Alien civilisations that have terraformed multiple planets may be detectable from afar
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Nearby planets that look unusually alike could be a sign of spacefaring alien life that has travelled between stars, researchers have suggested.
Astronomers searching for extraterrestrial life tend to look for specific signals, either in the form of “biosignatures” – molecules that are only produced by biological processes – or “technosignatures”, abnormal patterns of light that may have been produced by technologies.
Both of these rely on assumptions…