2016ApJ...828...35A

We present the interesting coincidence of cosmology and astrophysics that points toward a dimensionless age of the Universe H_0t0 that is close to one. Despite cosmic deceleration for 9 Gyr and acceleration since then, we find H_0t0=0.96±0.01 for the ΛCDM model that fits SN Ia data from Pan-STARRS, CMB power spectra, and baryon acoustic oscillations. Similarly, astrophysical measures of stellar ages and the Hubble constant derived from redshifts and distances point to H_0t ∼ 1.0±0.1. The wide range of possible values for H_0t0 realized during cosmic evolution means that we live at what appears to be a special time. This "synchronicity problem" is not precisely the same as the usual coincidence problem, because there are combinations of Ω_M and Ω_Λ for which the usual coincidence problem holds but for which H_0t0 is not close to 1.