The Fermi paradox is an argument to conclude that the absence of intelligent life form technologically developed other than the human species in the Galaxy. Two members of the Pennsylvania State University point to what they see as a flaw in the reasoning of Fermi: the failure to take into account the sustainable development.

The image is legendary. In 1950, when they are busy designing the hydrogen bomb, Enrico Fermi and Edward Teller lunch with some colleagues at Los Alamos. The conversation relates to the possibility that the UFOs starting to defray the chronicle in the United States are indeed extraterrestrial machines able to cross the wall of the light.

Accustomed to quick estimates of orders of magnitude in physics, Fermi soon to estimate how long it would take for a civilization in the Galaxy growing by an exponential law to settle all the stars, even moving at a tiny fraction of the speed of light.

His conclusion seems to have no appeal. One would need less than one hundred million years, probably even one million years if a tenth of the speed of light can be achieved, which is not unthinkable when considering projects such as using Daedalus thermonuclear explosives.

But even then, we knew that the age of the Universe and in particular the Milky Way would be more than a few billion years. If we imagined the appearance if only some of extraterrestrial civilizations in the Galaxy during this time, they have largely had the time to create a galactic empire of which we would be a part. Or atleast, constructions from successive empires in the Milky Way should be everywhere around us in the solar system. Fermi then exclaimed: “But where are the extraterrestrials? .

For decades, proponents of contacts between ET and humans are struggling to escape the pessimistic conclusion resulting from the argument from the known Fermi paradox.

One of the last avatars of this debate stems from an article published on Arxiv by Jacob Haqq-Misra and Seth Baum. For them, the same exponential growth is impossible on Earth and that, increasingly, we are faced with the constraints of sustainable development, an empire throughout the galaxy also meet these limits, forcing Civilizations to slow down their expansion and prohibiting a comprehensive settlement of the Galaxy.

A civilization could not control its progression?

The concept is interesting but unconvincing …

It assumes a civilization trying to colonize the galaxy should necessarily see an exponential increase in its population and use of resource. This seems absurd.

It is not difficult to imagine a developed civilization which will also limit its population living on every planet of its primary system and leave the study and supervision of others with a fleet of Von Neumann machines. It may very well consider a population of one hundred thousand people by a habitable planet for example.

Moreover, if we raised the hypothesis of the existence of hundreds of technologically developed civilizations in the Galaxy last few billion years, even if each of them one-tenth of colonizing the Galaxy it is not immune to the argument of Fermi. Extreme rarity of the technologically developed intelligent life in space and time, or so seems the most likely hypothesis on the scale of a galaxy.

The arguments of Misra and Baum would be more convincing if they were accompanied by numerical calculations, even simple, in a model of colonization, but they did not give any.

The Fermi paradox