Changes

=== The event of September 14, 2015 ===

=== The event of September 14, 2015 ===

This event was observed shortly after turning on the enhanced version of the LIGO detection system, and reported in January 2016.<ref>http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102]</ref>  Making sure that it wasn't a detection of random noise required comparing the waveforms with the predicted waveforms from theoretical calculations of the final approach and "ringdown" of a merger of two black holes.  The signal closely matched theoretical predictions.<ref>https://www.ligo.caltech.edu/image/ligo20160211a</ref>

This event was observed shortly after turning on the enhanced version of the LIGO detection system, and reported in January 2016.<ref>http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102]</ref> It was the merger of two black holes, each about 30 times the mass of the Sun, about 1.3 billion light years away and hence 1.3 billion years ago. Making sure that it wasn't a detection of random noise required comparing the waveforms with the predicted waveforms from theoretical calculations of the final approach and "ringdown" of a merger of two black holes.  The signal closely matched theoretical predictions.<ref>https://www.ligo.caltech.edu/image/ligo20160211a</ref>

The match showed a confidence of better than "five sigma", that is, a probability of less than one in a million that this was a coincidence.  The same event was detected at both observatories, a small fraction of a second apart, as the wave passed through the Earth.

The match showed a confidence of better than "five sigma", that is, a probability of less than one in a million that this was a coincidence.  The same event was detected at both observatories, a small fraction of a second apart, as the wave passed through the Earth.