The Fermi Paradox Part 1

by Duncan Lunan

Alan Bean ‘Where is everybody’

Between 1982 and 1990, Leslie Banks, IBM’s head of scientific public relations, organised nine extraordinary events, beginning with ‘Science and the Unexpected’ at the Heathrow Hotel in March 1982.  These ‘Heathrow Conferences’ brought together galaxies of top scientists, UK and world figures, to review the cutting edges and the controversies in a wide range of scientific fields.  Without looking at my files, names that come to mind include Sir Hermann Bondi, Prof. Jacob Bronowski, Prof. Richard Dawkins, Dr. Richard Garwin, Prof. Thomas Gold, Prof. Stephen Jay Gould, Prof. Richard Gregory, Sir Fred Hoyle, Dr. Garry Hunt, Dr. Sergei Kapitza of the USSR, Prof. Eric Laithwaite, Prof. James Lovelock, and His Holiness the Dalai Lama.  The late Prof. Archie Roy spoke on ‘The Lamps of Atlantis’ in 1986, and I was the only amateur scientist to address a Heathrow Conference, on ‘The Fermi Paradox’ in 1987, when the theme was ‘Science and Paradox’.  My paper was published in Speculations in Science & Technology, January 1988. and updated in 2003 for Asgard.  It leads into the topic with some of the history which Prof. Michael A. Garrett didn’t include in his February lecture on the Search for Extraterrestrial Intelligence, which I summarised last week.

Enrico Fermi c.1943-49

It seems that Enrico Fermi formulated his paradox during a lunch break at Los Alamos. “Where is everybody?” he asked – meaning not his colleagues or the cafeteria staff, but the extraterrestrials who might have been expected to be present.  “Everyone knew what he meant”, the participants recall, but they had the advantage of prior discussion  (1).  The full question is, given the relative ages of the Galaxy, the Earth, and the human race, would we not expect that the galactic civilization would have already been established, and have encroached on us (benevolently, for preference) long since?

Camille Flammarion, ‘Empedocles Breaks through the Crystal Spheres’, L’atmosphère météorologie Populaire, 1888

Until recently, the answer you preferred depended on the optimism you felt about the human race itself;  or about the feasibility of interstellar travel;  or about the rarity or otherwise of life, intelligence and technology.  In the last category, the numbers are nowadays outwardly more favourable to Fermi’s argument: we now place the age of the Earth at 4,600 million years, with primates established on it for ten million, while in the disc of the Galaxy there are Population I stars like our Sun but up to twice as old  (Population I stars formed out of interstellar clouds enriched by supernova explosions, taking up the heavy elements necessary for the formation of Earth-like planets and the evolution of life.  As I’ve explained in previous articles  (‘Stars and Nebulae’, ‘The Milky Way’ and ‘The Search for Extraterrestrial Intelligence’), we now know that there could be lots of stars roughly contemporaneous with the Sun, give or take a billion years, and a much older population of sunlike stars in the thick disc of the Galaxy, dating back to 13 billion years ago.  (Population II stars [discovered later] are older still, but when they formed, to make up the galactic nucleus, halo and global clusters, the only building materials available were hydrogen and the helium formed in the Big Bang).  Those who believe that interstellar travel is possible, believe that the Galaxy could be thoroughly explored in only ten million years.  If others attempted it, it could well have been accomplished long since.

Kepler-drawing triangulating Mars position

But have there been any others?  Here opinions differ sharply.  After all, the idea that we might not be alone in the Universe is relatively new in human thought.  For most of human history we have thought that the sky was some kind of solid shell in which the stars were pierced or embedded, and for most of recorded history the planets were thought to be fixed on transparent but unbreakable concentric spheres.  Kepler’s demonstration of the ellipticity of Mars’s orbit metaphorically broke the crystal shells that enclosed us, and the plurality of worlds became established philosophical doctrine for a time.  Milton wrote of “every star perhaps a home of destined habitation” (2);  the nebular hypothesis of Kant and Laplace gave an account of the Solar System’s origin which presumably could be true of almost any star;  Herschel believed that all the heavenly bodies were inhabited, even the Sun.  At the turn of the 19th century Tsiolkovsky, in Dreams of Earth and Sky (3) looked forward to discovering extraterrestrial life with as much enthusiasm as Burton in The Anatomy of Melancholy in the early 17th century, with the only difference that Tsiolkovsky knew just how humans could “fly up…command the spheres and heavens, and see what is done amongst them”(4).  Practical discussion of Communication with Extraterrestrial Intelligence (CETI), or Search for… (SETI), as NASA prefers, might have followed, but instead the pendulum swung the other way.

