The tricky part will be ruling out galaxies that appear red simply because they lie far across the universe and their light has been highly redshifted by cosmic expansion. But those distant galaxies should have sizes and spectral signatures that would help rule them out. By finding objects that have the right signature in WISE’s four infrared bands, Wright’s team hopes to be able to home in on those that could be whole galaxies full, or at least half-full, of stars with surrounding Dyson spheres.
“If every star is half-covered, or if half the stars are covered, that works out just fine,” says Wright. Like Carrigan, he’s convinced that half-full galaxies will be rare because the theoretical time to colonize an entire galaxy should be relatively short. To happen across a galaxy that’s only half-populated with Dyson-sphere builders, he says, would be like picking one human being at random out of a hundred and ending up with an infant.
The second part of Wright’s efforts will be another search for Dyson spheres within the Milky Way Galaxy. The team will be looking for individual stars that appear exceptionally red. But the quest will be complicated. “We’re going to have to worry about things that are dusty” to weed out spurious cases, explains Wright. “We’re going to have to catalog where the dust is and look for the outliers.” In the end, he says, they will have a list of objects that are “redder than any natural astrophysical object.”
Are we alone?
After the two-year project and its companion searches are over, what if nothing has turned up? What if there’s no sign of either Dyson spheres or Dyson-filled galaxies?
Wright says there could be a few different explanations. One obvious possibility is that we really are alone in the universe. Of course, we’ll never know this for sure because some life-bearing planets may never develop an advanced civilization.
But there might be other, more life-affirming reasons. “It could be that there is life in the universe, and it didn’t end up using most of the available energy [by harnessing a whole star’s light],” says Wright. “If in a billion years we’re still around but only using about 1 percent of the Sun’s light — if that’s normal, if civilizations never use more than a small percentage of their star’s light — then we’ll never detect them.
“I don’t really understand how that could be,” adds Wright, who is convinced that any technological civilization inevitably will gobble most of its star’s energy output. “But that could be, and the universe could be filled with civilizations and we won’t detect them.” Alternatively, he says, “It could be that there’s cool new physics that we haven’t discovered — ways to get rid of waste heat with neutrinos or something” that would not emit the expected infrared signal.
Of course, if nothing at all shows up in any of these new or planned searches, says Wright, “The simplest explanation would be, they’re just not out there.”