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]]]]]]]]]]] WE ARE ALONE IN OUR GALAXY [[[[[[[[[[[[[[[[[
Frank J. Tipler (11-26-1988)
From New Scientist, 7 October 1982, pp. 33-35
(Dr Frank J. Tipler is Associate Professor of Mathematical
Physics at Tulane University, New Orleans)
[Kindly uploaded by Freeman 10602PANC]
SUMMARY:
Faith in the existence of extraterrestrial intelligent life is so
great that many astronomers urge governments to divert scarce
research funds into the search for extraterrestrial intelligence.
Yet there is no evidence that such life exists, and powerful
arguments that it does not.
* * *
The possible existence of intelligent extraterrestrial life
has always fascinated mankind. During the past 25 years several
astronomers, notably Carl Sagan and Frank Drake of Cornell
University, and Philip Morrison of the Massachusetts Institute of
Technology, have proposed that we search actively for such beings
by scanning the sky for their signals, using radio telescopes.
Estimates for the cost of such a search range from ten to several
thousand million pounds, and even at the lower end of this range
the cost is very great compared with most scientific research.
Before conducting such an expensive experiment, we should
consider carefully whether the endeavour has a significant
likelihood of success. I believe that such a search is doomed to
failure, and that we represent the only intelligent species ever
to exist in our Galaxy, and quite possibly the only intelligent
species ever to exist in the entire visible universe.
Before I give the reasons for my belief I should define what I
mean by the expression ``intelligent being''. By ``intelligent
being'' I mean a member of a living species that is capable of
developing a technology comparable to ours, and which is, like
the human species, interested in using this technology to
communicate with other intelligent species, and is interested in
exploring and or colonising the Galaxy. One might argue that
this is too restrictive a definition, but this is the only kind
of extraterrestrial life that searches with radio telescopes
could possibly detect.
I have two basic reasons for my disbelief in the existence of
extraterrestrial intelligent beings. First, all the great
contemporary experts in the theory of evolution -- Francisco
Ayala, Theodosius Dobzhansky, Ernst Mayr and George Simpson --
are unanimous in claiming that the evolution of an intelligent
species from simple one-celled organisms is so improbable that we
are likely to be the only intelligent species ever to exist.
Secondly, I have made calculations that indicate that
interstellar travel is not only feasible but could be achieved
quite inexpensively by an intelligent species only slightly in
advance of us. If such a species existed, there would, therefore,
be evidence of its existence on Earth or in the Solar System.
How do these two arguments look in detail? The evolutionists
contend that the development of intelligent life is extremely
improbable because there is an enormous number of evolutionary
pathways leading from simple one-celled organisms to many-celled
creatures, and, in their opinion, only a very few of these
pathways include intelligent beings. One might think that
intelligence would be a property that would confer an enormous
selective advantage on a species, and this would cause
intelligence to evolve; but natural selection is more complex
than this. It acts upon the entire body of a creature, not just
on a creature's neurological system. In the vast majority of
cases, a genetic change that results in an increase in the
complexity of the neurological system will cause a corresponding
adverse change in some other bodily characteristic that the
creature needs for its immediate survival. The adverse change
outweighs the improvement in intelligence, and the creature does
not survive in order to pass on the increase in intelligence to
descendants.
Even more important than this trade-off effect is the fact
that natural selection has no long-term foresight. Any genetic
change that occurs must act immediately to increase the survival
probability of a creature, or it will not be selected for.
Evolution cannot accept a temporary net decrease in ``fitness'',
in the Darwinian sense, in order to achieve a net increase in
fitness several generations into the future. So the evolution of
a given complex system can be expected to occur only once,
because such a system requires the simultaneous appearance of
many new genes or a change in several old genes together. The
eye is an apparent counterexample. It occurs in many different
forms in animals as different as vertebrates and cephalopods
(octopus), whose eyes are very similar although their common
ancester [sic] lies far back in Precambrian times, more than 600
million years ago. This seems like independent evolution of a
complex system. But Professor Leonard Ornstein of the City
University of New York, has suggested that the common ancestor
already had an eye. Ornstein also points out that this
hypothesis can now be tested by comparing the structural genes
controlling eye development in cephalopods and and [sic]
vertebrates. Modern techniques in molecular biology, developed
for genetic engineering, make this possible, although the
experiment has not yet been carried out.
The ability to develop advanced technology is also built upon
a very complex biological system. We would therefore expect that
it is exceedingly unlikely to appear more than once. The
improbability is so great, in the opinion of many evolutionary
experts, that we are likely to be the only intelligent species in
the Galaxy, if not the visible Universe.
To my mind, however, the second argument is even stronger than
the evolutionary argument. If ``they'' existed, they would
already be here. The argument assumes that interstellar travel
is feasible, which may seem an extreme claim. The human species
had, however, already launched four very primitive interstellar
probes: Pioneers 10 and 11, and Voyagers 1 and 2. All these have
speeds in excess of the escape velocity from the Solar System,
and had they been so aimed they could have been targeted to enter
any one of several nearby solar systems in about 100 000 years'
time. These probes were not so aimed, because they were designed
for other tasks and lacked the instrumentation to explore other
solar systems. We do not lack the necessary rocket technology to
begin interstellar exploration using robot probes; what we lack,
and only barely, is the proper instrumentation, the computer
technology.
