Final publication appeared in , March 2015, 15(3):195-199. Final publication is available from Mary Ann Liebert, Inc., publishers http://dx.doi.org/10.1089/ast.2014.1247

The is Neither Fermi’s Nor a Paradox

Robert H. Gray

Abstract

The so-called Fermi paradox claims that if technological life existed anywhere else, we would see evidence of its visits to —and since we do not, such life does not exist, or some special explanation is needed. , however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked “where is everybody?”—apparently suggesting that we don’t see extraterrestrials on Earth because may not be feasible, but not suggesting that intelligent does not exist, or suggesting its absence is paradoxical. The claim “they are not here; therefore they do not exist” was first published by Michael Hart, claiming that interstellar travel and colonization of the galaxy would be inevitable if intelligent extraterrestrial life existed, and taking its absence here as proof that it does not exist anywhere. The Fermi paradox appears to originate in Hart’s argument, not Fermi’s question. Clarifying the origin of these ideas is important, because the Fermi paradox is seen by some as an authoritative objection to searching for evidence of extraterrestrial —cited in the U. S. Congress as a reason for killing NASA’s SETI program on one occasion—but evidence indicates that it misrepresents Fermi’s views, misappropriates his authority, deprives the actual authors of credit, and is not a valid paradox.

Keywords: Astrobiology, SETI, Fermi paradox, extraterrestrial life

1. Introduction later. If Fermi was skeptical about interstellar travel, then using his name for an argument that requires it is The so-called Fermi paradox is often cited in misleading. discussions about the search for extraterrestrial This paper will show that the phrase “Fermi intelligence (SETI), and has generated a sizable paradox” first appeared in 1977, 27 years after Fermi’s literature (Brin, 1983; Webb, 2011). One typical question in 1950, and in connection with Michael definition is (Horowitz, 2002): Hart’s 1975 argument “they are not here; therefore they If technologically advanced have do not exist,” which was extended by Frank Tipler in inhabited our Galaxy for timescales of 1980. The Fermi paradox appears to confuse Fermi’s approximately a billion years, and if some of these question with the Hart-Tipler argument— have engaged in interstellar travel and colonization, misrepresenting Fermi’s views and obscuring the then why have we not seen physical evidence of identity of the actual authors. their visits? The Fermi paradox caused a crisis in SETI beginning around 1975 (Dick, 1998): This implies that Enrico Fermi, a great physicist, was skeptical about the possible existence of This crisis undermined the very foundation of technologically advanced extraterrestrial life and the SETI endeavor, bringing into question the viewed the absence of visits as a paradox, but the logic of the radio search paradigm by claiming available evidence shows that this was not his view. that all searches of the electromagnetic spectrum Fermi apparently never published a word on the might well be fruitless. subject of extraterrestrial life or interstellar travel. He Senator William Proxmire (D-WI) cited Tipler’s name is known to have asked “where is everybody?” at a when he killed NASA’s SETI program in 1981 for the lunch in 1950, questioning the plausibility of interstellar following year (Proxmire, 1981) using language very travel according to eye-witness accounts presented much like the Fermi paradox:

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... if intelligent beings did exist elsewhere and 3. Origin of Fermi’s Question possessed the technology for interstellar communication they would have developed Fermi is known to have asked “where is interstellar travel and thus would already be everybody?” during a lunch at Los Alamos in 1950 present in our . (Jones, 1985; Finney & Jones, 1985). Fermi’s question is often taken as challenging the idea that technological NASA’s SETI program was restarted but canceled extraterrestrial life exists because we see no evidence of a second time in 1993 (Garber, 2014) by Senator visits, but accounts from people who were present make Richard Bryan (D-NV), and since then no U. S. it clear that Fermi was questioning the feasibility of government funds have been appropriated for searches. interstellar travel and not questioning the possible This purported paradox attributed to Fermi existence of technological extraterrestrial life. continues to have influence today, generating academic Eric Jones solicited letters in 1984 from the three discussion and possibly contributing to a de facto surviving people present at the lunch—Emil prohibition on government support for research in a Konopinski, , and Herbert York (Fermi branch of astrobiology, but it is clearly not Fermi’s and died in 1954)—asking them about the occasion. does not constitute a valid paradox. Excerpts from the responses show that the conversation

