  In the exact (non-linear) formulation of general relativity (GR) no motion of
bodies can give origin to gravitational waves (GW's) - as it has been proved.
Accordingly, the measured rate of change of the orbital period of binary pulsar
B PSR1913+16 must have other causes, different from the emission of GW's; maybe
the viscous losses of the unseen pulsar companion, if it were e.g. a helium
star.
