On artificial transits feasibility and SETI
  It is known that the shape of a planet (oblateness, rings, etc.) slightly modifies the shape of the transit light curve. The forthcoming space missions (Corot, Kepler), able to detect the transit of Earth-like planets, could a fortiori also detect the transit of artificial planet-size objects if their shape is significantly different from a natural (planetary) object. Multiple artificial objects would also produce transit light curves easily recognizable from natural transits. Artificial transits, especially of multiple objects, could be used for the transmission of clear attention-getting signals, with a sky coverage (efficiency) comparable to that of the laser pulse method. Although out of reach of current human technologies, the building of an Earth-size 1-micron thick mask would require energy and bulk material amounts already managed on Earth today. The migration of the mask toward an inner orbit and its protection against asteroids or meteoroids are also briefly discussed. 
Luc Arnold (Observatoire de Haute-Provence CNRS   Saint-Michel-l'Observatoire France)