The problem with the Kant-Laplace hypothesis was that it failed to account for the distribution of angular momentum in the Solar System;  98% of that angular momentum resides in the planets and only 2% in the Sun, whereas according to the Nebular Hypothesis the Sun should be rotating much more rapidly.  In the 1930s Sir James Jeans suggested that the planets had formed and gained their angular momentum in a near-collision with a passing star.  The hypothesis had far more obvious mathematical flaws than its predecessor but, nevertheless, gained widespread acceptance – possibly because it restored humans to their previous eminence at the peak of evolution in the known Universe.  A collision between stars was too rare an event to occur more than once or twice in the history of the Galaxy, and the fact that spiral nebulae were other galaxies had yet to be proved.  We could forget Tsiolkovsky’s alarming prediction that we might find “what humanity was like several thousand years ago – and what it will be like in a few million years”.

While few of them probably could have pinpointed its flaws, the emerging cadre of science fiction writers felt intuitively that the collision hypothesis was false.  In 1928, when Jeans’s reputation was about to make him the best-selling scientific author to date, E.E. ‘Doc’ Smith published an unreadable classic called The Skylark of Space, the first novel of interstellar travel.  Science fiction writers have been filling the Galaxy with inhabited planets ever since, and until 1960, the only discussion of contact with other intelligence in any form was within the pages of science fiction.

Meanwhile, the pendulum of scientific thought had been swinging again.  Growing understanding of nuclear fusion had been leading to a much better idea of what went on in the Sun and the stars, and what must happen during their formation.  Hannes Alfvén and Fred Hoyle evolved the hypothesis that during formation of the Solar System the Sun’s rotation had been slowed by magnetic interaction with the surrounding disc of ionised preplanetary material.  Angular momentum had been transferred to the planets from the Sun, and still more had been carried away by gases driven out of the Solar System altogether.  The exciting implication was that any slowly rotating star might have planets; and it was found that, whereas the more massive, short-lived stars like Sirius all rotated rapidly in a matter of hours, stars less massive than F5 (7) (just a little less massive than Procyon) had rotation periods on the order of a month, like the Sun.  The plurality of worlds was back, and seemed to be confirmed by announcements that 61 Cygni had a ‘superjovian’ planetary companion and the red dwarf Barnard’s Star had at least two planets less massive than Jupiter.  Although those candidates were later discounted, thousands of ‘exoplanets’ have now been discovered and it seems that planetary systems like our own are indeed common in the disc of the Galaxy, possibly orbiting every candidate star.

Whether the same assumption can be made about the evolution of life is another matter.  That life will arise when it has the opportunity is generally agreed, but there are major disputes about the permissible range of conditions, and even wider-ranging ones about the evolution of intelligence.  In his ‘engineer’s approach to evolution’, for instance, Alan Bond has argued that while bacteria will be found on many planets, blue-green algae will be relatively rare….and so on to a prediction that at its present age, the Galaxy supports one intelligent species, maybe two.  Since Earth hosts humanity and the cetaceans, that would take care of the possibilities (5).  In a later review of the question, Martyn Fogg’s model suggested by contrast that a million civilizations might have arisen independently in the history of the Galaxy thus far (6-8), and that estimate might now have to be increased substantially.

Frank-Drake Ozma radio-telescope, Green Bank, 1960,

The CETI issue came to a head in 1960 with Project Ozma, Frank Drake’s brief listening watch for intelligent radio signals from Tau Ceti or Epsilon Eridani.  By 1963 there was enough published scientific material for A.G. W. Cameron to collect and publish it as Interstellar Communication (9).   Extraterrestrial Civilizations appeared in the USSR in 1965(10) and Carl Sagan collected the papers of the 1971 CETI Conference as Communication with Extraterrestrial Intelligence in 1973(11).  Lunan’s Law was in operation: ‘the respectability of a scientific topic is directly proportional to the number of times it has been argued within hard covers’.

But along the line, as respectability was attained, a curious hardening of thought had taken place.  The moderate assumption underlying Project Ozma – that a nearby civilization might have detected the more powerful transmitters brought into use during the Second World War, and might be trying to attract our attention in return – had been elevated into what Freeman Dyson calls “philosophical discourse dogma”; insistence that the higher civilizations of the Galaxy communicate only by radio, refusing all other options, despite the difficulties of attracting attention unless they are near-neighbours (12).  In the second volume of Interstellar Communication, for example, published in 1974, Cameron and Cyril Ponnamperuma reprinted the Bibliography on Interstellar Communication by Eugene Mallowe, Caren and the late Robert Forward; but as Mallowe justly complained in reviewing the book, “The category of interstellar transport and propulsion methods was regrettably omitted by editorial fiat” (13)    As a philosophy graduate, I analysed and attacked the supposed ‘higher philosophy’ of radio communication in a guest chapter for Extraterrestrial Encounter by the late Chris Boyce (15). and I do not believe that advanced civilizations will find “philosophical discourse dogma” binding.

