SETI: A Critical History
Part I Constructing SETI
Chapter 2. SETI Science
There was not a great deal of profound thought
or anything involved in putting it together.
– Frank Drake
When it was first suggested in the late 1950s that the still-new technology
of radio astronomy could be used
to communicate with ETIs, a number of scientists excitedly turned to their
radio telescopes to begin searching for
incoming messages. The National Academy of Sciences saw NASA as a potential
institutional home for a SETI project and invited a group of interested
scientists, including most of those who went on to spearhead America's SETI
effort, to demonstrate that a SETI-style search was plausible. Using a simple
decision model and bold assumptions, SETI's architects did so and then claimed
that they were establishing the ETI discourse on a rigorously experimental
basis for the first time.
Neither Cocconi nor Morrison
was an astronomer. According to historian Steven Dick, they "stumbled onto
the subject of interstellar communication as an aside to their primary research."2
One night some years before they published their famous SETI paper, the
pioneer radio astronomer Frank Drake was
conducting observations for his doctoral dissertation when he found a radio
signal that appeared to be anomalously coherent. The fact that the signal
had a pattern suggested to Drake that it might be of intelligent origin.
It initially looked to be coming from a distant galaxy. This got Drake thinking,
too, about the possibility of using radio waves to communicate across interstellar
|Fig. 1. Frank Drake4
Drake was not the first in his profession to be tempted by objects that
appeared to be the product of intelligence to speculate about the existence
of ETIs. In the early modern period Johannes Kepler
was one of the first astronomers to turn an optical telescope onto the Moon.
When he did so he concluded that the objects we today call craters were
so "perfectly round" that they had to be of intelligent origin. (He thought
they might be forts.5) Then, around the turn of the 20th century
Percival Lowell was inspired by Giovanni
Schiaparelli's intimations that the
long, straight lines he observed on Mars were the product of intelligence
to speculate extensively about what Martians might be like.6
The signal Drake found turned out to be of terrestrial origin. But when
Drake got a job at one of America's first big radio astronomy facilities,
the National Radio Astronomy Observatory (NRAO) in Green
Bank, West Virginia, he convinced his boss to allow him to test his
idea that radio waves might be conveying
messages to Earth. When Cocconi and Morrison's paper was published, Drake
was already quietly preparing to run the very kind of search the two recommended.
As Drake later put it, "Morrison and Cocconi were thinking and we were building."7
From this first moment in SETI's history a subtle rivalry between reflection
and action was established that reappeared regularly.
During the spring of 1960 Drake searched for messages from two nearby stars.
He found none.
The first SETI conference was held the year after Drake's search, at the
same site. It was convened by the Space Science Board of the NAS. J. P.
T. Pearman from the Space Science Board published a summary of the meeting,
"Extraterrestrial Intelligent Life and Interstellar Communication: An Informal
Discussion."8 As the title reveals, the scientists who convened
this conference considered it "informal." Proceedings of the meeting were
never formally published; Pearman’s seven-page article is the most extensive
record of the SETI project's genesis.
The NAS has, on two occasions, played a pivotal role in determining SETI's
institutional status within American science. Convening this week-long conference
at Green Bank, held soon after the possibility of a SETI-style search was
suggested, was the first. The purpose of the meeting was to investigate
whether SETI could be considered part of NASA's existing mission to search
for extraterrestrial life.9 The ideas that the proper
institutional home for SETI was NASA, where it would be part of the broader
SETL effort, both had important consequences for SETI.
Cocconi and Morrison's paper and Drake's search had been catalysts around
which an informal group of American-based scientists known to be interested
in SETI had begun to take shape. The Green Bank meeting attracted many of
them, including four who became key SETI figures: Morrison, Drake, Carl
Sagan, and Bernard Oliver.
Sagan was, at the time, a young astronomer whose interest in the possibility
of ETIs had been kindled by several college and graduate-school mentors.
Oliver was an electrical engineer and an early Silicon Valley entrepreneur.