focused on interstellar travel and its feasibility: 2. Origin of the phrase Fermi Paradox Konopinski: The phrase ‘Fermi paradox’ seems to have first appeared in print in March of 1977, referring to Fermi’s When I joined the party I found being discussed question “where is everybody?” (Stephenson, 1977): evidence about flying saucers. That immediately brought to my mind a cartoon I had recently seen The first and simplest answer to ‘Fermi’s in the New Yorker, explaining why public trash paradox’ has been put forward by Hart ... cans were disappearing from the streets of New mankind is the first intelligent species within this York City. ... The cartoon showed what was Galaxy, and that consequently there could have evidently a flying saucer sitting in the been no visitations to this Solar System by other background and, streaming toward it, “little civilizations. green men” (endowed with antennas) carrying Stephenson believes that he coined the term for trash cans. ... There ensued a discussion as to publication (Stephenson, 2014): whether the saucers could somehow exceed the . At the time the word paradox was used in conversation to describe the problems facing Teller: SETI researchers and 's story about I do not believe that much came from this Fermi and "Where is everybody" was often conversation, except perhaps a statement that the mentioned. I put single quotes around 'Fermi's distances to the next location of living beings Paradox' ... as an apology for using a short may be very great and that, indeed, as far as our convenient two word label for a large and galaxy is concerned, we are living somewhere in indistinct field of conjecture. the sticks, far removed from the metropolitan The Fermi paradox appeared as the subject of a area of the galactic center. conference session in April, 1977 (Martin, et al. , 1979), York (about Fermi): and the phrase began appearing frequently in the early 1980s—cited in 19 places in one SETI symposium ... he went on to conclude that the reason that we (Papagiannis, 1984)—and it appears frequently today, hadn’t been visited might be that interstellar five places in one recent book (Vakoch, 2014). The flight is impossible, or, if it is possible, always phrase was not found in any publication earlier than judged to be not worth the effort, or Stephenson’s paper, and was not found in any title in a technological doesn’t last long SETI bibliography with 1,488 references through enough for it to happen. February 1977 (Mallove, 1978). York clearly recalled Fermi as questioning the It is surprising that the phrase did not appear in feasibility of interstellar travel, Teller seems to have print until 1977—27 years after Fermi’s question in thought that distance (and by implication, difficulty of 1950, but only two years after Hart’s 1975 paper—and interstellar travel) was the reason for not seeing in connection with Hart’s name, suggesting that the extraterrestrials, and Konopinski did not address the Fermi paradox is more closely related to Hart’s topic, although he places the event in time, because argument than Fermi’s question. such a cartoon appeared May 20, 1950. None of the

