B Gravitational Wave Background: The Mysteries of the Universe

enorbet
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Pulsars as galaxy-wide "sensors" for net gravitational wave background
I don't know if this is the ideal sub-forum for this but I'd like to know more about this very recent activity I first saw here >>>>>'



It looks like this could be some actually testable, actual breakthrough advances in Physics and the evolution of our Universe. Any comments appreciated.
 
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Google finds http://nanograv.org/ with some background information.

It appears that that organization generates a dataset from the array of pulsars, and other authors attempt to analyze the data and interpret the result. I'm not familiar with the topic, but Google did find https://ui.adsabs.harvard.edu/abs/2020ApJ...900..102A/abstract as one such example, I don't have a complete set of such analsyis or have any idea of how well they analyses have been accepted.
 
I asked a question here, probably over 15 years ago on entanglement and I appreciated the thoughtful answers I received back then. The intervening years haven't made me any more knowledgeable in physics, so forgive my naïveté ! If a have a piece of paper in an area of high gravity, lets say near a black hole, and I draw a triangle on this paper and 'measure' the angles of the triangle, will they add to 180 degrees? How about if I'm looking at this paper outside of the (reasonable)...
From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...
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