Symposium on unidentified flying objects: hearings before the Committee on Science and Astronautics, U.S. House of Representatives, Ninetieth Congress, second session, July 29, 1968.

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able likely accompaniment of star formation, that the solar system in
other words is a fairly common event in the galaxy and is not unique.
There are laboratory experiments on the origin of life
'
in which the
early conditions on earth have been duplicated in the laboratory. It
turns out that at least the molecules fundamental to living systems, are
produced relatively easy, physics and chemistry apparently made in
such a way that the origin of life may be a likely event.
Beyond that it is difficult to do laboratory experiments, because
evolution takes billions of years, and scientists aren't that patient.
Therefore, it is just a question of intelligent and knowledgeable
estimates.
Here, some scientists believe that the evolution of intelligence and
technical civilization is very likely. Others believe it is a very remark-
able and unusual event and by the merest fluke did it happen here.
I don't think that this is the place to go into this very difficult ques-
tion in any great detail. Let me merely say that much more important
than these uncertainties is the question of the life of a technical civil-
ization, judging from the events on the earth, one might say the likeli-
hood of our civilization lasting only a few decades more, might be a
fairly high probability, and if that is typical of other civilizations,
then it is clear there aren't any other humans around.
On the other hand, if civilizations tend to have very long lifetimes,
it may be there are large numbers of technical civilizations in the
galaxy.
Now, one thing is clear, which is this: If there are other technical
civilizations, any random one of them is likely to be vastly in advance
of our own technical civilization. For example, we are only 10 or 15
years into having the technology of interstellar communication by
radio astronomy. It is unlikely there is any other civilization in the
galaxy that is that backward in their technical expertise.
Mr. MILLER. Doctor, didn't Sir Bernard Lovell receive electrical
pulses he can't explain?
Dr. SAGAN. Yes, sir. There are now five objects in the heavens called
pulsars, which are objects which are sending out radiation which is
modulated with a frequency of about one per second; also there are sub-
modulations. There are a variety of hypotheses to explain these things,
some of which involve the oscillations of very old stars. There are
certain difficulties with each hypothesis. The first suggestion made by
the British at Cambridge,when they encountered this phenomenon was
perhaps it was a beacon of some extraterrestrial civilization. That is
not now their favored hypothesis. It is not clear that that is totally
absurd,but in fact the scientific method to be used in that case is rather
similar to the one to be used in this case. That is, it is a puzzling phenom-
enon. One therefore excludes all physical explanations that one pos-
sibly can before going to the much more hypothetical possibility of
intelligence being involved.
So,that is the present state of work in that field. For data gathering
to get better information, and the refinement of the purely physical
hypothesis.
Well,I was saying that if there are other civilizations many of them
are likely to be far in advance of our own,and this,therefore raises the
question of how likely it is that they can traverse interstellar space
and come from planets or some other star to here.