Editing UFOs An International Scientific Problem (section)

=== Reflections and Mirages - Menzel’s Views ===

However, it is not only Bluebook that stresses misidentifieds. For about
15 years, [[D H Menzel|Dr. D. H. Menzel]], former Director of Harvard College Observatory,
has been saying that UFO reports fall almost entirely in that category. His
two books11'13, other writings, and many television and lecture discussions
have invariably emphasized that position. It has been of particular scien-
tific interest to me that a majority of his alternative explanations fall
within my own area of interest, atmospheric physics. Consequently I have
examined his arguments rather carefully and must say that they do not at all
convince me. Since I have cited specific examples and discussed specific
objects elsewhere1'8, I shall not give numerous examples here.
But one category of Menzel's explanations that has evidently influenced
Bluebook thinking of recent years (since similar explaining shows up in
official files) deals with "reflection" of light from atmospheric inversions
and "haze layers." Menzel's explanation of the August 20, 1949, Las Cruces
N.M., sighting by [[Clyde Tombaugh|Dr. Clyde Tombaugh]] is a case in point (11, p. 266). Menzel
argues that lights from windows on some house, reflected off an elevated
inversion layer produced the appearance of six yellowish rectangles that
Tombaugh, along with two members of his family, saw shooting across the sky
in that famous sighting. Tombaugh first spotted the geometric array of six
pale-yellow rectangles almost directly overhead. Menzel suggests that they
were reflections of window lights on an inversion layer at which haze had
collected (despite Tombaugh's strong emphasis on the unprecedented transpar-
ency of the air that night!). Since only collimated beams like searchlight
beams can yield distinct spots on haze layers, one seems left only with the
notion that when Menzel says "reflection" he means just that. Let us examine
the possibility that atmospheric inversion layers could yield perceptible
reflectivity at near-normal incidence such as would have to be involved if
Menzel's suggestion is to be acceptable.

For ideally sharp refractive index discontinuities, the Young-Fresnel
equation (see, for example, 14, p. 420) gives the reflectivity R across a 2
discontinuity between two media of relative refractive index n as

   R = [ (n - 1) / (n + 1) ] 2 g

for normal incidence. Even for off-normal incidence angles out to several g
tens of degrees, the order of magnitude of R is well-estimated by that famil-
iar optical relation. Menzel's qualitative discussions about how UFO appari- O
tions stem from reflection off atmospheric discontinuities frequently involve §
such near-normal incidence. Hence the question becomes that of asking about £
how large n can become. For visible light in air at NTP, the refractive index ®
relative to a vacuum is about 1.0003, and temperature effects across an inver- >
sion boundary (even if idealized as mathematically sharp) make changes only
in about the fifth or sixth decimal place of that parameter. Clearly, then,
one will make a gross overestimate of R to go the extreme case of an "inver-
sion" separating standard air from a perfect vacuum, i.c., by inserting into
the Young-Fresnel relation the magnitude n = 1.0003. The result is seen to
be roughly 
   R = 1Q_7

This negligibly small reflectivity could not conceivably yield window-reflec-
tions of the type adduced by Menzel to account for sightings such as Tombaugh's,
despite its grossly overestimating the actual "inversion-layer" reflectivity
that might be encountered in the real atmosphere. Such quantitative consider-
ations are what are not found in Menzel's defense of his discussions of UFO
misidentifications, even in areas where his particular professional background
ought to have made him sense the orders of magnitude likely to be involved.
In the February issue of Air Force/Spacf> Digrrt^^ will be found a Letter
discussing an observation of an odd aerial apparition seen by Lt. Col. R. G.
Hill, and treated by AF/SD as an example of UFO reports that are explainable
if only one looks far enough. I have spoken with Col. Hill to get a few
further details and can only wonder if Menzel's "inversion-reflection" ideas
and Bluebook's misuse of the same have not misled Hill and the editors of
AF/FD. The four luminous discs which Hill saw on a November evening a half
dozen years ago are tentatively explained in Hill's communication as "Possibly
the result of some atmospheric phenomenon that caused two interfacing layers
of air to reflect the light from a nearby source such as the mercury vapor
lamps illuminating the parking lot at the shopping center where these objects
appeared." As I have stated to Col. Hill and to AF/Fb, this is quantitatively
quite out of question, Menzel's and Bluebook's arguments notwithstanding.
Indeed, everyday experience with window-glass, whose refractive index
relative to air is about 1.5, ought to have served to prevent the widespread
misimpression concerning UFOs caused by "inversion-reflections." Window-glass
gives an unimpressive normal-incidence reflectivity of about 4 per cent; yet
it is obvious that it must be orders of magnitude more reflective than adjoin-
ing air layers could ever be.

