Icarus 32, 473-475 (1977)


                            NOTE

           The Absence of Extraterrestrials on Earth
                  and the Prospects for CETI


                   David W. Schwartzman
           Department of Geology and Geography,
                    Howard University,
                  Washington D.C. 20059

         Received March 24, 1977; revised May 16, 1977


The absence of extraterrestrials on Earth in spite of the
probable existence of a ''Galactic Club'' is a result of our
nearly unique position on the verge of becoming a member. This
supports the view that we are under surveillance by
extraterrestrial intelligence, and reduces the likelihood of
contact by radiotelescopes.



    There is a posibility that the oldest and most advanced
  civilizations on distant stars have in fact reached the level
  of permanent intercomunication and have formed, as it were, a
  club of communicating intellects of which we have only just
  qualified for membership and are probably now having our
  credentials examined. In view of the present chaotic political
  and economic situation of the world, it is not by any means
  certain that we would be accepted.               Bernal (1967)


    The reason they do not intervene in the affairs of Earth is
  due to the fact that cosmic humanitarianism is not alien to
  them.                                        Fialkowski (1977)



The prevailing belief within the scientific community is in the
abundance of extraterrestrial life (ETL), with perhaps millions
of probable civilizations in our own Galaxy. However, a recent
paper by Hart (1975) has called into question this view by a
simple argument: if other advanced civilizations exist they
should have colonized Earth - since they are not here they do
not exist, assuming colonization is a probable strategy of
extraterrestrials. Given this assumption of noncontact the case
is persuasively argued. Physical, sociological, and temporal
objections to the conclusion are dealt with in a convincing way.
For example, explanations which link the lack of colonization to
difficulties in fast interstellar space flight or lack of
motivation are unconvincing, given technological extrapolation
of even present physics and the high probability that at least
one civilization will be interested in galactic exploration (see
also Kuiper and Morris, 1977). Jones (1976) supports this
argument with more detailed calculations of probable
colonization rates.

  Cox (1976) has challenged Hart's argument by a closer look at
the limits to colonization. He argues that the time allowed in
the history of the Galaxy may be too short for colonization to
occur for a _handful_ of civilizations (the physical and
sociological arguments are trivial in comparison). However, even
his assumptions [very conservative, in my opinion, for
technologies close to ''magic'' (Sagan, 1973a)] lead to
colonization in a few million yeals for N > 50,000, where N is
the number of advanced civilizations in the Galaxy. Further, he
points out that colonization is an extreme assumption; things
are much easier if extraterrestrials simply explore and leave
Bracewell probes (Bracewell, 1974). I believe this is highly
probable if N > 1 even if colonization never occurs. Hart
(private communication, 1976) suggests an alternative argument
against N > 1; the first advanced civilization in the Galaxy
would have preceded the second by some millions of years, thus
allowing for complete colonization of the Galaxy by the first.
He argues that since we are not products of this colonization,
we are therefore alone. I differ with this interpretation by
assuming that colonization is not a probable extraterrestrial
strategy, but that surveillance and eventual contact are. This
of course is close to Ball's (1973) zoo hypothesis, which Hart
dismisses as untestable. The search for Bracewell probes in our
solar system is a near recognition of the zoo hypothesis and is
part of the Soviet program for CETI (1975).

  Hart's argument is in sharp contrast to most other estimates
of N, e.g., those of Shklovskii and Sagan (1966). Further, they
argue that ''efficient interstellar spaceflight'' is likely to
be developed by a civilization substantially in advance of our
own. Given their preferred values of N (10e6), lifetime L (10e7
yr), and one contact 1/yr 1/civilization, this results in an
average contact frequency per planet of 10e-5 1/yr for
intelligent pretechnical planetary communities. Sagan notes that
L and the colonization rate might be increased significantly by
the ''feedback effect'' (von Hoerner, 1961) of mutual
communication via simple electromagnetic radiative contact.

  However, Hart's and Jones' arguments are quite convincing
given Hart's simple assumption that ''they'' are not here. Hart
calls the rejection of this assumption the ''UFO hypothesis''
[i.e., UFOs are of extraterrestrial intelligent (ETI) origin].
He dissmisses this by saying that ''since very few astronomers
believe the UFO hypothesis it seems unnecessary to discuss my
own reasons for rejecting it''. Hart is of course correct in
maintaining that very few astronomers believe UFOs are
extraterrestrial craft. Sturrock (1977) found that 1356 members
of the American Astronomical Society estimated the probability
of UFOs being ''alien'' (i.e., extraterrestrial) as 3 percent
compared to a probability of 78 percent for some conventional
explanation. However, 23 percent responded that the UFO problem
''certainly deserves'' scientific study, while 30 percent
responded that it ''probably'' does. Note that although Sagan,
too, dismisses the ''UFO hypothesis'' (Sagan, 1972), he does
suggest, on the basis of previously mentioned contact
frequencies, that extraterrestrial contact may have occurred
within historic times (Shklovskii and Sagan, 1966).