The accepted view then was that advanced civilizations are unlikely to be near-neighbours, unless by pure chance.  The most often quoted analysis is the Drake or Green Bank equation,

N = r* fsfpfeflfifcL

where N is the number of civilizations capable of interstellar communication, r*. is annual rate of star formation, and the f terms are the fractions of stars which resemble our Sun, stars which produce planets, planetary systems which have Earth-like worlds, fractions of those which produce life, intelligent life, and communicative technology – all multiplied by L, which is the average lifetime of a communicative civilization.  The lifetime term is typically put at several million years, and inserting a set of arbitrary but conservative values for the other terms gives a figure of one million advanced civilizations in the Galaxy, separated on average by 300 light years or so (15).

University of Rochester Drake Equation variant, 2016

Sebastian Van Hoerner had published a much more pessimistic assessment (16),  giving four headings under which destruction could come to an advanced civilization: destruction of all life, destruction of higher life only, physical and/or mental degeneration or decay, or simple loss of interest in science and technology.  It was all too easy for pessimists and cynics to conclude that high-technology civilizations destroy themselves in a few decades or centuries at most, just as (they argued) our own was about to do.  I have recently updated my own attempt to tackle this argument in detail (17).   Such a Politics of Survival would list the ways in which we can be wiped out, and what could be done about them, under eight headings:

1.  Weapons of mass destruction

2.   Overpopulation

3.   Pollution of the environment

4.   Exhaustion of natural resources

5.   Genetic breakdown

6.   Giant meteor impact

7.   Sun change or nearby supernova

8.   Direct contact with other intelligence (not necessarily with harmful intent)

The Politics of Survival, Duncan Lunan, 2003 (first formulated 1969)

The worst case in any of those areas of catastrophe would wipe us out entirely, as could lesser cases of two or more of them in concert (synergy).  All the single possible causes of human extinction are on the list, although one or more headings may have to be modified to encompass genetic engineering, depending on the direction taken by that research.

The first thing to notice is that the first five dangers are man-made and the last three are external, i.e. they cannot be countered effectively while we are restricted to a single planet.  Any politics of survival programme, therefore, whose final goal was the guaranteed survival of the human race, would have to include an ongoing space programme.  Specifically to deal with heading 7, we must have self-sustaining communities not located on open planetary surfaces, and drawing their materials and energy from sources other than Earth; we must also have the capability to reach and dismantle  (mere shattering will not suffice)  any asteroid which threatens to collide with Earth, that being the primary threat under heading 6.  Since the Moon mostly lacks volatiles essential for life support, and those compounds can be found in the asteroids, to deal with those headings alone the space programme must be pursued as far as the industrialization of the asteroid belt, and that objective must be met even if purely terrestrial solutions can be found for the first five problems.  Since space technology can, in fact, play a major part in solving them, and is essential to counter the other three, space-oriented solutions should be the ones adopted.  Following an Association in Scotland to Research into Astronautics (ASTRA) project Man and the Planets it seems that extinction under any of headings 1 to 7 can be rendered impossible within 150 years of space development (18).

As regards heading 8, we might hope that more advanced civilisations would have better purposes in seeking Contact.  Nevertheless, while we are confined to a single planet, the possibility of accidentally lethal harm can’t be ruled out.  At the other extreme, in one of the classic Jeff Hawke stories in the Daily Express, the Milky Way was being invaded by the Mi-Ti-I, ‘a barbarian, homeless people… from the gulf of the unknown’, presumably from outside the Local Group of galaxies, phonetically sharing their name with an expensive and very potent Indonesian liqueur called Mai Tai.  Their philosophy appeared very similar to the aliens’ in Independence Day, for which Jeff Hawke’s creator Sydney Jordan did some of the story-board work.  However, for the invaders it is a recipe for disaster.  In his guest chapter for my first book Man and the Stars, the late Chris Boyce produced a simplified version of a scenario on which he had done considerable work (19), as follow.

Chris Boyce Contact diagram

If intelligent life is sufficiently common in the Galaxy for a race like the Mi-Ti-I to get started, we may suppose that a substantial number of spacefaring races arise, at various stages of development, before interactions begin.  Suppose that a third of them are totally trusting;  a third are touchy and distrustful, like ourselves;  and a third are paranoid and destructive like the Mi-Ti-I.  The trusting can always form alliances;  the mistrustful can form alliances half the time with the trusting, and a quarter of the time with one another;  the paranoid can never form alliances;  and an alliance can always beat a singleton.  After three recursions, 60% of the trusting survive, 40% of the mistrustful survive, and all of the paranoid are gone.  The interaction diagram Chris published in Man and the Stars was a much simplified version of the very complex one he’d constructed in private research.  And it turned out not to matter how much you varied the original ratios:  after three or at most four recursions, the end result was the same.  As Chris himself succinctly put it, “Interstellar checkers is not a viable mode of existence”.  

