is why the project has cost hundreds of millions of dollars!
Quanta Magazine: From Einstein’s Theory to Gravity’s Chirp
Physical Review Letter:
B.P. Abbot, et al. 2016: Observation of Gravitational Waves from a Binary Black Hole Merger
Gravitational Waves Detected 100 Years After Einstein's Prediction