  A quantum measurement-like event can produce any of a number of
macroscopically distinct results, with corresponding macroscopically distinct
gravitational fields, from the same initial state. Hence the probabilistically
evolving large-scale structure of space-time is not precisely or even always
approximately described by the deterministic Einstein equations. Since the
standard treatment of gravitational wave propagation assumes the validity of
the Einstein equations, it is questionable whether we should expect all its
predictions to be empirically verified. In particular, one might expect the
stochasticity of amplified quantum indeterminacy to cause coherent
gravitational wave signals to decay faster than standard predictions suggest.
This need not imply that the radiated energy flux from gravitational wave
sources differs from standard theoretical predictions. An underappreciated
bonus of gravitational wave astronomy is that either detecting or failing to
detect predicted gravitational wave signals would constrain the form of the
semi-classical theory of gravity that we presently lack.
