Searching for biosignatures in the atmospheres of nearby exoplanets invariably opens up the prospect of folding in a search for technosignatures. Biosignatures seem much more likely given the prospect of detecting even the simplest forms of life elsewhere – no technological civilization needed – but ‘piggybacking’ a technosignature search makes sense. We already use this commensal method to do radio astronomy, where a primary task such as observation of a natural radio source produces a range of data that can be investigated for secondary purposes not related to the original search. So technosignature investigations can be inexpensive, which also means we can stretch our imaginations in figuring out what kind of signatures a prospective civilization might produce. The odds may be long but we do have one thing going for us. Whereas a potential biosignature will have to be screened against all the abiotic ways it could be produced (and this is going to be a long process), I suspect a...

The search for life on planets beyond our Solar System is too often depicted as a binary process. One day, so the thinking goes, we'll be able to directly image an Earth-mass exoplanet whose atmosphere we can then analyze for biosignatures. Then we'll know if there is life there or not. If only the situation were that simple! As Alex Tolley explains in his latest essay, we're far more likely to run into results that are so ambiguous that the question of life will take decades to resolve. Read on as Alex delves into the intricacies of life detection in the absence of instruments on a planetary surface. by Alex Tolley "People tend to believe that their perceptions are veridical representations of the world, but also commonly report perceiving what they want to see or hear." [17] Evolution has likely selected us to see dangerous things whether they are there or not. Survival favors avoiding a rustling bush that may hide a saber-toothed cat. We see what we are told to see, from gods in...

I’m delighted to see the high level of interest in Dysonian SETI shown not only by reader comments here but in the scientific community at large. I wouldn’t normally return to the topic this quickly but for the need to add a quick addendum to our discussions of Project Hephaistos, the effort (based at Uppsala University, Sweden) to do a deep dive into data from different observatories looking for evidence of Dyson spheres in the form of quirks in the infrared data suggesting strong waste heat. Swiftly after the latest Hephaistos paper comes a significant re-examination of the seven Dyson sphere candidates that made it through that project’s filters. You’ll recall that all seven were M-dwarfs, which struck me at the time as unusual. Only seven candidates emerged from over five million stars sampled, interesting especially because the possibility of a warm debris disk seemed to be ruled out. But Tongtian Ren (Jodrell Bank Centre for Astrophysics), working with Michael Garrett and...

I’m enjoying the conversation about Project Hephaistos engendered by the article on Dyson spheres. In particular, Al Jackson and Alex Tolley have been kicking around the notion of Dyson sphere alternatives, ways of preserving a civilization that are, in Alex’s words, less ‘grabby’ and more accepting of their resource limitations. Or as Al puts it: One would think that a civilization that can build a ‘Dyson Swarm’ for energy and natural resources would have a very advanced technology. Why then does that civilization not deploy an instrumentality more sly? Solving its energy needs in very subtle ways… As pointed out in the article, a number of Dyson sphere searches have been mounted, but we are only now coming around to serious candidates, and at that only seven out of a vast search field. Two of these are shown in the figure below. We’re a long way from knowing what these infrared signatures actually represent, but let’s dig into the Project Hephaistos work from its latest paper in...

For a project looking for the signature of an advanced extraterrestrial civilization, the name Hephaistos is an unusually apt choice. And indeed the leaders of Project Hephaistos, based at Uppsala University in Sweden, are quick to point out that the Greek god (known as Vulcan in Roman times) was a sort of preternatural blacksmith, thrown off Mt. Olympus for variously recounted transgressions and lame from the fall, a weapons maker and craftsman known for his artifice. Consider him the gods’ technologist. Who better to choose for a project that pushes SETI not just throughout the Milky Way but to myriads of galaxies beyond? Going deep and far is a sensible move considering that we have absolutely no information about how common life is beyond our own Earth, if it exists at all. If the number of extraterrestrial civilizations in any given galaxy is scant, then a survey looking for evidence of Hephaistos-style engineering writ large will comb through existing observational data from...