The Einstein Telescope

IEEE Spectrum reports:

According to Einstein's general theory of relativity, such events should create powerful waves of gravity—ripples in the curvature of space-time that alternately stretch and compress everything in their path.

Although scientists have been trying for decades, they have yet to directly observe these waves. ...

The instrument, which won't start making observations until 2025 at the earliest, isn't a telescope in the Galilean sense; it and its predecessors are laser interferometers that measure tiny distortions—much smaller than the diameter of a proton—in the length of tubes several kilometers long. The telescope design includes three detectors, each consisting of two 10-kilometer-long arms—more than twice the size of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), the largest second-generation gravitational interferometer.

Einstein himself once wrote a paper claiming to show that gravity waves did not exist. The referee showed that he was wrong, and Einstein wrote a nasty letter to the editor. Einstein then submitted the paper elsewhere, using the referee's work to correct his errors. Einstein did not acknowledge the referee, of course, and only submitted to journals that would publish his papers without refereeing.

LIGO and the Einstein telescope are very similar to the Michelson-Morley experiment, which tried to measure the motion of the Earth in 1887, and which inspired relativity theory. Like the 1887 experiment, LIGO has failed to find any motion. Michelson-Morley is the most famous failed experiment, while LIGO is the most expensive failed experiment. The Large Hadron Collider may ultimately be the most expensive failed experiment.

The chief difference between Michelson-Morley and LIGO is that Michelson-Morley was trying to measure the motion of the Earth, while LIGO was trying to detect motion in another galaxy. That's right, it is supposed to ignore everything on Earth, our Solar System, and in this galaxy. The biggest source of error is when a bus drives down a nearby street.