  From the general assumption that gravity originates from the coupling and
thermal equilibrium between matter and vacuum, after a derivation of Newton's
law of gravitation and an interpretation of the attractive gravity force
between two classical objects, we consider the macroscopic quantum gravity
effect for particles whose wave packets are delocalized at macroscopic scale.
We predict an abnormal repulsive gravity effect in this work. For a sphere full
of superfluid helium, it is shown that with a gravimeter placed in this sphere,
the sensitivities of the gravity acceleration $\Delta g/g$ below $10^{-8}$
could be used to test the abnormal quantum gravity effect, which satisfies the
present experimental technique of atom interferometer, free-fall absolute
gravimeters and superconducting gravimeters. We further propose a
self-consistent field equation including the quantum effect of gravity. As an
application of this field equation, we give a simple interpretation of the
accelerating universe due to dark energy. Based on the idea that the dark
energy originates from the quantum gravity effect of vacuum excitations due to
the coupling between matter and vacuum, without any fitting parameter, the
ratio between dark energy density and matter density (including dark matter) is
calculated as 2.2, which agrees quantitatively with the result 7/3 obtained
from various astronomical observations.