As the head of Research and Development at Hewlett Packard, he was responsible
for the team that developed the hand-held calculator. He had heard about
the Green Bank meeting and asked Drake if he could attend. Drake, who hosted
the meeting, had no funding to fly Oliver in, so Oliver hitched a ride with
a private pilot. It was not the last time Oliver made a resourceful and
somewhat spectacular appearance in SETI's history.
|Fig. 2. Phillip Morrison10
The men who attended this conference were invited because they were already
excited about SETI. They did not spend their time together thinking critically
about whether a SETI-style search represented a good way to confirm the
existence of ETIs; they wanted to develop a rationale to justify additional
searches. And they believed the key to that was having a plausible rationale
for why ETIs exist.
When Cocconi and Morrison wrote their paper about how distant beings might
try to communicate with us, they began by acknowledging that reliable theories
about planet formation, the origin of
life, and the evolution of advanced scientific societies did not yet exist.
The authors believed that without these it was impossible to make reliable
estimates of the probability that ETIs exist.11 This did not,
however, deter Drake, who set the agenda for the Green Bank meeting. He
took the three variables Cocconi and Morrison identified and expanded them
into seven. He then used them to frame the Green Bank discussions about
the likelihood that ETIs existed. These seven variables subsequently became
part of what is now known as the Drake Equation.
According to the Drake Equation, the number of civilizations that might
be sending us messages was the product of the rate of star
formation, the percentage of stars that form planets, the percentage
of those hospitable to life, the percentage of those on which life actually
emerges, the percentage of those on which life evolves to become intelligent
life, the percentage of those capable of interstellar communication, and
the longevity of such civilizations. It is often written as follows:
N = R* fp ne fl fi
Despite its central importance to SETI, the Drake Equation was not the product
of studied reflection. As Drake recalled, "I thought we should organize
the meeting, and that caused me simply to think about what we needed to
discuss – there was not a great deal of profound thought or anything
involved in putting it together."12 Even more striking than the
casualness with which Drake constructed his equation was the boldness of
the conferees' probability estimates for each of its seven variables.
The attendees felt they were being conservative in estimating that the rate
of star formation in our galaxy, R*, was about one per year. They
acknowledged the uncertainty around their estimate of the percentage of
stars that form planets, fp, but settled on 40%. For
each star that forms planets, they settled on an estimate that between one
and five of them would have environments suitable to life; this was based
on "pure guesswork." Nor did the participants seem to struggle much when
they concluded that the probability of life actually arising on such planets,
fl, was "unity," or a certainty, probably because they
could point to expert opinion to support their ambitious assumption.13
According to his biographers, one of the epiphanous moments in Sagan's intellectual
development occurred when a University of Chicago mentor, Harold Urey,
suggested that Sagan attend a colloquium given by Stanley Miller
in 1953. There Sagan learned first-hand about the famous Miller-Urey
experiment in which some of the building blocks of organic life, amino
acids, were synthesized from conditions that were thought to prevail
in the Earth's primordial biosphere. To Sagan the fact that the origins
of terrestrial life could be replicated in a lab meant that life was something
less miraculous and more commonplace than had been previously thought.14
Drake had a similar reaction to the Miller-Urey experiment. As early as
1960 he was discussing how Miller's "molecules, which are the basic building
blocks of life, should provide for its emergence on other planets just as
they apparently did on earth."15 Sagan and Drake were astronomers,
and might have been inclined to latch onto evidence that suggested life
arose elsewhere. However, they were hardly alone in reaching their conclusion.
