Hugh Pickens writes writes: "Charles Q. Choi writes that hairspray could one day serve as the sign that aliens have reshaped distant worlds because one group of gases that might be key to terraforming planets are chlorofluorocarbons (CFCs), long-lived non-toxic greenhouse gases that were often used in hairspray and air conditioners, among many other products. "Our hypothesis is that evidence of intelligent life might be evident in a planetary atmosphere," says astrobiologist Mark Claire at the Blue Marble Space Institute of Science. CFCs are entirely artificial, with no known natural process capable of creating them in atmospheres. Detecting signs of these gases on far-off worlds with telescopes might serve as potent evidence that intelligent alien civilizations were the cause, either intentionally as part of terraforming or accidentally via industrial pollution. "An industrialized civilization will be one that will use its planetary resources for fabrication, the soon-to-be-detectable-from-Earth atmospheric byproducts of which could be a tell-tale sign of their activity," says astrobiologist Sanjoy Som. CFCs can be easily recognized in planetary atmospheres because their atmospheric “fingerprint” (i.e. chemical spectra) is very different from natural elements, and are a tell-tale sign that life on the surface has advanced industrial capabilities. Using state-of-the-art computer models of atmospheric chemistry and climate, researchers plan to discover what visible signs CFCs and other artificial byproducts of alien terraforming or industry might have on exoplanet atmospheres. "We are about a decade away of being able to measure detailed compositions of the atmospheres of extrasolar planets," says Som."
Hugh Pickens writes writes: "Ross Anderson writes that Freeman Dyson predicted in 1960 that every civilization in the Universe eventually runs out of energy on its home planet, a major hurdle in a civilization's evolution, and that all those who leap over it do so in precisely the same way: they build a massive collector of starlight, a shell of solar panels to surround their home star. Last month astronomers began a two-year search for Dyson Spheres, a search that will span the Milky Way, along with millions of other galaxies funded by a sizable grant from the Templeton Foundation, a philanthropic organization that funds research on the "big questions" that face humanity, questions relating to "human purpose and ultimate reality." Compared with SETI, a search for Dyson Spheres assumes that the larger the civilization, the more energy it uses and the more heat it reradiates so if Dyson Spheres exist, they promise to give off a very particular kind of heat signature, a signature that we should be able to see through our infrared telescopes. "A Dyson Sphere would appear very bright in the mid-infrared," says project leader Jason Wright. "Just like your body, which is invisible in the dark, but shines brightly in mid-infrared goggles." A civilization that built a Dyson Sphere would have to go to great lengths to avoid detection by building massive radiators that give off heat so cool that it would be undetectable, a solution that would involve building a sphere that was a hundred times larger than necessary. "If a civilization wants to hide, it's certainly possible to hide," says Wright, "but it requires massive amounts of deliberate engineering across an entire civilization.""