General Discussion

IF:
1. Life is a dissipative structure as described by Ilya Prigogine: organisms live by applying exergy to environmental raw materials to obtain the necessities for survival;

2. Life develops according to the self-organization principles of Non-Equilibrium Thermodynamics or NET (per Eric Schneider and James Kay);

3. Life has the NET principles embedded in its genetics (my contribution, but it seems logical). Those principles include the growth of self-organization and complexity in the presence of suitable energy gradients, and system persistence and metastability achieved through reproduction;

4. Life develops primarily on planets with a carbon/oxygen environment. The carbon/oxygen combination is a highly probable context for life due to the well-controlled exothermic reactivity of the combination, as well as the solubility of carbon compounds in water, which would also necessarily be abundant in such an environment;

5. Life evolves by means of natural selection though the application of the Maximum Power Principle described by H. T. Odum;

6. Life evolves enough to develop analytical intelligence; and

7. The intelligent life probably develops a technological civilization. Necessary (but not sufficient) conditions include a quantity of carbon stored earlier in the planet's history to provide a strong but controllable gradient of low-entropy thermal energy from combustion, and accessible metals (the raw materials of civilization) in the upper layer of the the planet's crust.

THEN:
1. If there is insufficient stored carbon available, the species will not be able to develop a technologically advanced society due to insufficient energy for the development of enough complexity. As a result it will not send radio waves out into the universe, and we will never detect its existence.

2. If there is sufficient stored carbon available, the species will inevitably destroy itself. The destruction will probably happen either through depleting some essential, irreplaceable resource (i.e. hitting a Liebig Limit) or more likely due to hysteresis in the combustion energy system. The hysteresis is the time it takes after CO₂ has been released into the planet's atmosphere until planetary warming becomes apparent.

Burning carbon and using the released energy of combustion is easy and obvious. It will be discovered fairly early in the development of the presumed intelligent species, well before they acquire enough scientific ability to detect the long-term planetary danger of the carbon dioxide exhaust gases. In our case we have been using fire for half a million years, but figured out the problem of global warming barely a hundred years ago. Until 1900 it was generally assumed that the release of CO₂ was existentially benign.

By the time the danger is realized, the species will be carbon-dependent - locked into the burning of carbon for energy - trapped in a vicious spiral of thermodynamically-driven self-organization, energy-dependent maintenance of existing physical and social structures, increasing energy dependence, increasing CO₂ production - and increasing planetary heating from the "greenhouse effect". The more carbon-dependent the species becomes, the harder it is to break free from that dependency.

If there is enough carbon available, the species will become technologically advanced, will send out signals for a short while and will then probably encounter an inability to adapt to the planet's changing climate. The species will not climb out of its gravity well and fly to the stars, because the energy required will all be soaked up in its own growth, and extinction will happen well before it gets to the Dyson Sphere stage.

Now, I may be anthropomorphizing like crazy, but the whole theoretical edifice rests on the fairly banal assumption that our experience is approximately average for an intelligent species. That is, we are not the least bit special. Similar intelligent life will probably arise under similar conditions, follow a similar path (though different in the details) and fall into a similar hole. The details will differ, but I think the trajectory will be similar.

Where is everybody? Well, there are probably a lot of them out there. But either they never developed radio, or they did and soon afterwards all went the same place we're probably going: Poof!