The chemist Robert Shapiro reported that, "The Miller-Urey experiment is
now recognized as the single most significant step in convincing many scientists
that life is likely to be abundant in the cosmos."16 In the same
year the Green Bank attendees met, the Soviet biochemist Aleksandr I. Oparin,
a co-founder of the theory that the Urey-Miller experiment was designed
to test, claimed that "life ... results each time the requisite conditions
for it are on hand anywhere in the Universe."17 Melvin Calvin,
a Nobel laureate biochemist who was right there at the Green Bank meeting,
argued "that the origin of life was a common and even inevitable step in
Thus, after considering the first four of the Drake Equation's seven variables,
the conferees were inclined to attribute a relatively high probability to
the proposition that ETIs existed. Their deliberations around the probability
to assign to fi, the likelihood that intelligence would
evolve once life originated, were less straightforward. They noted that,
"The successful persistence of a multitude of simpler organisms from ancient
times argues that intelligence may confer no unique benefits for survival
in an environment similar to that of earth."19 They reasoned,
however, that two other factors combined to suggest that intelligence was
likely. First, although the Green Bank conferees did not cite it by name,
the principle of convergence became
an important part of SETI-Science because it established that any given
adaptation could be repeated. Specifically,
convergence suggested that intelligence did not have to be unique to humans.20
In the same way that Calvin served as an "expert witness" at the conference,
establishing that life would inevitably arise on earthlike planets, another
guest had been invited to establish that the convergence of intelligence
had occurred on Earth and was thus likely to evolve elsewhere, too. In the
1960s John C. Lilly was the leading proponent
of the idea that dolphins were intelligent (see dolphins
as a form of alien intelligence).21 When recounting the proceedings
of the conference, the NAS's Pearman reported that Lilly presented "evidence
for the existence of a remarkable level of intelligence among the Cetacea"
and that this evidence was "noted with great interest."22 As
one of Sagan's biographers observed, "If Lilly was right, then the emergence
of intelligence might be more common, less context-specific, than was generally
assumed."23 In other words, if intelligence was found to have
evolved more than once on a single planet, that would be a powerful argument
in favor of its evolving elsewhere, too. Convergence became a key component
of SETI-Science, and the idea quickly circulated. For example, the biologist
Robert Bieri, writing in American Scientist shortly after the Green
Bank meeting, used convergence to discuss the possibility of "Humanoids
on Other Planets."
The phenomenon of convergent
evolution ... shows that, again and again, animals and plants have independently
evolved not only similar structures but also similar biochemical systems
and similar behavioral patterns as solutions to the same fundamental problems....
If we ever succeed in communicating with conceptual beings in outer space
... in all probability they will look an awful lot like us.24
Convergence suggested that the evolution of intelligence elsewhere was possible.
The conferees also discussed why it was probable. We know little
about this aspect of their discussions beyond the conclusion they reached.
The conferees reasoned that the fact that the human species had increased
in both absolute numbers and geographic dispersion was evidence that "intelligence
has definite survival value."25
The Green Bank group felt it was in a position to estimate the probability
of fi by taking account of the facts that intelligence
had apparently evolved at least twice on this planet alone and that the
human species seemed to be thriving. Pearman reported that "Taking these
factors into account and again with some appeal to the unexceptional nature
of the sun and, by extension, the solar system, a value of about unity was
postulated for fi."26
This was an extraordinary conclusion. The conferees had just decided that
it was likely that intelligent life would evolve on planets with an environment
similar to Earth's, and that there were hundreds of millions of these kinds
of environments in the galaxy. They did so with no established theories
to support their assumptions, a risk one of their own number, Morrison,
warned against in the first sentence of his seminal SETI paper.
Two variables of the Drake Equation still remained to be addressed. The
conferees assumed that 20% of intelligent species would develop the capacity
to send radio messages. This was essentially a pure guess: they acknowledged
that this assumption was "vulnerable" and "frankly anthropocentric."27
When the conferees turned to the last variable, L, or the longevity
of a communicative civilization, the imprint of the Cold War was unmistakable.
(See lifetime of extraterrestrial civilizations).
Pearman reported that the participants believed "fears that the value of
L on earth may be quite short are not groundless. However, there
is a least the possibility that a resolution of national conflicts would
open the way for the continued development of civilization for periods of
time commensurate with stellar lifetimes." They concluded that L
was the most influential of all the variables. In the end the conferees
chose two values for L: less than one thousand years and more than
one hundred million years. They obviously considered the resolution of nuclear
conflicts to be a gating factor for a species, the successful negotiation
of which could lead to something like immortality for a civilization.
Multiplying out the probabilities that the conferees assigned to each variable
of the Drake Equation thus produced two estimates of the possibility that
there were ETIs sending us messages. If species were doomed to annihilate
themselves once they evolved the technology to do so (see hazards
to extraterrestrial civilizations), there were "perhaps much less than
103 for the whole galaxy." If, on the other hand, the "more optimistic
values of communicative lifetime" were chosen, there might be between one
hundred thousand and a billion in our galaxy.28
By making this series of optimistic assumptions the Green Bank conferees
were able to demonstrate to the satisfaction of the NAS that the idea that
ETIs exist that might be sending us messages we could understand was, at
the very least, a reasonable one. Although years would pass before NASA
could begin to implement its SETI project, the Green Bank conference established
that a SETI-style search was a plausible part of NASA's mission to search
for extraterrestrial life.
