When it comes to thinking outside the box, Nikolai Kardashev is your man. In 1963, the then 31-year-old Soviet astrophysicist ranked hypothetical extraterrestrial civilizations in terms of their energy use with what is now known as the "Kardashev classification scheme." His interest was SETI, the Search for Extraterrestrial Intelligence using radio telescopes — specifically, he wanted to know what sort of signal might identify an advanced alien culture. How advanced? That's where the expansiveness of his thought comes in. In a landmark scientific paper, he speculated on three types of extraterrestrial civilization.
A Type I civilization ("planetary") harnesses energy at about the same rate as we do on Earth, specifically (in 1963) 4 trillion watts.
A Type II ("stellar") civilization is capable of capturing all the energy output of its parent star. Think of a Dyson sphere — a gigantic spherical shell constructed around the sun to intercept 100 percent of its energy.
A Type III ("galactic") civilization has the capacity to harness the energy of its entire galaxy.
Later thinkers have found it convenient to amend Kardashev's Type I. Instead of the 4 trillion watts he used (global energy use has quadrupled since 1963), it's more useful to think of a Type I civilization as having the capacity to utilize the equivalent of the sum total of sunlight falling on Earth. In round numbers, our planet intercepts one-billionth of the sun's energy, while our current energy use is one-millionth of that. (Most energy comes from fossil fuels at present, but we're slowly learning to better exploit renewable solar power — we now waste 99.99 percent of available sunlight.)
Back to SETI. Kardashev reasoned that we should be able to discover Type II civilizations in our own galaxy, since whatever the ETs do with all the energy they garner from their sun, the frequency of that energy will inevitably be downshifted, according to the Second Law of Thermodynamics (entropy). A Dyson sphere around a star would glow in the infrared, and thus be detectable by radio telescopes; if astronomers discover a huge, softly glowing "star," they might have found an advanced alien civilization.
The flaw in all this, of course, is to equate "advanced" with "increased energy use." We tend to make that assumption on Earth, where, for example, the U.S. per-capita use of energy is 20 times that of Cambodia, and thus we might give ourselves a pat on the back for being more advanced. But the times are a-changing, and as we start to prioritize conservation and efficiency, perhaps reduced energy use is a better metric of how far we've come. Maybe those civilizations sought by the SETI community have turned the whole "advanced corresponds to more energy use" assumption on its head by figuring out how to thrive on minuscule power.
Now in his 80s, Nikolai Kardashev is still active as the deputy head of the Russian Space Research Institute in Moscow. I wonder what he thinks of all the speculation he's generated.
Barry Evans (firstname.lastname@example.org) fantasizes about living in a Kardashev Type 0 civilization. His Field Notes anthologies are available at local bookstores.