Dyson Spheres, those theorized mega-construction projects of advanced extraterrestrials, may be somewhere in space waiting to be discovered, but so far the search for them has come up empty. Two researchers funded by the Templeton Foundation's New Frontiers in Astronomy and Cosmology program, Jason Wright of Pennsylvania State University and Matt Povich of the California State Polytechnic, are the latest to search and find nothing.
Originally proposed by the physicist Freeman Dyson in 1960, Dyson Spheres are thought to be huge structures in space built by advanced civilizations to trap and use the energy of a whole star, or perhaps even a whole galaxy. The idea caught on with science fiction writers, and even figured in an episode of Star Trek: The Next Generation. But searches by Vyacheslav Slysh at the Space Research Institute in Moscow in 1985 and by Richard Carrigan at Fermilab in 2009, who used data from the Infrared Astronomical Satellite, produced no results.
Originally people conceived of a Dyson Sphere as an actual sphere with a thickness of a few meters that would completely encompass the star. But, as shown by my former physics student Brooks Harrop, that design is not practical, as it would require too much matter to build and too much energy to stabilize. If such a structure were built around our Sun at Earth's distance, the sphere would likely collapse from its own gravity, and would require more solid material to build than could be scraped together in our entire Solar System.
Today Dyson Spheres are envisioned more as networks of orbiting solar power satellites that would capture most or all of the star’s energy output. If this could be done with great efficiency, the total energy gain would easily be many trillion times larger than all of our current energy consumption on Earth. But detecting Dyson Spheres around other stars is challenging, and might not be possible given today’s technology.
Wright and Povich gave it a try anyway. They used data from NASA's Wide Field Infrared Survey Explorer (WISE) to search for the expected waste energy in mid-infrared wavelengths that should be emanating from a Dyson sphere, and found nothing. (Freeman Dyson himself also suggested looking for the trails of ionized gases that would be expected from spacecraft slowing down near the mega-structure.)
If such colossal structures exist, their discovery would be mind-boggling, and would prove the existence of a civilization far more technically advanced than our own. So despite the disappointing results to date, the search seems worth continuing.