Why is Universe so dark ?
  In this presentation prepared for a general audience, we briefly mention the
shortcomings of standard model of universe. We then focus on the late time
inconsistency of the model dubbed age crisis whose resolution requires the
presence of a repulsive effect that could be sourced either by dark energy or
by a large scale modification of gravity. By and large, our description is
based upon Newtonian cosmology which is simple and elegant despite of its
limitations. On heuristic grounds, we explain how a tiny mass of graviton could
account for late time cosmic acceleration. We also include a brief discussion
on the underlying physics of Type Ia supernovae explosion and the direct
confirmation of late time acceleration of Universe by the related observations.
