  It is very likely that the quantum description of spacetime is quite
different from what we perceive at large scales, $l\gg (G\hbar/c^3)^{1/2}$. The
long wave length description of spacetime, based on Einstein's equations, is
similar to the description of a continuum solid made of a large number of
microscopic degrees of freedom. This paradigm provides a novel interpretation
of coordinate transformations as deformations of "spacetime solid" and allows
one to obtain Einstein's equations as a consistency condition in the long
wavelength limit. The entropy contributed by the microscopic degrees of freedom
reduces to a pure surface contribution when Einstein's equations are satisfied.
The horizons arises as "defects" in the "spacetime solid" (in the sense of well
defined singular points) and contributes an entropy which is one quarter of the
horizon area. Finally, the response of the microstructure to vacuum energy
leads to a near cancellation of the cosmological constant, leaving behind a
tiny fluctuation which matches with the observed value.
