The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilization and humanity's lack of contact with, or evidence for, such civilizations. The basic points of the argument, made by physicists Enrico Fermi and Michael H. Hart, are:

• The Sun is a young star. There are billions of stars in the galaxy that are billions of years older;
• some of these stars likely have Earth-like planets which, if the Earth is typical, may develop intelligent life;
• presumably, some of these civilizations will develop interstellar travel, a technology Earth is investigating even now;
• at any practical pace of interstellar travel, the galaxy can be completely colonized in a few tens of millions of years.

According to this line of thinking, the Earth should already have been colonized, or at least visited. But no convincing evidence of this exists. Furthermore, no confirmed signs of intelligence elsewhere have been spotted, either in our galaxy or in the more than 80 billion other galaxies of the observable universe. Hence Fermi's question, "Where the heck is everybody?"

Here's my answer to the Fermi Paradox, which is based on the way life evolves based on thermodynamic principles. Let's start with the following assumptions about life in general (you may notice some familiar aspects).

IF:

1. Life is a dissipative structure as described by Ilya Prigogine: it lives 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 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 (H₂O) - which would also necessarily be abundant in such an environment;
5. It evolves by means of natural selection though the application of the Maximum Power Principle described by H. T. Odum;
6. It evolves enough to develop analytical intelligence; and
7. The intelligent life 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 controlled gradient of low-entropy thermal energy from combustion, and accessible metals 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. this will happen either through depleting some essential resource (i.e. hitting a "Liebig Limit") or more likely due to hysteresis. The hysteresis comes from 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 done fairly early in the life of the presumed intelligent species, well before they accumulate enough scientific knowledge to detect the long-term planetary danger of the carbon dioxide exhaust gases.  In our case we have been doing it for over a million years, but figured out the problem of global warming less than a hundred years ago.

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".

If there is enough carbon available, the species will become technologically advanced, will send out signals for a short while and will then go extinct due to 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'm probably anthropomorphizing and projecting like crazy, but the whole edifice rests on the fairly banal assumption that our experience is approximately average for an intelligent species. That is, we are not in the least special. Other intelligent life will probably arise under similar circumstances, follow a similar path and fall into a similar hole.

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!  Thank you, physics!