  One of the major issues confronting theoretical physics is finding a quantum
theory of gravity and a resolution to the cosmological constant problem. It is
believed that a true quantum theory of gravity will lead to a solution to the
this problem. Finding a quantum theory of gravity has been a difficult issue
mainly because of the high energy scale required for testing quantum gravity
which is far the reach of current accelerators. Also general relativity does
not possess a natural time variable thus the nature of time is not clear in
quantum gravity, a problem called the time paradox. The two main approaches are
string theory and loop quantum gravity. String theory unifies all interaction
but provides a perturbative background dependent formulation which violates
general covariance. Loop quantum gravity provides a non-perturbative approach
but does not provide a unified theory of interactions, which most physicist
believe should be the case at Planck scale energies. It doesn't also seem to
connect with low energy phenomena.
  In this note I look at how quantum cosmology provides useful inference toward
a quantum gravity theory by merging inputs from the perturbative and the
non-perturbative approaches, and resolving the time paradox issue.
