‘Look on my works, ye Mighty, and despair!’ says Ozymandias’s ruined statue in the desert of Shelley’s imagination. Shelley’s sonnet is often interpreted as a sober warning that human works are fleeting, but when I read it as a young boy it kindled a sense of adventure; it suggested a wonderfully mysterious past beneath my familiar suburban surroundings.
We use the word ‘archaeology’ to describe this effort, because looking into deep home stars in a technological shell, or a swarm of spacecraft, in order to capture its energy. A sphere with the radius of Earth’s orbit would have an interior surface area 100 million times as large as the surface area of our planet. In 1966, Carl Sagan suggested that such spheres might be detectable, but he cautioned that they would be hard to distinguish from natural objects that gave off a similar infrared signature. Decades later, Carrigan would tell New Scientist that he wanted to try anyway, that he ‘wanted to get into the mode of the British Museum, to go and look for artefacts’.
True to his word, Carrigan has conducted a series of searches for Dyson spheres, following earlier work by the Russian astronomers Vyacheslav Ivanovich Slysh and MY Timofeev. Carrigan combed IRAS, the infrared sky survey that dates back to the 1980s, looking for the distinct infrared signatures calculated for this purely theoretical
The field’s deeper thinkers are starting to wonder if there might be other ways to search. Milan Ćirković, from the Astronomical Observatory of Belgrade, has suggested we go after large artificial objects in transiting orbits. He says we ought to look for something like the huge Astronomers are puzzled by them because globular clusters — ancient cities of stars that sit in a spherical halo around the 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.
n the context of interstellar archaeology, the problem is that we have no analogues in our experience for what advanced cultures might create. Interstellar archaeologists are tasked with sifting through gigabytes of data, not layers of soil, but the principle is the same. In a recent paper with Robert Bradbury and George Dvorsky, Milan Ćirković offered a paradigm for a new SETI, one that would include not only searches like these but a wide range of ‘future studies’ that would encompass how a post-biological intelligence might emerge and make itself known — intentionally or unintentionally.