Scientific Study of Unidentified Flying Objects (the Condon Report, complete, three volumes)

construct and operate tllat the measurements required have not yet been
attempted.
Nevertheless, there is strong inferential evidence that such sharp
gradients do exist in the atmospher~ (see Section VI, Chapter 4), but
expf.lriments c~pab1e of detecting such gradients have not been made.
The fact that, for example, a temperature change of 10° C over a dis-
tance of I em. has not yet been observed in the free atmosphere is not
proof that such gradients do not exist.
The following set of hypotheses were considered as possible ex-
planatimls for each of the UFO phenomena studied:
1. That the phenomenon was caused by a mechanical or other de-
vice designed for tra.l~portation, surveillance, or other related
objectives, and which mayor may not have been controlled by
extraterrestrial beings.
2 That the phenomenon was caused by a conventional airplane,
ballocn, blimp, or other man-made device.
3. That it was a natural phenomenon, star, meteor, etc., per-
haps seen under unusual circumstances;
4. That it was an unknown natural phenomenon;
5. That it was a product of unusual conditions of radar or
optical propagation, possibly involving natural or artificial
nhenomena observed and/or recorded in unusual aspect.
The purpose of the investigation reported in this chapter was to
determine, for the 35 cases included, the extent to which hypothesis
~o. 5, either alone or in combination with Nos. 2 and 3 could satis-
factorily account for the circumstances of the UFO report. In each
case the probability that some other hyporhesis, such as Nos. I or 4.
could more satisfactorily account for the sighting h~d to be evaluated.
There is always the nanger in this sort of procedure that the
true explanation for a parti8ular ~vent i~ not contained in a given
set 01:.2 priJri hypotheses. One obvious omission from the list above
is the hypothesis that a particular UFO rerport was a hoax. Since
174
construct and operate that the measurements requireJ have not yet been
attempted.
Nevertheless, there is strong inferential evidence that such sharp
gradients do exist in the atmospheu (see Section VI, Chapter 4), but
expf.lriments c~pablc of detecting such gradients have not been made.
The fact that, for example, a temperature change of 10° C over a dis-
tance of 1 em. has not yet been observed in the free atmosphere is not
proof that such gradients do not exist.
The following set of hypotheses were considered as possible ex-
planatians for each of the UFO phenomena studied:
1. That the phenomenon was caused by a mechanical or other de-
vice designed for tra.l~portation, surveillance, or other related
objec:tives, and which mayor may not have been controlled by
extraterrestrial beings.
2 That the phenomenon was caused by a conventional airplane,
balloen, blimp, or other man-made device.
3. That it was a natural phenomenon, star, meteor, etc., per-
hap.> seen under unusual circumstances;
4. That it was an unknown natural phenomenon;
5. That it was a product of unusual conditions of radar or
optical propagation, possibly involving natura' or artificial
nhenomena observed and/or recorded in unusual aspect.
The purpose of the investigation reported in this chapter was to
determine, for the 35 cases included, the extent to which hypothesis
:-Jo. 5, either alone or in combination with Nos. 2 and 3 could satis-
factori ly account for the circumstances of the UFO report. In each
case the probability that some other hypothesis, such as Nos. I or 4,
could more satisfactorily account for the sighting had to be evaluated.
There is always the rlanger in this sort of procedure that the
true explanation for a parti8ular event i::j not contained in a given
set oi::! pri'JY'i hypotheses. One obvious Qmission from the list above
is the hypothesis that a particular UFO rerpf)rt was a hoax. Since
174