What sort of computer technology would be required? I propose
that the proper guidance computer should be what I call a von
Neumann machine. This is a computer with intelligence close to
the human level, capable of self-replication and capable, indeed,
of constructing anything for which it has plans, using the raw
materials available in the solar system it is aimed at. An
interstellar space-probe carrying a von Neumann machine could
work as follows. On entering a solar system, the probe would
make several copies of itself using matter in the form of
asteroids, comets and similar debris. According to present
astronomical theories, such debris should be present in virtually
every stellar system whether or not it contained planets. These
copies of the probe would then be launched on to other stellar
systems, where the process would be repeated, while data were
sent back to the home station. Eventually, all the stars in the
Galaxy would be reached by some descendant of the single original
probe. The Galaxy would be explored for the price of one von
Neumann machine!
Once copies of the probe have been launched, the first von
Neumann machine would enter a stellar system can concentrate on
exploration. It could be programmed to construct whatever
devices it needs for the task, and even to colonise the target
system with replicas of the species that constructed the first
such probe. All the information needed to synthesise a human
being is coded in the DNA of a fertilised human egg cell. This
information could in principle be stored in the memory of a von
Neumann machine, which could be instructed to synthesize an egg
and place the ``fertilised cell'' in an artificial womb.
Remember that the probe has all of the raw materials of a solar
system at its disposal, and all the energy it needs from the
output of the central star in that system. In nine months there
would be a human baby in the stellar system, and this could be
raised to adulthood by surrogate parents, constructed by the von
Neumann machine. A first generation of people could thus occupy
a space station also constructed by the machine, or even be set
loose on a planet.
This colonisation scenario could be played out for any form of
life that even remotely resembles the forms with which we are
familiar. If for some reason the ``parent'' species did not
which to ``colonise'' the Galaxy with its own form, they could
have just as easily have instructed the probe to seed any
suitable planet with one-celled organisms. Such a dispersal of
single-celled organisms throughout the Galaxy has been proposed
by Francis Crick, co-discoverer of the structure of DNA, who
calls it ``direct panspermia''; the advantage of the von Neumann
machine lies in the range of options open to the original
constructors of the first probe, thanks to the probe's
flexibility. This could colonise any stellar system that
contained enough debris to manufacture a space colony; or they
could seed the Galaxy with simple life forms and leave evolution
to take its course; or they could simply explore.
Such a probe could make contact with intelligent beings
whatever their level of technological development. This gives
von Neumann probes an enormous advantage over radio where the
search for extraterrestrial intelligence (SETI) is concerned.
With radio searches, we are restricted to searching for
civilisations that have developed similar technology to our own,
but which have not yet begun interstellar travel, nor developed a
more effective signaling technique. There are no such
restrictions with probes. A spaceship, built by a probe out in
the asteroid belt, in front of Buckingham Palace, say, would have
been noticed long before radio was invented on Earth.
A key difficulty with SETI proposals is that there is an
extremely high probability that these expensive experiments will
tell us absolutely nothing. If a signal is received, well and
good; but what if nothing is detected? Does that mean there is
nobody out there, or that we are listening on the wrong frequency
or at the wrong time, or with the wrong equipment altogether?
Beings out there might have better things to do than send out
signals for centuries in the silly hope that someone might
listen. I have posed these, and similar questions to SETI
enthusiasts, but have never had a reply. I firmly believe that
the proponents of SETI should give serious thought to the
possibility of failing to detect a signal, and the meaning of
such a failure, before an expensive SETI project is funded. With
von Neumann probes there is no such difficulty. One is always
certain to get some useful information back from a successful
probe.
The main difficulty with the probe idea is that it involves
technology in advance of ours, and therefore cannot be proved
feasible. However, the great mathematician John von Neumann
proved that a self-reproducing universal constructor is possible
in principle -- that is why I have named the probes in his honour
-- and computer scientists believe that such machines will be
built within a century. Assuming that such machines are built
once, they will then make copies of themselves, and must become
cheap. So I have calculated the cost of a von Neumann probe on
the basis of fuel costs. The price tag, in round terms, is
[pound sign] 2000 million. This is the cost of exploring the
entire Galaxy, yet it is within the means of many private
organisations, let alone governments, today.
An interstellar probe using our rocket technology would need
40 000 years before it reached the nearest stellar system and
began to send back information. Is it reasonable to consider
such a long-term project? I think it is. A group need maintain
its interest in the project for only a few years; what happens
after the probe is launched will not affect the exploration/
colonisation of the Galaxy, and a single successful probe
launched by any species anywhere in the galaxy makes this
exploration/colonisation inevitable. People may be motivated by
an idealistic vision of galactic exploration, or by a desire to
spread their own image throughout the Galaxy. Either way, any
society would be likely to have people who would be attracted to
such a project even if it would not be completed until long after
they were dead.
Even SETI proposals assume that such enthusiasts exist. These
proposals require that somewhere in the Galaxy there is a society
willing to broadcast signals for thousands or millions of years
before receiving a reply. This is, if anything, less plausible
than the idea that a group could hold together for the few years
necessary to build and launch a von Neumann probe. Even using
our primitive rocket technology it would take only 300 million
years to cover the entire Galaxy with such probes, and this is
such a short time compared with the age of our Galaxy of 10
thousand million years that I conclude that if intelligent beings
existed their probes would be here. Because they are not here,
no such beings exist.
This is a bare outline of my argument against the existence of
extraterrestrial intelligent life. I have presented a more
detailed analysis in a series of papers published in the
Quarterly Journal of the Royal Astronomical Society, and I have
challenged Carl Sagan, the most well-known believer in ETI, to a
``letter debate'' on this question. Such a debate consists of an
exchange of letters between two opponents, with the letters being
published after a year or so of exchange. Professor Sagan has
yet to respond to my challenge. I hope he will debate. Then
each reader would have a chance to decide for himself or herself
if we are really alone in the Universe.
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