Avi Loeb and Freeman Dyson on the future of the universe

This morning I was delighted to receive an email from Avi Loeb, who’s paper on the (far) future of astronomy we discussed yesterday. Avi shared with me a conversation he had by email with another noted theorist, Freeman Dyson. The premise of Avi’s paper is that about a trillion years from now, all extragalactic light sources will cease to be visible due to the accelerating expansion of the universe. Future astronomers would therefore be stuck looking only within their own galaxy. Not only would the absence of extragalactic sources make for a (apparently) lonely universe, but it would deprive future astronomers of the tools that we have used to arrive at our current understanding of cosmology, such as extragalactic supernovae and the cosmic microwave background (CMB) radiation. Despite this, Avi suggests an observational signature by which these astronomers could still derive the standard cosmological model: hypervelocity stars.In their correspondence, Freeman, in his role as an “incurable optimist,” suggests a means by which future civilizations could avoid this fate. He proposes that a civilization could harness the gravitational energy of a group of galaxies in some way as to pull together colossal collections of galaxies before they were thrown apart from each other by cosmological expansion. Perhaps this will remind you of another one of his well-known ideas for civilization-scale engineering, the Dyson Sphere. Freeman suggests searching for such anomalous overdensities of galaxies to detect such “cosmic engineering.”Avi notes two possible observational signatures of such engineering: redshift surveys and the Sachs-Wolfe effect. Redshift surveys such as SDSS make 3D maps of the large scale structure of the local universe by...