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Fermi's Paradox

The galaxy contains roughly a hundred billion stars. If even a very small fraction of these have planets which develop technological civilizations, there must be a very large number of such civilizations. If any of these civilizations produce cultures which colonize over interstellar distances, even at a small fraction of the speed of light, the galaxy should have been completely colonized in no more than a few million years [1]. Since the galaxy is billions of years old, Earth should have been visited and colonized long ago. The absence of any evidence for such visits is the Fermi paradox.

articles & documents

"Where Is Everybody?": An Account of Fermi's Question

Eric M. Jones, Los Alamos National Laboratories

Fermi's Famous question, now central to debates about the prevalence of extraterrestrial civilizations, arose during a luncheon conversation with Emil Konopinski, Edward Teller, and Herbert York in the summer of 1950. Fermi's companions on that day have provided accounts of the incident. R

Fermi's Paradox and the Preparation for Contact Hypothesis

Bernard Haisch, Ph.D.

There are at least 100 billion, and perhaps as many as 400 billion, stars in our Milky Way Galaxy. Carl Sagan once said: "There may be a million worlds in the Milky Way Galaxy alone which are at this moment inhabited by other intelligent beings" (Cosmos, episode XI). R

Fermi's Paradox I: Our Galaxy Should Be Teeming With Civilizations, But Where Are They?

Seth Shostak, Astronomer, Pheonix Project

Is there obvious proof that we could be alone in the Galaxy? Enrico Fermi thought so -- and he was a pretty smart guy. Might he have been right? R

Fermi's Paradox II: What's Blocking Galactic Civilization? Or Are We Just Blind To It?

Seth Shostak

Could galactic empires exist? In a previous article, we noted that there has been plenty of time for aliens keen on colonizing the Milky Way to pull it off. However, we see no signs of galactic federation ("Star Trek" aside). Why does the cosmos look so untouched and unconquered? What is keeping advanced extraterrestrials from claiming every star system in sight? R

Fermi's Paradox III: Zookeepers, Alien Visitors, Or Simple Life; How Can We Explain Our Isolation?

Seth Shostak

We seem to have the Galaxy to ourselves. At least, that’s the obvious conclusion from the apparent lack of aliens in the neighborhood. But this conclusion might be a bit too obvious, and possibly wrong.  R

Refuting Fermi: No Evidence for Extraterrestrial Life?

John B. Alexander, Ph.D.

In a recent article Seth Shostak drew attention what has become known as the Fermi Paradox. Typically discussants raise the famous off-hand luncheon comment by Enrico Fermi, "Where is everybody?" when dismissing the existence of intelligent extraterrestrial life. The invocation of such a distinguished figure is polemic and used to make the position academically unassailable.  R

SETI, the Fermi Paradox and The Singularity: Why our search for extraterrestial intelligence has failed

John Faughnan

This paradoxical failure is sometimes called "The Great Silence". The Great Silence suggests that space traveling technological civilizations are extremely rare (or very discrete [8]). There have been a number of explanations for the why such civilizations might be rare. I list three explanations below. You can choose the one you like; they are as close to destiny as we are likely to get.

So Where Are They?

Richard Harter

One of the questions bruited about in SF circles is the Fermi paradox: Where are the aliens? In a universe with billions of galaxies, galaxies having a hundred billion stars, it is implausible that this planet is the only abode of intelligent life, that there aren't quite a few planets around with intelligent life forms on them. R

The Fermi paradox

Nick Bostrom, Dept. of Philosophy, London School of Economics

There has been much speculation around Fermi's famous question: "Where are they? Why haven't we seen any traces of intelligent extraterrestrial life?". One way in which this question has been answered (Brin 1983) is that we have not seen any traces of intelligent extraterrestrial life because there is no extraterrestrial life because intelligent extraterrestrial life tend to self-destruct soon after it reaches the stage where it can engage in cosmic colonization and communication.

The Fermi Paradox: An Approach Based on Percolation Theory

Geoffrey A. Landis, NASA Lewis Research Center

I propose a model for [for the problem of the Fermi Paradox] based on the assumption that long-term colonization of the galaxy proceeds via a "percolation" process similar to the percolation problem which is well studied in condensed-matter physics. Rather than assuming a uniformity of motive for extraterrestrial civilizations, the model assumes a wide variety of motives, with a mixture of civilizations interested in colonization and "stay at home" civilizations. R

The Possibilities of FTL: Or Fermi's Paradox Reconsidered

F.E. Freiheit IV

The drive to place humanity at the center of the universe has led to a stream of assumptions that, as facts have been collected, are shown to be ill founded. The Ptolemaic Earth centered view was replaced by Copernican Sun centered view which in its time was also replaced. The assumption that we are alone in the universe is also under threat of replacement. One of the more interesting aspects of our apparent aloneness was pointed out by Enrico Fermi and is know as Fermi's Paradox (1). R

Where Are They? Maybe we are alone in the galaxy after all

by Ian Crawford, Scientific American, July 2000

How common are other civilizations in the universe? This question has fascinated humanity for centuries, and although we still have no definitive answer, a number of recent developments have brought it once again to the fore. Chief among these is the confirmation, after a long wait and several false starts, that planets exist outside our solar system. R

websites & organizations

Book: Where Is Everybody?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life

Stephen Webb

In this lively and thought-provoking book, Stephen Webb presents a detailed discussion of the 50 most cogent and intriguing answers to Fermi's famous question. The proposed solutions run the gamut from the crackpot to the highly serious, but all deserve our consideration. The varieties of arguments -- from first-rate scientists, philosophers and historians, and science fiction authors -- turn out to be astonishing, entertaining, and vigorous intellectual exercises for any reader interested in science and the sheer pleasure of speculative thinking.


Where Is Everybody?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life Stephen WebbDuring a lunchtime conversation at Los Alamos more than 50 years ago, four world-class scientists agreed, given the size and age of the Universe, that advanced extraterrestrial civilizations had to exist. The sheer numbers demanded it. But one of the four, the renowned physicist and back-of-the-envelope calculator Enrico Fermi, asked the telling questions: If the extraterrestrial life proposition is true, he wondered, "Where is everybody?"" "In this book, Stephen Webb presents a detailed discussion of the 50 most cogent and intriguing answers to Fermi's famous question. Buy from Amazon Buy from Barnes & Noble more info...