  Milne was having none of it. In the next month’s Observatory—the informal monthly publication of the Royal Astronomical Society—he took Eddington and his theoretical-realist colleagues to task, concluding that “theories differ simply and solely when their predictions as to phenomena differ”; most importantly, “this method of comparison avoids all reference to distance-assignments, world-geometry, schemes of projection or the like” (Milne 1934b). In other words, metaphysics was to be avoided in cosmology; space, spacetime, geometry and the like were to be rejected as scientific realities, replaced by reference simply and solely to observations. The only realities, according to Milne, were what could be reported among observers about light signals and clocks.