Inhomogeneous Cosmology Redux
  An alternative to the postulate of dark energy required to explain the
accelerated expansion of the universe is to adopt an inhomogeneous cosmological
model to explain the supernovae data without dark energy. We adopt a void
cosmology model, based on the inhomogeneous Lema\^{i}tre-Tolman-Bondi solution
of Einstein's field equations. The model can resolve observational anomalies in
the $\Lambda CDM$ model, such as the discrepancy between the locally measured
value of the Hubble constant, $H_0=73.24\pm 1.74\,{\rm km}\,{\rm s}^{-1}\,{\rm
Mpc}^{-1}$, and the $H_0=66.93\pm 0.62\,{\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$
determined by the Planck satellite data and the $\Lambda CDM$ model, and the
lithium $^{7}{\rm Li}$ problem, which is a $5\sigma$ mismatch between the
theoretical prediction for the $^{7}{\rm Li}$ from big bang nucleosynthesis and
the value that we observe locally today at $z=0$. The void model can also
resolve the tension between the number of massive clusters derived from the
Sunyaev-Zel'dovich effect by the Planck satellite and the number expected from
the CMB anisotropies, and the CMB weak lensing anomaly observed in the Planck
data. The cosmological Copernican principle and the time and position today
coincidence conundrums in the $\Lambda CDM$ and void cosmological models are
discussed.
