Dark matter is estimated to constitute 84% of the matter in the universe and 23% of the total energy density, with almost all the rest being dark energy. Dark matter cannot be seen directly with telescopes; evidently it neither emits nor absorbs light or other electromagnetic radiation at any significant level. Instead, its existence and properties are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe.
In the Cthulhu Mythos, it is natural to assume that dark matter has some relationship with the normally hidden creatures of “From Beyond”. As of 2013, there is a fringe theory in astrophysics that at least some of the universe's dark matter is tied up in structures called domain walls, each domain having its own value for a chaotic field left behind from the early universe.1 It is natural to assume that Lovecraft's “stars coming right” is in fact a reference to the motion of the Earth, indicated by the motion of the stars. Our planet will eventually enter a dark-matter domain where conditions are markedly different, and Cthulhu lives again.