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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About all we can do at present is to
evaluate the reports, although suf-
ficient desire might make more than
this possible (in the Exeter sighting
described below, observers could have
actually waited, fully equipped with
high-speed cameras and other devices,
for the return of the objects). Profes-
sor J. Allen Hynek (1966), the Director
of the Observatory at Northwestern Uni-
versity, and for the past 18 years con-
sultant to the Air Force in their study
of UFO sightings, has often stated that
to make progress we must accept the
fact that the UFO's do exist — as re-
ports. The Air Force and several pri-
vate groups have accumulated bulging
film of these reports, containing every-
thing from detailed interviews to the
remnants of pancakes submitted by a
witness who claimed he had received
them from a space man! These reports
and the many which will be obtained
in the future (using hopefully better
means of information gathering) are
the data with which we must work,
and the only data so far available.
What can we do with them?
One obvious approach is to propose
as many possible interpretations as can
be devised and then to evaluate the
data in terms of these hypotheses. The
process will be a circular one, in which
hypotheses are formulated on the basis
of the data, and the data are then re-
examined in terms of the hypotheses.
In the following paragraphs, five hy-
potheses are discussed and then a few
representative sightings are considered.
The subject has been reviewed by
several authors in book form, often
competently, but virtually always with
some degree of prejudice (for: Hall,
1964; Keyhoe, 1960; Lorenzen, 1962,
1966; Michel, 1958; Vallee, 1965; Val-
lee and Vallee, 1966— against: Menzel
and Boyd, 1963).
I. Extraterrestrial Spaceships
or Other Machines
Although earlier observers usually
interpreted the UFO's in terms of
miraculous religious events, most UFO
observers during the past 19 years have
suggested that the objects which they
observed were extraterrestrial space-
ships.
Can we eliminate the spaceship hy-
pothesis in any rigorous scientific man-
ner? Logically one might think of two
approaches: either we must show in
each and every instance ever reported
that the object was not an extraterres-
trial spaceship, or we must show by
some sort of scientific logic that it is
impossible for extraterrestrial beings
to visit us.
Obviously, we cannot show in every
case that a purported UFO was not an
extraterrestrial spaceship. The data
may not be available, and the events
cannot be repeated. Furthermore, in
several instances, very detailed data do
exist in relation to a sighting, and yet
it cannot be rigorously stated that the
UFO was not an extraterrestrial ma-
chine.
Nevertheless, this approach has been
followed in an attempt to eliminate this
hypothesis, notably by Professor Don-
ald Menzel, Director of the Harvard
Observatory (Menzel and Boyd, 1963)
and by the United States Air Force.
Menzel is aware of the logical limita-
tions, but he takes a statistical ap-
proach. He reasons that since many
sightings can be positively eliminated
as extraterrestrial spaceships, those
which cannot could be if only more
data were available. This is an excel-
lent example of the inductive form of
reasoning which has been so produc-
tive in science. Can we confidently
apply it in relation to the UFO phe-
nomena? To do so, the cases for which
ample data exist and which prove not
to be spaceships must be representative
of the class as a whole. To many of us
this seems unlikely, since other cases
fortified with considerable data cannot
be eliminated as extraterrestrial ma-
chines, and in many ways they appear
to have little in common with the cases
which can. On purely formal grounds,
then, we cannot be absolutely con-
vinced by Menzel's approach.
It is also logically unreasonable to
say with absolute certainty that it is
impossible for extraterrestrial beings to
visit us. Although we know a great
deal about the universe, we do not yet
know enough to make such an all-
inclusive negative statement. Never-
theless, many of the arguments are
highly compelling, and two are espe-
cially worthy of our attention.
The first argument is that the UFO's
contravene the laws of nature, or more
properly, that they are contrary to our
experience. It is first assumed that they
could not originate within our solar
system because only the earth harbors
intelligent life, and then it is reasoned
that because of the extreme distances
between stars they could not be visitors
from some other planetary system. My
initial contact with the UFO problem
came because of my doubts in relation
to the first assumption (Salisbury,
1962; 1964; 1966).
Certainly we have no conclusive or
even compelling evidence that Mars
might support an intelligent civiliza-
tion. We do, however, have a number
of observations which seem to be in
agreement with this assumption. The
network of lines referred to as the
canals still defies explanation in terms
of nonintelligent phenomena, although
such an explanation may well be ap-
parent when we obtain more data
about Mars. The satellites of Mars,
with their almost perfectly circular,
equatorial orbits and their small size
have certain of the characteristics of
artificial satellites. Brilliant flares of
light occasionally seen on the surface
of Mars are too short in duration and
too bluish-white in spectral quality to
be similar to our volcanoes, yet they
are too long in duration to be readily
explainable as meteorite impacts. An
occasional associated white cloud
would seem to eliminate them as re-
flections. It is even possible, if one is
willing to stretch the imagination a bit,
to find evidences for intelligence in the
Mariner photographs of Mars. These
ideas have recently been discussed in
considerably more detail elsewhere
(Salisbury, 1966).
There was an interesting correlation
from 1948 to 1957 in the number of
UFO sightings per unit time and the
closeness to the planet Mars (Fig. 1).
This was shown by Vallee and Vallee
(1962; 1966) to be expected on sta-
tistical grounds less than one time in a
thousand. Both Venus and Jupiter are
far more prominent in the skies than
Mars (both have often been misin-
terpreted as UFO's), and yet no such
correlation exists with their apparent
brightness in the skies and the number
of UFO sightings.
Assuming that there is no intelli-
gence on Mars and that the UFO's
would have to cross interstellar space,
can we really state with confidence that
this is an impossibility? Do we know
so much? Of course we do not. We
are even searching for possible solu-
tions to the problem of interstellar
travel.
Perhaps the most compelling "im-
possibility" argument is the reported