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


15.1  Type I Civilizations:  Planetary Cultures

A primitive intelligent alien race, slowly evolving and spreading across the face of its native world, eventually will discover and utilize a wide variety of elementary energy supplies. In the beginning, such creatures would rely mainly on natural sources such as hot springs, fires set by lightning. and their own muscle power.

But soon their intelligence, and the Principle of Economy, would impel them to develop new and easier ways to generate and harness energy. They‘d learn to set their own fires, and how to control them. Animals might be harnessed for transportation, hauling, and agricultural activities. Better fuels, such as coal or natural oil secured from local tar pits, would replace wood in campfires.

On our own home planet, this early period was marked by a relatively slow growth in worldwide energy usage. The increase amounted to no more than perhaps 0.3% per year, a doubling time of about 200 years. The speed at which basic resources could be pressed into service, with primitive technology and finite manpower, was extremely limited. Such an early "incubation period" of leisurely growth should be common during the first stages of cultural evolution on any world.

It is entirely possible that ETs on some planets may call a halt, or even reverse, this upward trend in energy consumption. This does not necessarily imply an immediate halt to all technological development -- for instance, the culture may simply be shifting its attention from energy-intensive projects to information-intensive ones. However, it does place rather stringent limitations upon the material achievements to which the society may aspire. Without abundant energy, an economy of scarcity management is virtually inevitable.

Finding this prospect rather unattractive, and driven onward by the curiosity and aggressiveness that enabled them to take dominion over their world, many intelligent extraterrestrial races would seek to further improve both the sources and the distribution of power.

On Earth, the widespread initiation of fossil fuel burning (stored solar energy) provided a powerful new source of abundant energy. While great effort was required to harvest tiny amounts of power from wind and water, a tiny bit of oil or natural gas went a long way. In addition, steam and electricity came into their own during the last two centuries of human history. There was getting to be an abundance of raw energy, powerful ways of harnessing it to perform useful work, and efficient means of transmitting it over great distances. The dawn of global culture was at hand (Figure 15.2).


Figure 15.2 The Night-time View of the Eastern United States, as Seen from Space2603

Cultural Pyramid Theory of Civilization

The thermal burden of energy usage on Earth is a planetary, not local, issue.


In the last two centuries, humanity has maintained a 3% per year growth rate in energy consumption, a full order of magnitude above the early stages of cultural evolution on Earth. The doubling time is now measured in decades rather than in centuries. Let's see exactly what this means.

It is believed that the Roman Empire, at the height of its expansive construction and military activities, annually consumed power at a rate roughly equivalent to 3 x 109 watts (1 watt = 1 joule/second) . Nearly two millenia later, humanity has increased its energy usage a thousandfold. By 1975, global power consumption reached about 7 x 1012 watts. In only two thousand years, mankind's per capita energy production has leapt from about 30 watts/person in ancient times to nearly 2000 watts/person today.

Xenologists want to know whether or not energy usage will also increase exponentially among alien cultures, as it appears to have done here. Perhaps more interesting and germaine, however, is the following related query: Are there any limits to growth, assuming the ETs adopt an expansionist philosophy?

It turns out, not surprisingly perhaps, that there do exist very definite limits to growth for any culture that remains confined to the surface of a single planet. There are three fundamental factors which delimit the quantities of energy accessible to a sentient race: (1) availability; (2) efficiency; and (3) planetary carrying capacity.

Our first consideration is the availability of a given energy resource. In general, sources compete with one another depending on their relative scarcity. or abundance. To take one trivial example, an alien culture located on a world with little water and strong winds might be expected to place greater emphasis on the development of windmills rather than waterwheels or dams.

A corollary to the fact that a civilization is planetbound is the inevitable finiteness of all resources. There is only so much wind, water, geothermal steam, wood, fossil and nuclear fuels at the surface of a world. Once the population of an extraterrestrial culture has expanded to the point where these resources are in danger of exhaustion, the civilization faces drastic modification, degeneration, or possibly even extinction on a global scale. Such is the early and quite predictable result of sole reliance upon nonrenewable sources of energy.

Fortunately, there exist two sources which should be available to all ET societies and which are virtually inexhaustible. First, there is nuclear fusion. This involves mashing together two atoms (usually of hydrogen) which yields a single heavier atom plus lots of energy. About one hydrogen in every 6000 in ordinary seawater is deuterium, the most likely hydrogen isotope to be used in controlled thermonuclear power generation. It is estimated that if all the deuterium in Earth's seas were collected and burned in fusion power stations, it would supply all our energy needs at the present rate of consumption for the next 5-10 billion years -- roughly the expected lifetime of Sol.

An alien civilization that opts for fusion power may expect to have enough energy to endure over geological timescales provided there is no growth. If there are oceans of water sufficient to spawn life, there will probably also be enough deuterium to provide all "Type I"* planetbound cultures with virtually inexhaustible energy.**

The other major energy source available to planetary cultures is solar power. Unless blocked by a thick cloud cover, filtered out by the atmosphere, or attenuated by great distances, radiative energy from the stellar primary can serve as a bountiful and virtually infinite "renewable" source of power. Since stars in habitable solar systems may be expected to have lifetimes measured in eons, a Type I extraterrestrial civilization could again expect a long healthy existence before its energy supply ran out.

