* Fermi's paradox

Photograph: The majestic Sombrero Galaxy (M104), 28 million light-years from Earth, as seen by the Hubble Space Telescope. A brilliant white core is encircled by thick dust lanes in this spiral galaxy, seen edge-on. The galaxy is 50 000 light-years across. Credit: NASA and The Hubble Heritage Team (Space Telescope Science Institute / Association of Universities for Research in Astronomy). Reproduced under conditions of the Space Telescope Science Institute.

FERMI’S PARADOX: SO IN THE END, IF THE GALAXY IS ALREADY FULLY COLONIZED, WHERE IS EVERYBODY?

Many scientists believe that the number of advanced civilizations in our galaxy could reach millions. However, if so, should not we already have proof of this? Others believe that this lack of evidence is suspicious and may mean that there are no other civilizations. Let’s explore this supreme mystery with the help of science fiction.

One summer day in 1950 Enrico Fermi, Nobel Laureate in Physics, was in the Los Alamos National Laboratory along with other eminences: Edward Teller, Herbert York and Emil Konopinski. They were going for lunch, talking animately and informally about accounts of flying saucers appeared in the media. Fermi reasoned using the scientific method. First, he defined the problem: could there be advanced extraterrestrials, and could they get here?

FERMI’S THEORY

Fermi developed a theory that this is possible, as in Roland Emmerich's film “Independence day”, with Will Smith, Jeff Goldblum and Bill Pullman (Twentieth Century Fox, 1996). But Fermi went on: his experimental hypothesis would be “there is a direct and obvious impact on the history of Humankind”; his null hypothesis would be “there is no direct or obvious impact on the history of Humankind by an alien invasion or colonization”. The experiment would need to study all historical records. There are astronomical records for at least the past 3500 years, but neither recent nor distant history recorded an invasion of Earth by extraterrestrials. So the Earth was never invaded or colonized by extraterrestrials in historical times.

THE PARADOX

The optimists believe that there must be advanced civilizations in the Galaxy and the more time passes the more appear: some put a range of between 1 million and 1000 millions. And even using slow spaceships, not much faster than ours, a single species could have populated entirely our old Galaxy in just 1% of the current age of it. But Earth was never invaded or colonized in historical times. So when Fermi’s party arrived at the restaurant and the four sat at the table, Fermi suddenly summarized the true mystery of the E.T.s, wondering if that is the case, then where is everybody.

Since then, many people tried to find some explanation for this paradox. Here are some, out of the fertile imaginations of Hollywood but yet have the support of scientists. In italic and [box brackets] we provide details of the films.

THEORY NUMBER 2

Extraterrestrials were already here, as in Ron Howard's “Cocoon”, with Don Ameche, Wildford Brimley, Hume Cronyn, Brian Dennehey, Jessica Tandy, Steve Guttenberg and Tahnee Welch (Twentieth Century Fox, 1985) [they were here 12 000 years ago, in Atlantis]. Archaeology, anthropology and folkloristics studied 4500-year old pyramids and cultures that used astronomy in those times, and paleontology studied the extinctions of dominant species such as dinosaurs, but nothing was proven. These sciences still have much to do for centuries.

THEORY NUMBER 3

There are extraterrestrials here, but the governments are hiding them, as in Barry Sonnelfeld's film “Men in black”, with Tommy Lee Jones and Will Smith (Columbia Pictures, 1997). There were even lawsuits against NASA under a law called Freedom of Information Act. There is an UN office in Vienna, which monitors the Outer Space Treaty of 1966, which requires disclosure of all discoveries in space. The International Astronomical Union is not dependent on any government, and its affiliates are free to publication. The International Academy of Astronautics holds a protocol on Search of Extraterrestrial Intelligence which requires sharing information with the public, and the so-called “Flag of the Earth” flies in many observatories as a commitment to all Humankind. The documents and facilities released so far are inadequate, and the conclusion may still take decades. 

THEORY NUMBER 4

Extraterrestrials are very close and trying to make contact, as in Steven Spielberg's masterpiece “Close encounters of the third kind”, starring Richard Dreyfuss (Columbia Pictures, 1977) [where several indications point to a meeting with E.T.s on a plateau]. There have already been serious studies on Anomalous Observational Phenomena, such as the strange lights of Hessdalen, in Norway, and experiments which used luminous signs and even Internet websites to attract E.T.s. All these so far was insufficient and work could continue even for decades.

THEORY NUMBER 5

Extraterrestrial are very close, just not trying to make contact, as in the unique epic of Stanley Kubrick “2001: a space odyssey”, written by Arthur C. Clarke (Metro-Goldwyn-Mayer, 1968) [they were waiting patiently on the Moon]. We mapped the entire Earth with a resolution of 10 meters, the space around it with 1 meter resolution, and the Moon, Venus and Mars with a resolution of 100 meters. But experiments conducted so far were insufficient and can still take centuries.

THEORY NUMBER 6

Extraterrestrial are very close but trying to avoid contact, as in Steven Spielberg's unforgettable classic “E.T.: the extraterrestrial”, with Henry Thomas, Robert MacNaughton, Drew Barrymore, Dee Wallace, Peter Coyote and Erika Eleniak (Universal Pictures, 1982) [they collect botanical specimens but flee from humans]. We have no data of inaccessible places on Earth and other Solar System bodies, and we are expecting an error of theirs and nothing so far. A conclusion is quite impossible, since this hypothesis cannot be tested experimentally.

