Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm


15.2  Type II Civilizations:  Stellar Cultures

In the earliest stages of social evolution, alien societies will be pretty much restricted to the surface of their planet. Type I civilizations are de-fined as those which consume power at the carrying capacity of the planet. Such cultures are limited to the energy obtainable on a single world.

We've seen that planetbound societies can have a long and healthy existence, and may expect to survive for eons barring some unusual major global catastrophe of some kind. But this imposes rather stringent limits to growth on planetary cultures. The price that must be paid for stability and long-term survival on the limited surface of a single world is energetic stasis. This may well lead to cultural stagnation.

Alien races may discover that the only escape from this trap is to move out into space. A Type I society will remain one forever, until and unless it becomes spacefaring.

With the first flights of the American space shuttle, humanity has taken the first tentative step in the evolution from a planetbound Type I to a space-faring Type II stellar culture. In the centuries to come, space industrialization will proceed with vigor as man becomes more aware of the countless ad-vantages of space-based manufacturing. Of these, the two most highly significant benefits for long-term, large-scale heavy industrial development are vast size and vast energy.

First, whether in orbit around the home planet or swinging freely in circumsolar territory, physical stresses on material structures are always minute. For this reason, giant artifacts which would be impossible on the surface of a planet will be commonplace in space. Flimsy constructions many tens of kilometers in diameter are possible even with present-day human technology! Huge factories and physical plants may be assembled. Once manufacturing activities in orbit reach a point of relative self-sufficiency -- a kind of economic "critical mass" -- .further expansion will be breathtakingly rapid.

Second, habitats lofted to planetary or solar orbit will find a vast abundance of solar energy. A single world intercepts only a tiny fraction of the entire solar output, less than one one-billionth of the total. But the spacefaring Type II civilization can collect energy from anywhere on a theoretical spherical shell surrounding the central star -- a potential energy preserve perhaps ten or eleven orders of magnitude greater than that available at the surface of the home world.

The swarm of technological artifacts orbiting in successive shells around the primary will grow thick as development proceeds. These space factories and habitats ultimately will enclose and capture virtually the entire stellar energy output. This amounts to what xenologists usually call a "Dyson Sphere." Originated by Freeman Dyson at Princeton, the Dyson Sphere is the end result of full space industrialization by a Type II civilization. An almost solid sphere of artifacts envelops the sun, absorbing and directing each watt to the purposes of the gargantuan interplanetary industrial complex.

But even solar energy is not limitless. All spacefaring cultures ultimately must run afoul of the "Dyson limit" -- the sum total of all energy emitted by the home star. This is, in some sense, the "carrying capacity" of the entire solar system. Even if the jovian planets are disassembled and cannibalized for fusionable hydrogen, the Dyson limit cannot be much exceeded without sacrificing cultural longevity (e.g., by cannibalizing the home star itself).

How long will it take for an intelligent species to evolve from a planet-bound Type I culture to a spacefaring Type II civilization pressing fitfully against the Dyson limit?

A typical sun of the habitable variety illuminates alien transsolar space with about 1026 watts of power. Assuming a modest 3% per year growth rate in the interplanetary industrial complex, a Type I civilization (1015 watts) could make the transition to a fully industrialized Type II civilization (1026 watts) in a mere 900 years. Even if we take the incredibly conservative primitive growth rate of 0.3% per year, the transition is accomplished in just 9000 years -- long by human standards but only the wink of an eye on geological and evolutionary timescales. We know that it has taken humanity about 10,000 years since the invention of agriculture and basic toolmaking to build a planetary culture, so the estimates above are certainly reasonable.


Last updated on 6 December 2008