2 respondents reported that Fermi questioned the possible achieved space travel, and would have explored existence of extraterrestrials, or suggested that not and colonized the Galaxy, as we have explored seeing any was a paradox—yet those ideas are the core and colonized the Earth. However... they are not of the Fermi paradox. here; therefore they do not exist. Fermi’s question was recalled by Konopinski as Hart argued that all other possible explanations for “But where is everybody?”, by Teller as “Where is the absence of extraterrestrials on Earth are false, everybody?”, and by York as “Don’t you wonder where grouping them into four categories: (1) “physical everybody is?”, which suggests “where is everybody?” explanations,” for example, interstellar travel is as Fermi’s likely wording, although respondents may infeasible, (2) “sociological explanations,” for example, have been influenced by Jones’ use of that phrase. The extraterrestrials have chosen not to visit Earth, (3) wording has been given by others who were not present “temporal explanations,” for example, they have not as “where are they?” (Sagan, 1963; Sagan & Shklovski, had time to reach the Earth, and (4) the Earth has been 1966; Oliver & Billingham, 1971; Drake & Sobel, visited, but we do not observe them here at present. He 1992), and some give the time as during WWII, but the rejected all four possible explanations and concluded eyewitness accounts seem most authoritative. that only his explanation is correct—they do not exist Fermi’s question seems to have first appeared in anywhere in the Galaxy, a matter of ~10 11 —and print in a footnote to a discussion of the possibility that offered a corollary policy conclusion “an extensive with an extraterrestrial civilization occurred search for radio messages from other civilizations is within historical times (Sagan, 1963): probably a waste of time and money.” This possibility has been seriously raised before; David Viewing published a somewhat similar for example, by Enrico Fermi, on a now rather argument assuming interstellar travel and colonization well-known dinner table discussion at Los (Viewing, 1975), but unlike Hart, he concluded that Alamos during the Second World War, where he extraterrestrials might exist and that we should search introduced the problem with the words “Where for interstellar probes as well as search for signals. are they?” Frank Tipler extended Hart’s ideas, suggesting smart machines rather than biological colonists (Tipler, The context suggests that Sagan thought Fermi’s 1980): point was that if extraterrestrials had visited the Earth recently, we should see evidence of it, and since we ... a self-replicating universal constructor with don’t, they have not visited recently. Another early intelligence comparable to the level ... mention of Fermi’s question appeared in the Project such a machine combined with present-day Cyclops report (Oliver & Billingham, 1971), apparently rocket technology would make it possible to challenging the feasibility of interstellar travel: explore and/or colonize the Galaxy in less than 300 million years... If, on the other hand, interstellar travel is much easier than we predict, we would argue that to This was a major extension of Hart’s ideas, maintain radio silence is no real protection, for in because Hart mentioned “robots” in only one sentence, this case a galactic survey would not need to as potentially manning spaceships on long voyages depend on beacons. The question to be answered carrying frozen zygotes. Tipler’s mechanism would in this case is Enrico Fermi’s Where are they? presumably operate for hundreds of millions of years, follow orders without question or deviation or The so-called Fermi paradox clearly misrepresents , explore or colonize billions of and Fermi’s views, by using his name for an argument that perhaps even moons and at no extra cost, assumes interstellar travel (which he was questioning), operate in places where life could not survive, and solve and because it challenges the possible existence of a multitude of other problems. technological extraterrestrial life (which he was not Tipler’s conclusion was even more sweeping than questioning). It might be more accurate to describe Hart’s—that Man is probably the only intelligent “where is everybody?” as Fermi’s question about the species in the Universe (Tipler, 1981), not just our feasibility of interstellar travel . Galaxy—a matter of ~10 11 more stars. That universal

result seems strikingly similar to the result of the 4. The Hart-Tipler Argument Genesis story which describes the creation of only one Michael Hart appears to have been the first to intelligent species (Leeming, 2010), and it is surprising publish the argument “they are not here; therefore they that Tipler did not comment on this similarity, because do not exist” (Hart, 1975): elsewhere he explained biblical stories such as miracles using physics (Tipler, 2007). If ... there were intelligent beings elsewhere in our Galaxy, then they would eventually have