Intelligent Life in the
After reading Cocconi and Morrison's paper, Iosef S. Shklovskii,
the "father" of the Soviet Union's CETI project, wrote, "We may consider
that there are in the galaxy at least a billion planets, rotating around
dwarf stars similar to our sun ... on which a highly organized and possibly
intelligent life may take place."29 A year later Shklovskii was
asked to contribute an article to an anthology commemorating the fifth anniversary
of the 1957 flight of Sputnik. He wrote
about the possibility that ETIs existed and how radio astronomy might be
used to communicate with them. He then elaborated this into a book that
was published in 1963.
Shortly thereafter Sagan wrote to Shklovskii asking that he be allowed to
arrange for Shklovskii's book to be translated and published in the United
States.30 Shklovskii agreed. He also invited Sagan, "a young
and little known planetary astronomer" at the time, to edit the text where
Sagan thought it appropriate to do so, in recognition of Sagan's superior
background in biology.31 In 1966 Sagan published Intelligent
Life in the Universe. It went through four re-printings, suggesting
that the text was the way many Americans were introduced to SETI.
At Green Bank the core of SETI-Science had been constructed around four
ideas: life will inevitably originate on Earth-like planets; nature repeats
useful adaptations, the evidence of which we call the principle of convergence;
intelligence is such a highly useful adaptation that it will inevitably
evolve once life arises; and that radio astronomy is a logical way to communicate
with these intelligences. Sagan edited Shklovskii's original text in such
a way that Intelligent Life in the Universe became an elaboration
of these four core ideas. Sagan also added a fifth that he believed was
needed to complete SETI's conceptual foundation: uniformitarianism.
The Green Bank attendees spoke of "intelligence" as a generic kind of adaptation,
and thus implicitly assumed that all intelligences would be fundamentally
similar. This assumption was critically important to SETI-Science because
it underwrote the assumption that we could understand messages composed
by an ETI. Sagan developed an explicit rationale for the assumption. Although
he did not use this term, philosophers of science call his rationale "uniformitarianism."
Proponents of uniformitarianism claim that, because the universe is essentially
one place, composed everywhere of matter and energy as we know it, and governed
by natural laws that apply everywhere in it, natural selection will tend
to produce similar solutions to adaptive pressures that are, themselves,
Sagan began the section of Intelligent Life in the Universe that
dealt with uniformitarianism by reminding the reader that the matter found
on Earth is identical to that in remote parts of the universe, and that
"the same interactions occur, and the same laws of nature govern their motion."
He later made the additional point that, although we are unable to know
what the specific characteristics of an ETI might be, we do know that the
laws of physics are universal in character.33 Sagan's point was
that the evolutionary histories of all intelligent beings would have a common
experience at their core because those evolutionary paths would be shaped
by matter, energy, and forces that are the same everywhere. Thus, the kind
of intelligence each of those species would evolve would be similar.
Indeed, because human intelligence is one example of this general phenomenon,
Sagan implied that all intelligence would be humanoid. Sagan returned
to this cornerstone theme of uniformitarianism repeatedly in his popular
writings and television programs. In his Pulitzer Prize winning reflections
on human intelligence, Dragons of Eden, Sagan spoke of a "resonance
... between our brains and the universe" that would also characterize intelligence
everywhere because they "all must come to grips with the same laws of nature."
Sagan believed that, as a result, "we will have little difficulty in understanding
each other."34 A few years later, in his hugely popular television
series Cosmos, Sagan acknowledged that ETIs are likely to be different
from us and then asked, "How could we possibly understand their messages?"
His answer was that the laws of nature, which "are everywhere the same,"
constitute "the language of science" and will thus serve as a kind of Rosetta
Stone that will allow all intelligent beings to communicate with each other.35
For Sagan, these five basic tenets of SETI-Science supported an inevitable
conclusion that he called the principle of
mediocrity. This was the core idea Sagan wanted to disseminate in Intelligent
Life in the Universe.
