The cosmic coincidence as a temporal selection effect produced by the age distribution of terrestrial planets in the universe

The energy densities of matter and the vacuum are currently observed to be of the same order of magnitude: (Ω_m0 ≈ 0.3) ∼ (Ω_Λ0 ap; 0.7). The cosmological window of time during which this occurs is relatively narrow. Thus, we are presented with the cosmological coincidence problem: why, just now, do these energy densities happen to be of the same order? Here we show that this apparent coincidence can be explained as a temporal selection effect produced by the age distribution of terrestrial planets in the universe. We find a large (∼68%) probability that observations made from terrestrial planets will result in finding Ω_m at least as close to Ω_Λ as we observe today. Hence, we, and any observers in the universe who have evolved on terrestrial planets, should not be surprised to find Ω_m0 ∼ Ω_Λ0.This result is relatively robust if the time it takes an observer to evolve on a terrestrial planet is less than ∼10 Gyr.