  I believe that a case can be made for the ETI explanation of
at least some UFOs (see, e.g., Friedman, 1975). The definition
of UFOs used in this paper is that of Hynek (1972): those
objects (lights) that remain ''unidentified after close scrutiny
of all available evidence by persons who are technically capable
of making a common sense identification.'' Of course,
surveillance by ETI may be taking place quite independently of
the UFO phenomenon (e.g., by an automatic station in the solar
system). However, in my opinion, the plausibility that at least
some UFOs are of ETI origin is greatly increased by Hart's
arguments. I will not review the case for at least examining the
UFO phenomenon in a serious scientific study. The references
cited above along with others of the ''invisible college''
(Vallee, 1975) have presented this argument well. Rather, the
purpose of this communication is to show that present
surveillance of Earth by ETI is the best reconciliation of
Hart's _arguments_ with those that uphold the probable high
value of N. I hope to encourage the dialogue started at the
Stanford Workshop held in 1974 (Carlson and Sturrock, 1975).

  To summarize, I assume the following: (1) N >> 1; the Galactic
Club (Bracewell, 1974), i.e., a ''vast network of intelligent
civilizations in productive mutual contact'' (Shklovskii and
Sagan, 1966), exists. This means all civilizations in the Galaxy
are much more advanced than we (the step function effect in the
emergence of a civilization capable of communication in the life
of the Galaxy), equivalent to Shklovskii and Sagan's principle
of mediocrity (see Morrison, 1974). (2) UFOs are of ETI origin,
craft of the Galactic Club (following Sagan's arguments for the
likelihood of direct contact). These assumptions provide a
reason behind the obvious lack of ''official contact'' by ETI.
We are unique, not in any geocentric chauvinist sense, but in
the sense of happening to be on the verge of becoming a member
of the Galactic Club.

  The motivation behind the present apparent surveillance by ETI
is speculative, but some reasons can be suggested [see Friedman,
(1975) for a more complete list]. The Galactic Club has a
science of comparative no-ogenics (Kamshilov, 1973),
encompassing exobiology and the laws of the interaction of
civilizations and ''nature''. We are _at present_ a unique or at
least a very rare object of this science, with perhaps 1000
other similar cases in the last 10,000 years (a rate of 0.1
1/yr). Entrance into the Galactic Club may take only a few
hundred years after a civilization is communicative. Perhaps the
observed behavior of UFOs is intended to condition us to the
acceptance of this fact [Vallee's (1975) ''cultural
manipulation'']. This argument is close to the zoo hypothesis
(Ball, 1973). Ball assumes that ''we are unaware of them.'' Many
on Earth are aware of them, even though admittedly most
awareness is of a very primitive, often quasi-religious
character. ''We'' as a world scientific community or planetary
entity are not.

  The main argument that Sagan has offered against the ETI
explanation for UFOs is his Santa Claus analogy, with every UFO
craft representing a separate interstellar visit (Sagan, 1972,
1973b). Friedman (1973) has pointed out the absurdity of this
argument by simply distinguishing between the local surveillance
craft (''UFOs'') and the presumed primary contact vehicles.
Sagan does raise this possibility but dismisses it by saying it
only changes the frequency by 10 to 100 times at most. How he
computed this is not explained. Suppose only one visit has
occurred in the last 10,000 years. Is it really so improbable
that surveillance has continued since then from a base in our
solar system? Sagan maintains that ''looking for UFOs remains an
unprofitable investment of terrestrial intelligence - if we are
truly interested in the quest for extraterrestrial
intelligence'' (1973b). He advocates the search via
radiotelescopes. Yet, he seems pessimistic about the likelihood
of detecting ETI. He argues persuasively that it is ''a great
conceit, the idea of the present Earth establishing radio
contact and becoming a member of the galactic federation''
(1973b), since advanced civilizations would be unlikely to
''make their presence known to emerging civilizations via
antique communication modes'' (1973a).

  Where, then, do we stand on a strategy for CETI? In the light
of the previous discussion a program for CETI should include the
following: (1) Radio (and other parts of the EM spectrum) search
for Type II or Type III civilizations (Kardashev, 1964) among
nearer galaxies (Sagan, 1973a), and a search for Bracewell
probes (USSR Academy of Sciences, 1975). (2) A much more serious
study of the UFO phenomenon to produce ''harder'' data (e.g.,
spectra from glowing UFOs), a systematic search using radar
networks, infrared sensors from space, etc (see Baker, 1968;
McCampbell, 1973). Studies of possible historical ETI contacts
should also be continued. Shklovskii and Sagan (1966) are open
to this approach. Temple's (1978) study of the Dogon mythology
is an example of serious work of this kind. (3) Perhaps the only
method likely to produce positive results: the ongoing effort
via political and social practice toward the creation of a
unified planetary civilization by elimination of obsolete
political economic formations, i.e., passing the entrance
requirements of the Galactic Club. (Bernal, 1967).



  ACKNOWLEDG@ENTS

John Carlson and Michael Hart made helpful suggestions on a
first draft of this paper. Thanks are also given for the helpful
suggestions of a reviewer.



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