Is energy consumption a good way to measure a civilization? The Soviet astronomer Nikolai Kardashev thought so, using it as the basis for his famous classification scheme. A Type I civilization could harness the energy resources of its home world, while a Type II could use its own star’s entire energy output. A Type III, the most exotic of all, could tap the energy of an entire galaxy, making it a plausible SETI target if we assume we can identify its exotic activities for what they were.
But some are questioning whether energy consumption is the best marker for looking at possible extraterrestrial cultures. Zoltan Galantai (Technical University of Budapest) notes that expecting vast energy use may simply be the marker of an adolescent technology, one that assumes all possible futures will look something like our own present extrapolated forward. He points out as well that there is no fast correlation between energy consumption and the spatial growth of a civilization.
If that one draws you up short (and it did me, for a time), think of it this way: a civilization might explore and populate its entire solar system without ever attaining Kardashev Type I status. For that matter, interstellar colonization might be feasible in some scenarios without becoming Type I. Consider a gradual expansion into the Kuiper Belt and Oort Cloud, followed by slow, millennial migration through Oort debris all the way to the cometary field that presumably surrounds the Centauri stars. Perhaps an entire galaxy might be colonized without achieving Type III, a defensible position given our lack of examples.
Galantai suggests an alternative metric for civilization’s growth, one based on risk. It’s much closer to home, because in its early stages it applies to civilizations that have not left the surface of their home planets. Galantai Type I is unable to survive a local disaster (think of the Anasazi, unable to overcome the loss of their forestry resources). Type II is a culture unable to survive a regional catastrophe, such as a super volcano or an ice age. Type III is threatened only by global disasters, such as climatic collapse or an impact by a sufficiently large asteroid or comet (or, of course, a combination of such events).
And so on up the scale to Galantai Type IV, in which we’ve colonized the Solar System but are still vulnerable to such things as a nearby supernova explosion, and finally to Type V, in which we move out into the galaxy, becoming all but indestructible by any one event but subject to species individuation as the vast distances between the stars separate us into separate enclaves. “Not homo sapiens,” writes Galantai, “but their descendants will spread, and the traditional idea of ‘civilization’ will become meaningless.”
There is even a theoretical Type VI, in which a civilization has colonized its entire universe. Here the author quotes Freeman Dyson’s 1979 question (in an paper in Reviews of Modern Physics), asking whether “…converting matter into radiation and causing energy to flow purposefully on a cosmic scale, we could break open a closed universe and change the topology of space-time.” Galantai’s take:
Supposing that the known laws of physics will not change in the future, it seems to be enormously improbable that even a super civilization will be able to connect the distant parts of our Universe and will be able to harmonize its endeavors to use the energy sources. But there is nothing to prevent a civilization populating galaxies after galaxies if they have enough time, while regarding their technologies, there is not an inevitable difference between those who conquered ‘only’ a galaxy and those who inhabited the entire Universe.
It’s quite an interesting notion, one that suggests not only that galaxy-spanning cultures are unlikely after Kardashev Type I, but that an advanced civilization may well conquer its own solar system and nearby stars before ever reaching the technical level needed to construct a Dyson sphere. The upshot: “An advanced civilization has to expand (as [Krafft] Ehricke points out), unless they want to die out because of a planetary cataclysm. So it is reasonable to use a scale which is based on an intelligent race’s spatial expansion, since it can show their ability to survive a disaster.”
The paper, available online, is Galantai, “After Kardashev: Farewell to Super Civilizations,” and Centauri Dreams‘ take is that whether the author is right or wrong, it’s about time someone questioned the ‘inevitability’ of large scale structures as the markers of advanced civilizations. The universe is too curious a place to lock ourselves into any single future, no matter how entertaining or plausible our preconceptions.
The complete Dyson reference above is “Time Without End: Physics and Biology in an Open Universe,” Reviews of Modern Physics, Vol. 51, No. 3 (July 1979), pp.447-460, with abstract here.