The principle of mediocrity
A key phrase in the deliberations of the Green Bank conferees was their
reference to "the unexceptional nature of the sun and, by extension, the
solar system." The idea that there is nothing exceptional about our sun,
the planets of our solar system, or the intelligent life that evolved on
Earth became the most important assumption of SETI-Science. Sagan called
it the principle of mediocrity and devoted a chapter of Intelligent Life
in the Universe to the idea. For Sagan mediocrity had the quality of a self-evident
given. It was, simply, "the idea that we are not unique."36
In making the assumption of mediocrity Sagan was operating comfortably within
the recent traditions of his field. A number of prominent astronomers had
established a clear trajectory toward mediocrity during the 20th century.
Sir Harold Spencer Jones, Astronomer
Royal, published a popular exposition of ETI science in 1940, Life on
Other Worlds, that Steven Dick called "the standard for a quarter century,
read by scientists, lay persons, and students alike until superseded by
Shklovskii and Sagan's Intelligent Life in the Universe."37
Initially Jones was reluctant to embrace the possibility of ETIs due to
the "tidal pull" theory of how planets were formed. This theory, advanced
by Sir James Jeans, was especially popular
during the 1920s and 1930s (see Jeans-Jeffreys
tidal hypothesis). It suggested that planets were rare occurrences.
By the 1940s Jeans' theory had begun to fall out of favor. In 1942 Jeans
himself discussed the possibility of life elsewhere and noted that, in light
of the new insights astronomers were developing about the immensity of the
universe, "although planetary systems may be rare in space, their total
number is far from insignificant."38 By the time Jones released
the second edition of his book in 1952, the year before Sagan's epiphany
while listening to Stanley Miller, Jones had overcome his reticence about
Wherever in the Universe conditions are suitable
for life to exist, life will somehow come into existence as it has come
into existence on Earth.... With the Universe constructed on so vast a
scale, it would seem inherently improbable that our small Earth can be
the only home of life.39
On the eve of the publication of Cocconi and Morrison's paper Harold Shapley,
Director of the Harvard Observatory, similarly wrote an "obituary ... of
anthropocentrism in our description of the universe." He urged humans to
prepare themselves for a "fourth adjustment." Having come to grips with
the facts that the Earth orbits the sun instead of the other way around,
and that ours was a relatively humble star in an inconspicuous corner of
an unspectacular galaxy, and after having "accepted rather cheerfully the
Darwinian evidence and argument of our animal origin," Shapley now urged
us to get used to the fact that we are not the only intelligent beings in
the universe. He claimed that "whenever the physics, chemistry and climates
are right on a planet's surface, life will emerge, persist, and evolve."40
In one of his original passages in Intelligent Life in the Universe,
Shklovskii credited the German astrophysicist and early SETI supporter Sebastian
von Hoerner with being the first to make
the mediocrity point in the context of searching for ETI. In 1961, the same
year as Green Bank, von Hoerner wrote, "The one basic assumption we want
to make can be formulated in a general way: Anything seemingly unique and
peculiar to us is actually one out of many and is probably average."41
In the following year Ronald Bracewell,
a radio astronomer who was one of SETI's friendlier critics for decades,
wrote that, "Conditions suitable for intelligent life are believed to be
widespread in our galaxy, and the main gap in our knowledge is that we don't
know whether life has evolved on the planets where the conditions are favorable.
But there is no reason to think it couldn't happen elsewhere if it has happened
Sagan was claiming that earthlike planets were likely in the universe and
that, as a consequence, the evolution of earthlike beings was also
common. In doing so he was not simply positioning himself on a recent trajectory,
he was calling on a tradition that began millennia ago.
|Fig. 3. The humanoid ETIs of Close
Encounters of the Third Kind 43
SETI constructed within the boundaries of the traditional ETI discourse
Like the traditional ETI discourse, SETI assumed that ETIs would be humanoid.
Both did so by ignoring the question of what the precise "nature"
of intelligent beings might be like, leaving the reader to assume it would
be similar to the intelligence with which we are most familiar, viz., our
own. Prior to the 1960s the ETI discourse is virtually silent on the questions
of what an ETI's cognitive structure, consciousness, and intelligence might
be like. There were frequent speculations about what ETIs' external appearances
might be like, but questions about their possible cognitive structures,
consciousnesses, and intelligences did not occur regularly until just about
the same time the SETI project was getting underway. The work of one exceptional
scientist suggests that this need not necessarily have been the case.
Bernard le Bovier de Fontanelle was the
first scientist to offer plausible insights into possible non-humanoid
ETIs. He was also the last to do so for almost three centuries.
