  We re-examine the gravitational wave background resulting from inflation and
its effect on the cosmic microwave background radiation. The new COBE
measurement of a cosmic background quadrupole anisotropy places an upper limit
on the vacuum energy during inflation of $\approx 5 \times 10^{16}$ GeV. A
stochastic background of gravitational waves from inflation could produce the
entire observed signal (consistent with the observed dipole anisotropy and a
flat spectrum) if the vacuum energy during inflation was as small as $1.5
\times 10^{16}$ GeV at the 95\% confidence level. This coincides nicely with
the mass scale for Grand Unification inferred from precision measurements of
the electroweak and strong coupling constants, for the SUSY Grand Unified
Theories. Thus COBE could be providing the first direct evidence, via
gravitational waves, for GUTs, and supersymmetry. Further tests of this
possibility are examined, based on analyzing the energy density associated with
gravitational waves from inflation.
