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Would it be a major discovery even with 5-sigma, given that it confirms what everyone thought anyway, namely that there are quite a lot of tens-to-hundreds-of-nanohertz gravitational waves, enough to support the idea of a stochastic background? That is, "General Relativity's right about gravitation yet again". Interesting, because it's yet another way of confirming the theory (at the linear level and a flavour of the equivalence principle), but not at all startling. What's intriguing is that pulsar timing arrays ("PTA") like NANOGrav, CPTA, EPTA, InPTA, PPTA etc may be seeing more gravitational waves than expected. Assuming the sources are all SMBH binaries in ~month-long mutual orbits, then maybe there are more SMBHs than expected, or they binarize more commonly than expected or earlier in the universe than expected, or through some unexpectedly popular channel other than galaxy mergers. Pulsar timing arrays appear likely to produce increasingly useful data about galaxy formation, mergers, and evolution. I think that having both LIGO (Hz-kHz, so ~stellar mass) and PTAs (~nHz, and much larger mass) giving views into different parts of the spectrum in gravtiational wave astronomy is pretty major. That LIGO appeared to work at all was awfully cool; and now we have these large international PTA collabs appearing to work too. I am tempted to compare high-end early 20th century optical telescopes at the dawn of radio telescopes: same electromagnetic spectrum, but sensitivity to different wavelengths, with different wavelengths associated with different phenomena and different objects. PS: I like InPTA's set of cartoons at https://twitter.com/InPTA_GW/status/1674208503395934208 (thread). |