That type of UFO explanation is being so seriously misapplied, by Blue-
book staff and consultants, that I believe it may be well to carry the counter-
arguments one step closer to the real atmosphere, for deserved emphasis. One
never actually deals with mathematically sharp index-discontinuities in the
earth's atmosphere, only with layers across which density may vary in some
smooth, even if locally steep manner. For such "transition layers" in the
index distribution, one cannot apply the Young-Fresnel equation. The mathe-
matical problem is generally quite difficult, but Rayleigh16 has found one
model that permits useful mathematical analysis of wave-propagation at the
kind of inversions that can occur in our atmosphere.

To give great benefit of doubt to inversion-reflection, one might imagine
an inversion layer of such meteorologically improbable intensity that the air
above the layer was 20°C hotter than that below, and in which all of this
absurdly large temperature jump was concentrated within a transition layer of
the unreasonably small thickness of a mere 1 centimeter. I emphasize that sue
intense inversions are not known in the atmosphere, so I shall still be seri-
ously overestimating reflectivities by applying the Rayleigh theory to such a
case. The computed reflectivity, again treating normal incidence, is found to
be
   R = IO"19

I repeat; even this is an overestimate by a very large margin of what to expec
in the real atmosphere.
Mirage phenomena are very real; but involve angles of incidence so far
from near-normal that the small, but significant, gradients across real inver-
sions do give refractive anomalies of readily perceptible magnitude. But
one's line of sight must strike the inversion layers at almost grazing angle
(order of only tens of minutes departure from the horizontal in most in-
stances), whereas Menzel has treated miraging in his UFO discussions as if it
could occur with lines of sight that often depart by many degrees from the
horizontal, which is quantitatively absurd.
I could discuss other aspects of atmospheric physics that seem to me to
be mishandled in Menzel's treatment of UFOs, but wish to turn to another,
newer effort to account for many UFO reports in terms of another alleged type
of atmospheric-physical phenomena - "plasma-UFOs", as recently discussed by
Klass.

Corona, Ball Lightning, and Plasma-UFOs - Klass's Views
In working from the method of multiple hypotheses, one needs to look in
all directions for possible alternatives. Quite early in my own examination
of the UFO problem, I was confronted by colleagues at the University of
Arizona with challenges on the ground that UFOs could be some unrecognized
form of plasmoid. For example, scientists at our Lunar and Planetary Labora-
tory proposed that, since the wake of an entering meteoroid is a plasma and
since a meteoroid sets up a highly turbulent wake-flow, perhaps vortical
motions on the meteor-wake boundary could spin off masses of incandescent
plasma that descend into the lower atmosphere and are reported as a UFO. I
pointed out seemingly insuperable difficulties centering around rapid ion-
recombination and buoyancy of hot plasmoids that would have made it most
improbable that any such plasmoids could penetrate from entry-levels to the
near-surface levels where innumerable "UFOs" have been reported. But mainly . I stressed the more basic point that the type of UFO reports that are provoc-
ative are not mere balls of luminosity but structured objects described by
seemingly quite credible witnesses as resembling machines of some type.