

3 Low-Energy Quantum
Gravity
According to the approach just described, non-renormalizable
theories are not fundamentally different from renormalizable ones.
They simply differ in their sensitivity to more microscopic scales
which have been integrated out. It is instructive to see what this
implies for the non-renormalizable theories which sometimes are
required to successfully describe experiments. This is particularly
true for the most famous such case, Einstein’s theory of gravity.
(See [58] for
another pedagogical review of gravity as an effective theory.)