Man and the Stars was concerned in large part with human survival on the interstellar stage. To be sure of surviving any catastrophe in class 7 or 8, we supposed that human settlements had to be spread over a radius of at least 10 light years.  We were allowing only for the ‘ordinary’ Type 1 or Type 2 supernovae, rather than the more violent Type 3 event which might have wiped out the dinosaurs at a distance of over 1000 parsecs (20).  It’s now pretty well established that the dinosaurs were wiped out by impact – one big asteroid(21) or a bombardment of comets (22).  Since publication of Man and Stars in 1974, however, the whole concept of human expansion into space has changed radically.

(To be continued).


1. Ben R. Finney & Eric M. Jones, eds., Interstellar Migration and the Human Experience, University of California Press, 1985.

2.  John Milton, Paradise Lost, Book 7, lines 621-622.

3.  Konstantin Tsiolkovsky, ‘Dreams of Earth and Sky’, in Tsiolkovsky, The Call of the Cosmos, Foreign Language Publishing House, Moscow, 1960.

4.  Robert Burton, The Anatomy of Melancholy, vols.1-3, Everyman’s Library, J.M. Dent & Sons, 1932  (‘Digression of the Air’ in Vol. 2).

5. Alan Bond, British Interplanetary Society Interstellar Studies Conference, 1979.  A more advanced model of his ‘engineer’s approach’, in terms of genome size, was advanced in ‘On the Improbability of Intelligent Extraterrestrials’, Journal of the British Interplanetary Society 35, 5, 195-207  (May 1982), following his and Anthony R. Martin’s ‘A Conservative Estimate of the Number of Habitable Planets in the Galaxy’, JBIS, 31, 11, 411-415  (November 1978)  and Part 2, JBIS, 33, 3, 101-106  (March 1980).

6. Martyn J. Fogg, ‘Extra-solar Planetary Systems, II – Habitable Planets in the Galaxy’, JBIS, 39, 99-109  (1986).

7.  Martyn J. Fogg, ‘Extra-solar Planetary Systems, III – Potential Sites for the Origin and Evolution of Technical Civilizations’, JBIS, 39, 99-109  (1986).

8. Martyn J. Fogg, ‘Temporal Aspects of the Interaction among First Galactic Civilizations:  the “Interdict Hypothesis”‘, Icarus, 69,  (1987).

9.  A.G.W. Cameron, ed., Interstellar Communication, Benjamin, New York, 1963.

10. G.M. Tovmasyan, ed., Extraterrestrial Civilizations, Academy of Sciences of the Armenian SSR, 1965;  trans. Israeli Programme for Scientific Translations, Jerusalem, 1967.

11. Carl Sagan, ed., Communication with Extraterrestrial Intelligence, MIT Press, 1973.

12. Freeman J. Dyson, ‘Intelligent Life in the Universe’, lecture, Astronomical Society of the Pacific, NASA, and the City College of San Francisco, 18th September 1972.

13.  E.F. Mallowe, ‘Interstellar Communication:  Scientific Perspectives’, JBIS, 28(3), 223-224  (1975).

14. Duncan Lunan, ‘Past Contact and the Moving Caravan’, in Chris Boyce, Extraterrestrial Encounter, David & Charles, 1979.

15. Carl Sagan & I.S. Shklovskii, Intelligent Life in the Universe, Holden-Day, 1966.

16.  Sebastian von Hoerner, ‘The Search for Signals for Other Civilizations’, reprinted in Cameron, ed., Interstellar Communication, op cit.

17. Duncan Lunan, ‘Notes towards a Politics of Survival’, Science & Public Policy, February 1987, translated in Katedra, Yugoslavia, January 1987, trans. in Samo Resnik, ed., Fantazia, Casopis za kritiko znanosti, Llubjana, Yugoslavia, 1990;  ‘Introduction to the Politics of Survival’, ‘The Politics of Survival’, Asgard, March 2002, reprinted as Appendix in Incoming Asteroid!  What could we do about it?, Springer, New York, 2013.

18. Duncan Lunan, Man and the Planets, Ashgrove Press, Bath, 1983.

19. Chris Boyce, ‘Are We Mentally Prepared?’  (guest chapter), in Duncan Lunan, Man and the Stars, Souvenir Press, London, 1974.  (Interstellar Contact in USA, without colour plates, Henry Regnery Co., 1975).

20.  V.A. Hughes, D. Routledge, ‘An Expanding Ring of Interstellar Gas with Centre Close to the Sun’, Astronomical Journal, 77, 210  (1973).

21.  Michael Allaby & James Lovelock, The Great Extinction, Secker & Warburg, 1983.

22.  Victor Clube & Bill Napier, The Cosmic Serpent, Faber, New York, 1982.


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