radio source counts

In cosmology, radio source counts (or just source counts) is a method of detecting the curvature of space. In a flat, Euclidean space, a uniform distribution of radio sources (the scale of interest being cosmological distances, i.e., radio galaxies), with the same distribution of luminosities throughout, implies a certain pattern to the count of detectable sources at each luminosity:

log N = -1.5 log S

• S - a given flux density.
• N - number of sources at least as bright as S.

Divergence from this yields information about the geometry of the universe over time.