By Bill Christensen
Should we be looking for extraterrestrial civilizations, rather than just listening for them, as we do in the SETI (Search for Extraterrestrial Intelligence) project? That is the suggestion of a French astronomer, Luc Arnold, in his paper Transit Lightcurve Signatures of Artificial Objects. He believes that the transit of large artificial objects in front of a sun could be a used for the emission of attention-getting signals.
In his paper, he describes the expected lightcurve signatures expected from passing objects of various shapes across a sun. The challenge is to use a shape that provides an unambiguous signature.
In his 1970 classic Ringworld, science fiction author Larry Niven describes the discovery of an enormous artifact; a ring of material that completely surrounds a star, providing a staggering amount of living space. The alien species that discovered the star asks humans for their opinion on what they have found:
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