3 Hart and Tipler’s arguments have been challenged argument that leads to a contradiction, and the on grounds such as the energy required for interstellar contradiction suggests that something is wrong. travel (Oliver, 1994) and risks of self-replicating The Hart-Tipler argument takes the seemingly machines and rates of colonization (Sagan & Newman obvious fact they are not here as evidence that a 1983). Others have taken their arguments as serious premise “technological extraterrestrials exist” must be objections to the idea that technological extraterrestrial false, because if they did exist, their colonization life might exist elsewhere (Proxmire, 1981, Zuckerman argument leads to the conclusion they are here , which & Hart 1982, Papagiannis, 1985). seems absurd. This is a reductio ad absurdum The Hart-Tipler argument is very similar to the argument, not a paradox, although like a paradox it Fermi paradox, although there is a slight difference. depends on every statement being true—yet the The Fermi paradox is often posed as a question about argument consists of many speculations which are not why we don’t see extraterrestrials, using Hart’s known to be true. For example, “colonizing the argument that we should, but as a question it permits galaxy” tacitly assumes: (1) interstellar travel is answers other than “they do not exist”—although it feasible, (2) the Galaxy would be filled quickly, (3) the begs that answer. Earth would be among ~10 11 or more colonized worlds, (4) this entirely colonized state would persist for many 5. Proper Attribution millions or billions of years. Any or all of those might be false, so a Hart-Tipler argument or a Fermi paradox Using Fermi’s name for the so-called Fermi making those assumptions can not be valid. Two paradox is clearly mistaken, because (1) it hundred years ago, they are not here could have been misrepresents Fermi’s views, which were skeptical said about dinosaurs, although a great deal of evidence about interstellar travel, but not about the possible has been found since then. The claim of paradox has existence of extraterrestrials, and (2) its central idea been rejected before (Freitas, 1983). “they are not here; therefore they do not exist” was first A variation on the Hart-Tipler argument is they do published by Hart. Priority of publication and accuracy not exist because we have not received their signals suggests using a name like Hart-Tipler argument (Wesson, 1990; Wikipedia, 2014). This tacitly assumes instead of “Fermi paradox.” that a complete search for signals has been performed, A name change has been suggested before. which is not true. The literature on searches (Tarter, Charles Seeger suggested “... ‘Fermi Paradox’ is an 1995) indicates that only a small fraction of the radio unfortunate and thoroughly misleading appellation.” spectrum has been searched—0.3 GHz in surveys (Seeger, 1985). reportedly urged “... covering much of the sky (Leigh & Horowitz, 2000) we must call it the ‘Hart Paradox,’ rather than the using transit observations, and 2 GHz in targeted ‘Fermi Paradox’ ...” (Papagiannis, 1985). The phrase searches of 800 stars (Backus, et al ., 2004)—out of a “Fermi-Hart paradox” has been used in some papers terrestrial microwave window from 1-10 GHz, a free- (Wesson, 1990). Stephen Webb suggested space window up to 60 GHz (Oliver & Billingham, “Tsiolkovsky-Fermi-Viewing-Hart paradox” (Webb, 1971), and much more electromagnetic spectrum 2002). beyond including optical. Few searches would have Konstantin Tsiolkovsky is said to have recognized detected low-duty-cycle signals anticipated by some similar issues in the 1930s. He believed that space (Benford, 2008; Gray, 2011), because both radio and travel was possible, and also believed that life must optical surveys typically observe positions for only exist on planets around many other stars, and he noticed minutes. An incomplete search for signals can not be potential contradictions (Lytkin, et al ., 1995): used as evidence of complete absence of technological (1) if these beings exist they would have visited earth extraterrestrials. (2) if they exist they would have given us some sign of their existence 7. Conclusions

He resolved the contradiction with the idea that “it The so-called Fermi paradox misrepresents Fermi’s is not yet time” for them to visit us, and that “our means views about the feasibility of interstellar travel and the are too weak to perceive these signs.” Lytkin et al . possible existence of intelligent extraterrestrial life, suggested that the “Fermi Paradox” would more uses his name and authority for ideas originated by Hart properly be known as the “Fermi Question” and did not and Tipler, and asserts a logical paradox where none suggest adding Tsiolkovsky’s name. exists, so it is difficult to see any valid use for the phrase. It’s not Fermi’s idea, and it’s not a paradox. 6. No Paradox Fermi asked “where is everybody?”, questioning

The word paradox is usually taken to mean a self- the feasibility of interstellar travel, but not questioning contradictory statement, or a seemingly logical the possible existence of intelligent extraterrestrial life,

