One thing I don't quite understand - how can the "chirp" from LIGO be unambiguously categorized as extraterrestrial in origin? The waveform shown onscreen in the NYtimes video looks like an extremely noisy signal - not sure if that's the actual sampled data or just an artistic rendition. Couldn't there be a variety of physical disturbances that explain a sine-tone sweep like that, given how sensitive the instrument is to physical vibrations?
There are two independent sites, 2000 miles apart. Additionally, each site has two perpendicular experiments: one shows contraction when the perpendicular one shows expansion. Orientations at both sites are aligned I presume.