He employed analogical reasoning (see argument
from analogy) to modify one aspect of human cognition and then followed
the implications of that all the way to the possibility that intelligent
beings may be inherently incapable of engaging each other. This is the very
issue that later inspired the expansion of the ETI discourse while coming
to haunt SETI. As Fontenelle wrote in Conversations on the Plurality
It's quite possible we're missing a natural
sixth sense that would teach us many things we don't know. This sixth
sense perhaps exists in some other world where they lack one of the five
we possess. Perhaps there are really a great number of natural senses,
but in the division we've made with the inhabitants of other planets only
five have fallen to us, with which we're content because we don't know
of the others. Our sciences have certain limits which the human understanding
has never been able to pass; there's a point at which they suddenly fail
us. The rest is for other worlds, where some of what we understand is
The methodology Fontenelle used to construct his non-humanoid ETIs began
with human cognition. He then tweaked this in some manner and imagined the
changes that such a modification would produce in the new being's consciousness.
This methodology was not used again to construct plausible ETIs until, ironically,
the 1960s. Although the assumptions of SETI-Science rested comfortably within
an established intellectual framework which assumed that intelligent extraterrestrials
possessed a humanoid intelligence, that framework was about to be challenged,
for the first time, at the very moment SETI's organizers invoked it.
By assuming that radio astronomy was a logical choice for any intelligent
being that wished to communicate across interstellar distances, SETI's organizers
proudly claimed that "for the first time in human history it has become
possible to make serious and detailed experimental investigations of this
fundamental and important problem." 45 Sagan argued that they
had demonstrated that the question of whether ETI exists "is amenable to
experimental testing. It has been removed from the arena of pure speculation.
It is now in the arena of experiment." 46 The ETI discourse was
"about to enter an experimental phase, after several millennia in which
the subject was amenable only to somewhat murky speculation." 47
Sagan and his colleagues did not believe they were changing the ETI discourse;
they thought they were testing the central question around which it had
always been constructed.
At the seminal Green Bank meeting SETI's organizers used the Drake Equation
to frame a conversation in which they informally concluded, on the basis
of a small number of bold assumptions, that it was plausible to assume that
ETIs exist and could be sending us messages we would understand.
The Green Bank discussion was elaborated and popularized by Sagan into the
six core assumptions of SETI-Science: that the Drake Equation identified
all the variables relevant to determining if ETIs exist; that life would
inevitably arise on Earth-like planets; that nature repeats successful adaptations;
that intelligence is a successful adaptation, if we don't use it to destroy
ourselves; that all intelligences are similar enough to permit communication
among them; and that communication was likely to be by radio when over interstellar
distances. Sagan fashioned the middle four assumptions into the principle
of mediocrity. SETI-Science was constructed within the boundaries of the
traditional ETI discourse, which assumed that the "nature" of ETI's intelligence
was similar to ours. Indeed, SETI-Science offered a formal rationale, uniformitarianism,
for why this was likely. Although SETI's architects claimed they were engineering
an important enhancement to the traditional ETI discourse by placing it
on rigorously experimental grounds for the first time, they were leaving
its most important assumption unchallenged. By establishing that SETI was
plausible, SETI's organizers successfully negotiated the first phase of
their project's institutionalization inside NASA, where SETI was thought
of as a part of NASA's broader mission to search for extraterrestrial life.
However, NASA's Apollo mission to
land men on the Moon and Viking mission to
land probes on Mars dominated NASA's SETL efforts until its success in 1976.
Fifteen years passed before NASA turned serious attention to SETI.
2. Steven J. Dick, "The Search for Extraterrestrial
Intelligence and the NASA High Resolution Microwave Survey (HRMS): Historical
Perspectives," Space Science Reviews, 64 (1993): 100.
3. David W. Swift, SETI Pioneers – Scientists Talk About Their
Search for Extraterrestrial Intelligence (Tucson: University of Arizona
Press, 1990), 59.
4. http://scifun.chem.wisc.edu/Calendar/FrankDrake/FrankD_stars.jpg, accessed
10 April 2009.
5. George Basalla, Civilized Life in the Universe – Scientists
on Intelligent Extraterrestrials (New York: Oxford University Press,
6. See Percival Lowell, Mars (London: Longmans, Green and Co.,
1895), and Mars as the Abode of Life (New York: The Macmillan Company,
1908). 7. Swift, 67.
