  We consider the possibility that gravity breaks parity, with left and right
handed gravitons coupling to matter with a different Newton's constant and show
that this would affect their zero-point vacuum fluctuations during inflation.
Should there be a cosmic background of gravity waves, the effect would
translate into anomalous CMB polarization. Non-vanishing TB (and EB)
polarization components emerge, revealing interesting experimental targets.
Indeed if reasonable chirality is present a TB measurement would provide the
easiest way to detect a gravitational wave background. We speculate on the
theoretical implications of such an observation.
