If we're
going to find an extraterrestrial intelligence (ETI), we're going to
recognize their signatures. These signs can be organized into three
basic types: spectral signatures, physical artifacts and structures, and
remnants, or byproducts, of their technological activities. Some of
these signatures could be deliberate attempts to get our attention,
while others are simply leakage.
Should
we detect these signatures, however, the challenge will in determining
which are the work of an ETI and which are the products of some unknown
or bizarre natural phenomena (like the time we thought quasars were an
alien beacon).