4 so it seems clear that Fermi’s name should not be used Freitas, R. A. (1983) There is No Fermi Paradox, JBIS for a so-called Fermi paradox which depends on 62:518-520. interstellar travel, and which does question the Finney, B. R. and Jones, E. M. (1985) Is Anybody Home? Introduction; Synopsis of Fermi’s Question, in Interstellar existence of extraterrestrials—the opposite of his views. Migration and the Human Experience , Finney B. R. and Jones Fermi’s question might more accurately be called E. M. (eds.), University of California Press, pp 298-300. Fermi’s question about the feasibility of interstellar Garber, S. J. (2014) A Political History of NASA’s SETI travel, to avoid mistaking it as an argument against the Program, in Archaeology, Anthropology, and Interstellar possible existence of intelligent extraterrestrial life. Communication , Vakoch, D. A. (ed.), NASA SP-2013- The argument “they are not here; therefore they do 4412, pp 23-48. not exist ” was first published by Hart and extended by Gray, R. H. (2011) The Elusive Wow: Searching for Tipler, and might be called the Hart-Tipler argument Extraterrestrial Intelligence , pp 128-129, Palmer Square Press, Chicago. against the existence of technological extraterrestrials. Hart, M. H. (1975) An Explanation for the Absence of This is not exactly the same as the Fermi paradox, but it Extraterrestrials on Earth, Q. Jl R. astr. Soc. 16:128-135. is the simplest answer to the question “where is Horowitz, P. (2002) The Fermi Paradox, in SETI 2020 , SETI everybody?” if interstellar travel and colonization are Institute, Mountain View, pp 373. Also at: assumed. It seems misleading to cloak the Hart-Tipler http://frank.harvard.edu/~paulh/unpublished/fermi.htm . argument with Fermi’s name and authority, because Jones, E. M. (1985) “Where Is Everybody?” An Account of doing so deprives the true authors of credit and Fermi’s Question, LA-10311-MS, UC-34b, CIC-14 Report attributes views to Fermi which he did not hold. Collection, March 1985. Some people may feel that the so-called Fermi http://www.fas.org/sgp/othergov/doe/lanl/la-10311-ms.pdf retrieved March 7, 2014. Also Physics Today 38 Aug. paradox is a sleeping dog that should be left to lie, 1985, pp 11-13, without full correspondence. because it is established in the scientific literature and Leigh, D. and Horowitz, P. (2000) Strategies, Implementation public mind, but most people would agree that clearly and Results of BETA, in Bioastronomy 99: A New Era in mistaken and misleading terminology should be the Search for Life in the Universe , ASP Conference Series corrected. The issue is important, because the Hart- Vol. 213, Lemarchand, G. and Meech, K. (eds.). Tipler argument was cited as a reason for killing Lytkin, V., Finney, B., and Alepko, L. (1995) Tsiolkovsky, NASA’s SETI program on one occasion in the U. S. Russian Cosmism and Extraterrestrial Intelligence, Q. Jl R. Congress, and under the guise of Fermi’s name and the astr. Soc. 36:373. claim of a logical paradox, it may continue to inhibit Mallove, E. F., Connors, M. M., Forward, R. L., and Paprotny, Z . (1978) A Bibliography on the Search for funding and research in that area of astrobiology. Extraterrestrial Intelligence , NASA-RP-1021. Martin, A. R. (1979) The Fermi Paradox: A Forum for Acknowledgements Discussion, Martin, A. R. (ed.), JBIS 32:424-434.

