Ligo.

Simultaneous signal

There is other evidence to suggest that at least one of the later detections came from a gravitational wave. On 17 August 2017, the orbiting Fermi telescope saw a burst of electromagnetic radiation at the same time as the LIGO and Virgo detectors picked up a signal. Analysis of all the evidence suggests that both signals came from the brutal collision of two neutron stars.

The double whammy makes LIGO’s detection seem unequivocal. Even here, though, the Danish group is dissenting. They point out that the collaboration initially registered the event as a false alarm because it coincided with what’s known as a “glitch”. The detectors are plagued by these short, inexplicable bursts of noise, sometimes several every hour. They seem to be something to do with the hardware with which the interferometers are built, the suspension wires and seismic isolation devices. Cornish says that LIGO analysts eventually succeeded in removing the glitch and revealing the signal, but Jackson and his collaborators are again unconvinced by the methods used, and the fact there is no way to check them.