Forget that controversial History Channel show: the ruins of ancient alien civilisations may well exist beyond our atmosphere, and scientists are keen to go and search for them. The field of xenoarchaeology – the search for the material remains of extraterrestrial cultures – was once mainly a science fictional concept, but in recent times there has been much progress in nailing it down firmly to the realm of science present. Over at Aeon Magazine, Paul Gilster (of the Centauri Dreams blog) has posted a wonderful essay documenting some of the efforts being made to search for such ‘relics’, from Dyson spheres through to asteroid mining ventures. He also touches on the philosophical side of the search, noting the difficulty in predicting what these relics might be, when we are searching for something that is, quite literally, alien to us:

All of these searches ask us to put ourselves in the minds of beings about whom we know absolutely nothing. The physicist David Deutsch has flagged this as a problem for prediction of all kinds, not just those involving SETI. According to Deutsch, we can distinguish between ‘prophecy’ and ‘prediction’, with prophecy being the discussion of things that are not knowable, while prediction deals with conclusions that are based on good explanations of the universe. As prognosticators from Thomas Malthus to the Club of Rome have demonstrated, we may be able to identify problematic trends in the present that can be extended into the future, but we cannot know what knowledge we will acquire in the future to manage those problems. This is why no scientific era has succeeded in imagining its successor. The scientists of the late 19th century discovered this firsthand, when confronted with the emergence of quantum theory and relativity early in the early 20th. Both theories raised questions earlier theorists couldn’t have even formulated. In the context of interstellar archaeology, the problem is that we have no analogues in our experience for what advanced cultures might create. Patience is the byword as the effort proceeds, the same patience that Heinrich Schliemann’s successors have used to master the art of sifting through rubble, with careful digging and delicate brushwork sweeping aside soil to uncover the shape of a fragmentary artifact. Interstellar archaeologists are tasked with sifting through gigabytes of data, not layers of soil, but the principle is the same.

Where do you think the best place to look for alien ruins might be? Earth, our Solar System, or distant suns and galaxies? And what should we be looking for? A fascinating topic.

Link: Distant Ruins: Scientists used to scan the skies for messages from alien civilisations. Now they go looking for their ruins