The dimensionless age of the Universe: a riddle for our time
  We present the interesting coincidence of cosmology and astrophysics that
points toward a dimensionless age of the universe H_0*t_0 that is close to one.
Despite cosmic deceleration for 9 Gyr and acceleration since then, we find
H_0t*_0 = 0.96 +/- 0.01 for the LCDM 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_0*t ~ 1.0 +/- 0.1$. The wide range of
possible values for H_0*t_0 realized during comic 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 Omega_Matter and Omega_Lambda for which the usual coincidence
problem holds but for which H_0*t_0 is not close to 1.
