Fast Radio Bursts from Extragalactic Light Sails
  We examine the possibility that Fast Radio Bursts (FRBs) originate from the
activity of extragalactic civilizations. Our analysis shows that beams used for
powering large light sails could yield parameters that are consistent with
FRBs. The characteristic diameter of the beam emitter is estimated through a
combination of energetic and engineering constraints, and both approaches
intriguingly yield a similar result which is on the scale of a large rocky
planet. Moreover, the optimal frequency for powering the light sail is shown to
be similar to the detected FRB frequencies. These `coincidences' lend some
credence to the possibility that FRBs might be artificial in origin. Other
relevant quantities, such as the characteristic mass of the light sail, and the
angular velocity of the beam, are also derived. By using the FRB occurrence
rate, we infer upper bounds on the rate of FRBs from extragalactic
civilizations in a typical galaxy. The possibility of detecting fainter signals
is briefly discussed, and the wait time for an exceptionally bright FRB event
in the Milky Way is estimated.
