]]]]]]]]]]]       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]

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
   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
   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
   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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