  Tidal effects have long ago locked the Moon in synchronous rotation with the
Earth and progressively increase the Earth-Moon distance. This "tidal
acceleration" hinges on dissipation. Binaries containing black holes may also
be tidally accelerated, dissipation being caused by the event horizon - a
flexible, viscous one-way membrane. In fact, this process is known for many
years under a different guise: superradiance. In General Relativity, tidal
acceleration is obscured by gravitational-wave emission. However, when coupling
to light scalar degrees of freedom is allowed, an induced dipole moment
produces a "polarization acceleration", which might be orders of magnitude
stronger than tidal quadrupolar effects. Consequences for optical and
gravitational-wave observations are intriguing and it is not impossible that
imprints of such mechanism have already been observed.