THEORY NUMBER 7

Extraterrestrial are very close but we just do not realize this, as the Ewoks in the latter part of the original trilogy of George Lucas, directed by Richard Marquand, “Return of the Jedi”, with Mark Hamill, Harrison Ford and Carrie Fisher (Twentieth Century Fox, 1983) [a primitive society does not know that there is an interstellar war and that its new “moon” is actually the gigantic space station, the "Death Star".] Astronomers have used from the Hubble Space Telescope to the Super Kamiokande, which detects neutrinos, to explore the Universe. We have perhaps millions of years of work ahead.

THEORY NUMBER 8

There are extraterrestrials who do not want to come here but still are interested in contact, as in the Robert Zemeckis' film based on a novel by a certain person, “Contact”, starring Jodie Foster (Warner Brothers, 1997) [they send microwave signals when they begin to receive our TV broadcasts]. Since 1960, we have sought with radio telescopes and detectors of laser signals. One of the few projects, SETI@home, uses millions of computers of volunteers, through the Internet, to analyze data from the Arecibo radio telescope, the largest in the world. In 1972 an 1973 space probes Pioneer 10 and 11 were launched carrying plaques identifying, in scientific language, their planet and time. They were followed by Voyager 1 and 2 in 1977, with golden records with images and sound. In 1974 the Arecibo radio telescope sent a powerful message to a star cluster distant 25 000 light-years. A conclusion will still take thousands of years.

THEORY NUMBER 9

There are Extraterrestrials but do not want to come here and get in touch with us, similar to what happens in today's popular culture reference created by the Wachowski Brothers (Andy Wachowski and Lana Wachowski) “The matrix”, with Keanu Reeves, Laurence Fishburne and Carrie-Anne Moss (Warner Brothers, 1999) [the advanced “machines” are not interested in space travel and do not seek electricity above the clouds, with solar panels in orbit, or migrating to the Moon. In fact, agent Smith criticizes humans for expanding voraciously, like a virus]. We have sent space probes to Neptune and infrared telescopes such as IRAS have sought energy sources with artificial features among the stars. It can take millions of years to review all planetary systems. But our efforts in the Solar System were enough, so we are sure we do not share it with other beings of advanced technology.

THEORY NUMBER 10

There are other civilizations in our Galaxy, just do not have advanced technology, as in the film by Jonathan Frakes, using the franchise started by Gene Roddenberry, “Star Trek: Insurrection”, starring "next generation" Patrick Stewart (Paramount Pictures, 1998) [where a society no longer sees benefits to its advanced technology and decides to live as hippies]. It could still take millions of years to have maps of all the planets in the Galaxy. But besides Europa, a natural satellite of Jupiter, and Titan, of Saturn, we can safely announce that in the Solar System there are no non-technological civilizations.

THEORY NUMBER 11

There is only primitive life, if there is extraterrestrial life, as in the planet of the classic of science fiction, with Sigourney Weaver in her best character and directed by James Cameron, “Aliens” (Twentieth Century Fox, 1986) [set in a world plagued by monstrous beasts]. We sent probes with biological instrumentation to the most Earth-like planet, Mars, and it does not have a lush ecosystem that may harbor intelligent beings. It may take millions of years to get data from the rest of the Galaxy. But apart from Europa and Titan, we are confident that "Homo sapiens" is the most advanced biological being of our neighborhood.

Finally, each of these theories could apply to a specific civilization, but the more civilizations exist, the more likely to reach the following theory:

THEORY NUMBER N

There is a least one extraterrestrial civilization that regardless of the excuses of other civilizations is coming to Earth, and sooner or later is going to arrive, as in the second movement, “The Empire strikes back”, of the symphony number one in three movements of George Lucas, this time with Irvine Kershner holding the conductor's baton (Twentieth Century Fox, 1980) [where the rebels hide in an obscure corner of the Galaxy but are eventually discovered by the Empire]. We went in person to the Moon, our robotic probes landed on Titan, Saturn's moon, and we have permanent bases at 400 kilometers altitude in space. The extraterrestrials have not arrived, and we still do not colonize the entire Galaxy. It may be that the waiting time has been insufficient, and obviously our own efforts to colonize the Galaxy were also insufficient. For a solution to Fermi’s paradox and to confirm definitely whether or not we are alone in the Galaxy, perhaps it will take up to 100 million years.

A. L.

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Based on a lecture given at USP, on 3 April 2004. First published in ABC Color, on 18 June 2006. A slightly retouched version of this article, joined to many other related articles from this website making a compilation titled "Do you believe in UFOs?", is available for sale in electronic book format at http://www.amazon.com/dp/B00GF0REFI. Photograph: The majestic Sombrero Galaxy (M104), 28 million light-years from Earth, as seen by the Hubble Space Telescope. A brilliant white core is encircled by thick dust lanes in this spiral galaxy, seen edge-on. The galaxy is 50 000 light-years across. Credit: NASA and The Hubble Heritage Team (Space Telescope Science Institute / Association of Universities for Research in Astronomy). Reproduced under conditions of the Space Telescope Science Institute.

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