The author is grateful to Amir R. Alexander, Oliver, B. M., and Billingham, J. (1971) : A Design Study for a System for Detecting Extraterrestrial Steven J. Dick, Steven D. Lord, and Michael A. Warner Life , NASA CR 114445, p 31. for comments on drafts of this paper, and grateful to Oliver, B. M. (1994) Galactic Colonization and Other Flights Eric M. Jones, David G. Stephenson, and Stephen of Fancy, IEEE Potentials , Aug.-Sept. 1994, pp 51-54. Webb for helpful information. Tarter, J. (1995) Summary of SETI Observing Programs, SETI Institute, and updates such as History of SETI Author Disclosure Statement Searches, http://setiquest.org/wiki/index.php/Seti_programs retrieved March 18, 2014. No competing financial interests exist. Tipler, F. J. (1980) Extraterrestrial Intelligent Beings do not Exist, Q. Jl R. astr. Soc. 21:267-281. References Tipler, F. J. (1981) Additional Remarks on Extraterrestrial Intelligence, Q. Jl R. astr. Soc. 22:279-292. Backus P. R. and the Project Team (2004) Project Tipler, F. J. (2007) The Physics of Christianity , Doubleday, Phoenix: A Summary of SETI Observations and Results, New York. 1995-2004, Bull. AAS, 36:805. Papagiannis, M. D. (1985) The Search for Extraterrestrial Benford, G., Benford, J., Benford, D. (2008) Searching for Cost Life: Recent Developments , Papagiannis, M. D. (ed.), p Optimized Interstellar Beacons, Astrobiology 10:491-498. 437, Reidel. Brin, G. D. (1983) The Great Silence: the Controversy Proxmire E. W. (1981) Congressional Record 127:14, (July Concerning Extraterrestrial Intelligent Life, Q. Jl R. astr. 30, 1981), p S18635. Soc. 24:283-309. Sagan, C. (1963) Direct Contact Among Galactic Dick, S. J. (1998) Life on Other Worlds: the 20 th -Century Civilizations by Relativistic Interstellar Flight, . Extraterrestrial Life Debate , Cambridge, pp 218. Space Sci. 11:485-498, p 495. Drake, F. D. and Sobel, D. (1992) Is Anyone Out There?— Sagan, C., and Newman, W. I. (1983) The Solipsist Approach to The Scientific Search for Extraterrestrial Intelligence , pp Extraterrestrial Intelligence, Q. Jl R. astr. Soc. 24:113-121. 130-131, Delacorte Press, New York.

5 Sagan, C., and Shklovski, I. S. (1966) Intelligent Life in the Universe, Holden-Day, San Francisco, p 448. Seeger, C. L. (1985) Fermi Question, Fermi Paradox: One Hit, One Out, in The Search for Extraterrestrial Life: Recent Developments , Papagiannis, M. D. (ed.), Reidel, p 491. Stephenson, D. G. (1977) Factors Limiting the Interaction Between Twentieth Century Man and Interstellar Cultures, JBIS 30, No. 3:105-108. Stephenson, D. G. (2014) Private communication with Robert Gray, April 2, 2014. Viewing, D. (1975) Directly Interacting Extraterrestrial Technological Communities, JBIS 28:735-744. Vakoch, D. A. (2014) Archaeology, Anthropology, and Interstellar Communication , Vakoch, D. A. (ed.), NASA SP-2013-4412. Webb, S. (2002) If the Universe Is Teeming with Aliens...Where Is Everybody? Fifty Solutions to Fermi’s Paradox and the Problem of Extraterrestrial Life , Springer. Webb, S. (2011) Pondering the Fermi Paradox, in Searching for Extraterrestrial Intelligence: Past, Present, and Future , Shuch, H. P. (ed.), Springer. Wesson, P. S. (1990) Cosmology, Extraterrestrial Intelligence, and a Resolution of the Fermi-Hart Paradox, Q. Jl R. astr. Soc. 31:161-170. Wikipedia (2014) Fermi Paradox, retrieved February 16, 2014, http://en.wikipedia.org/wiki/Fermi_Paradox . Zuckerman, B. and Hart, M. H. (1982) Extraterrestrials: Where Are They? , Pergamon Press.

Address correspondence to: Robert H. Gray Gray Consulting Chicago, Illinois E-mail: [email protected]

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