At first, this article seems like a bit of a downer:
Search for advanced civilizations beyond Earth finds nothing obvious in 100,000 galaxies — ScienceDaily.
After searching 100,000 galaxies for signs of highly advanced life, a team of scientists has found no evidence of advanced civilizations there. The idea behind the research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization’s technologies would be detectable in mid-infrared wavelengths.
…”Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, space flight, communication, or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” Wright said. “This same basic physics causes your computer to radiate heat while it is turned on.”
Theoretical physicist Freeman Dyson proposed in the 1960s that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. It was not until space-based telescopes like the WISE satellite that it became possible to make sensitive measurements of this radiation emitted by objects in space.
However, somewhat contradicting the title of the article and its opening passage, we have this snippet:
Wright reports, “We found about 50 galaxies that have unusually high levels of mid-infrared radiation. Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes, or if it could indicate the presence of a highly advanced civilization.”
I’m not entirely sure what to make of this passage given the apparent contradiction, but it sounds like we have 50 possible candidate galaxies for advanced civilizations. (Emphasis on the word “possible” here.)
Based on the information the article provides, it seems obvious that the scientists were looking for Type III civilizations on the Kardashev scale. A Type I civilization has harnessed all of the energy on its native planet. (We’re not a Type I civilization yet). A Type II civilization has harnessed all of the energy of its native star, possibly using concepts like Dyson spheres or swarms. And a Type III civilization will have harnessed all of the energy in its galaxy, or, at least for purposes of this study, enough to be noticeable across intergalactic distances.
Of course, we have no real idea how possible a Type III civilization actually is. It would involve engineering on scales that currently seem hard to imagine. But given enough time (think hundreds of millions of years), there doesn’t seem to be anything in the laws of physics that prevent it. We also can’t be sure that some observed astronomical phenomena that we’re chalking up to nature might not turn out to be mega-structures created by extraterrestrial intelligence.
But given the age of the universe, and the fact that there’s no evidence of Earth ever having been colonized in its 4.5 billion year history, it seems likely that if there are advanced civilizations out there, they’re too far away to have reached us yet. 50 out of 100,000 galaxies sounds like about the right number. The nearest advanced civilization may be several hundred million light years away.
Unless they find natural explanations for the high levels of mid-infrared radiation. Then the closest advanced civilization might might be billions of light years away, or even outside our visible universe.