So on the question of availability, a large-scale Type I planetary culture should ultimately benefit most from either deuterium fusion power or solar fusion power.

The second consideration involves the question of the efficiency of the particular energy resource chosen. Since the technology of a civilization limited to the surface of a single world will ultimately experience severe restrictions on its finite resources, it is important to make the best use possible of what little is available.

Earlier in this century, the late Albert Einstein demonstrated that mass and energy are interchangeable. According to the famous E = mc2, a given amount of matter (m) is exactly equivalent to a certain quantity of energy (E). (The constant of proportionality, c2, is the speed of light, squared.) All energy, whether from fusion, fission, or chemical reactions, ultimately derives from the conversion of a tiny bit of matter into heat, light, sound, etc.

If their civilization is to long endure, ETs must find the most efficient means for converting mass into energy. Table 15-l provides a representative sampling of various common and theoretical energy sources available to Type I planetary cultures on any world in our Galaxy. In each case the efficiency is calculated, based on the fraction of matter which is changed into usable energy. The most efficient is "total conversion" (100% of the matter goes to energy), but it is difficult to imagine the cheap production of sufficient quantities of antimatter to make this process competitive with thermonuclear fusion.


Table 15.1 Conversion of Matter into Energy:
A Comparison of Efficiencies

Fuel Efficiency
(Fraction of Reaction Mass
Converted into Energy)
per Unit Mass
0.000000007 %
6.3 x 106
0.000000021 %
1.9 x 107
   Bituminous coal
0.000000036 %
3.2 x 107
   Fuel oil
0.000000052 %
4.6 x 107
   Hydrogen, liquefied
0.00000016 %
1.4 x 108
   U235 —> decay products
0.085 %
7.7 x 1013
   Hydrogen —> helium
0.7 %
6.3 x 1014
   Hydrogen —> iron
0.9 %
8.3 x 1014
   Matter —> antimatter
100.0 %
9.0 x 1016



Indeed, fusion appears to be the most efficient energy generation technique for which the fuel is exceedingly abundant. Once again, both deuterium fusion power and solar fusion power qualify as most efficient. So on the basis of the two factors we‘ve looked at, it is a pretty sure bet that advanced Type I alien cultures will adopt either or both of these techniques.

But even using the most efficient, abundant sources of energy, planetbound societies cannot continue to expand indefinitely. This is because of the third critical limiting factor: Planetary carrying capacity. The history of our own planet is typical.

In the past century, world energy production has escalated at an average rate of 3% per annum. Approximately every twenty years, human power consumption doubles. In 1975 we used 7 x 1012 watts. If the historical 3% growth rate is maintained, then by the year 2300 A. D., mankind's energy budget will be up to 2 x 1017 watts. Why is this significant? Simply because 2 x 1017 watts is also the total power received from Sol on planet Earth. To sum up, by 2300 A.D. humanity will be generating as much energy artificially as is received at the planet's surface from its sun (Figure 15.3).

We will then face the most critical "energy crisis" in the history of Earth. Rather than a crisis of scarcity, however, it will be a crisis of overabundance.


Figure 15.3 Curve of Growth of Technological Energy Usage for a Typical Emergent Type I Civilization: Humanity

Cultural Pyramid Theory of Civilization

Calendar Year


All forms of energy -- electrical, thermal, mechanical, nuclear -- ultimately return to the biosphere in a single degraded form: Heat. Such thermal pollution can rapidly reach catastrophic proportions. As more and more energy -- heat -- is liberated at the planetary surface, the global temperature begins to rise and the precarious energy balance of the biosphere begins to suffer irreversible damage.

At what point in the development of a Type I civilization will this ultimate "hypsithermal catastrophe" occur? Certainly by the time artificial energy production equals total solar influx, the planet will have suffered serious ecological damage.29 Earth, for instance, would no longer be inhabitable by humans, our lush green world converted into a stewing, steamy hellhole much like Venus. Most experts believe that irreversible destruction of environmental equilibrium would occur at far lower levels of energy production. Conservatives usually draw the line at the photosynthetic energy limit, or the total solar energy fixed by green plants worldwide. This is only about 4 x 1013 watts.

The best guess seems to be about 1% of the total solar influx as the critical limit.29,688 This is about 5% Of the energy stored in Earth's hydrosphere, and would probably be sufficient to melt the polar icecaps and thoroughly disrupt the entire ecology. On planets with smaller oceans, or with non-water oceans, the climatic turnover point might occur far sooner.

We estimate, therefore, that the maximum upper limit of artificial energy generation for any Type I planetary culture limited to a single world in our Galaxy is roughly 1015 watts.


* Dr. N.S. Kardashev, a well-known Russian astrophysicist currently associated with the Institute for Cosmic Research at the Soviet Academy of Sciences in Moscow, devised a particularly fruitful classification scheme which includes all conceivable ET civilizations and is based on system-wide energy consumption.1320 However, Kardashev limited his analysis to the energy available for the purpose of interstellar communication between alien cultures. In this book the original concepts are broadened to provide a general taxonomy for all extra-terrestrial civilizations -- whether communicative or not.

** Cultures native to planets with ammonia or methane oceans similarly will have an abundance of deuterium fusion fuel at their disposal. Inhabitants of worlds with sulfur or liquid carbon dioxide seas will not be so fortunate.


Last updated on 6 December 2008