8. J. P. T. Pearman, "Extraterrestrial Intelligent Life and Interstellar
Communication: An Informal Discussion," in A. G. W. Cameron, ed., Interstellar
Communication (New York: W. A. Benjamin, 1963), 287–93.
9. Steven J. Dick, The Biological Universe – The Twentieth-Century
Extraterrestrial Life Debate and the Limits of Science (New York:
Cambridge University Press, 1996), 427.
10. www.isepp.org/.../Phillip_Morrison.jpg, accessed 10 April 2009.
11. Giuseppe Cocconi and Philip Morrison, "Searching For Interstellar
Communications," Nature 184 (September 1959): 844.
12. Swift, 73.
13. Pearman, 289.
14. See, e.g., William Poundstone, Carl Sagan – A Life in the
Cosmos (New York: Henry Holt and Co, 1999), 25.
15. Frank D. Drake, "How Can We Detect Radio Transmissions From Distant
Planetary Systems?," reprinted in Cameron, 167.
16. Robert Shapiro, Origins: A Skeptic's Guide to the Creation of
Life on Earth (New York: Summit Books, 1986), 99.
17. A. Oparin and V. Fesenkov, Life in the Universe (New York:
Twayne Publishers, 1961), 239.
18. Dick, Biological Universe, 430.
19. Pearman, 290.
20. Convergence is a well-established phenomenon in evolutionary biology.
It is the separate evolution, in different locations or at different times,
of the same adaptation in unrelated animals. Dramatic examples of convergence
include the facts that vision has evolved independently at least forty
times, employing nine different kinds of eyes, and that flight has evolved
at least five times. See, e.g., Jack Challoner, The Science of Aliens
(New York: Prestel, 2005), 55.
21. Not long after Green Bank, Lilly's research was questioned by some
when he published articles about the insights that he believed were available
by taking LSD. Although Sagan remained friendly with Lilly, visiting his
dolphin research lab on a number of occasions, the proponents of SETI-Science
stopped citing Lilly's work.
22. Pearman, 290.
23. Keay Davidson, Carl Sagan – A Life (New York: John
Wiley & Sons, 1999), 129.
24. Robert Bieri, "Humanoids on Other Planets," American Scientist,
52 (1964): 457.
25. Pearman, 290.
26. Ibid., 291.
28. Ibid., 292.
29. Iosef S. Shklovskii, "Is Communication Possible with Intelligent Beings
on Other Planets," reprinted in Cameron, 11.
30. Davidson, 150.
31. Iosef Shklovskii, Five Billion Vodka Bottles to the Moon –
Tales of a Soviet Scientist, Mary Fleming Zirin and Harold Zirin,
trans. (New York: W.W. Norton, 1991), 251.
32. Nicholas Rescher, The Limits of Science (Berkeley: University
of California Press, 1984), 174.
33. I. S. Shklovskii and Carl Sagan, Intelligent Life in the Universe
– Being a Translation, Extension, and Revision of I .S. Shklovskii's
Universe, Life, Mind, Paula Fern, trans. (New York: Delta, 1966),
34. Carl Sagan, The Dragons of Eden – Speculations on the Evolution
of Human Intelligence (New York: Ballantine, 1977), 242–3.
35. Carl Sagan, Cosmos, Public Broadcasting System (1980), Chapter
XII, "Encyclopedia Galactica," minute 28.
36. Shklovskii and Sagan, 357.
37. Dick, The Biological Universe, 54.
38. James Jeans, "Is There Life on the Other Worlds?" Science
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39. Harold Spencer Jones, Life on Other Worlds, 2d ed. (London:
English Universities Press, 1952), v–vi.
40. Harlow Shapley, Of Stars and Men (New York: Beacon Press,
1958), 1, 98.
41. Sebastian von Hoerner, "The Search for Signals from Other Civilizations,"
in Cameron, 272.
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44. Bernard le Bovier de Fontenelle, Conversations on the Plurality
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45. Carl Sagan, ed., Communication With Extraterrestrial Intelligence
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46. Carl Sagan, Cosmic Connection (New York: Cambridge University
Press, 1973; reprinted as Carl Sagan's Cosmic Connection – An
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of the Royal Society of London 189 (6 May 1975): 143.
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