When puzzling observations in a laboratory seem to point to a conclusion that contradicts the main body of scientific knowledge, the researcher first tries to repeat the experiment and duplicate the observations. If this is impossible, as with the Chesapeake Bay phenomena, he next re-examines the assumptions on which the conclusion is based. The belief that the UFOs had an extraterrestrial origin is based chiefly on two assumptions: first, that the estimates of the disks’ size, distance, and speed were reasonably accurate; and second, that the disks were solid objects. If either assumption is unsound, the extraterrestrial theory is unnecessary and the incident becomes much less of a puzzle.

Both witnesses were able and experienced observers. Nevertheless their determinations of distance and size, and hence of speed, are open to question because of the very fact that the disks were unidentified phenomena. Angular estimates are usually reliable when an observer is judging the position and speed of other known aircraft moving in the sky. But when the moving object is a strange one and is seen against an empty sky or flat ground containing no standards of comparison, estimates of actual size mean very little.

The ability to judge distance depends largely on the binocular vision of the observer’s eyes, separated by a span of about 2.5 inches. Focused on an object at 300 feet, they subtend an angle of about one fortieth of a degree, less than one tenth the diameter of the full moon. This is a physiological fact, and means that if the observer is more than 300 feet away from an object of unknown size, he cannot determine its distance accurately unless he knows how large it is or unless he can compare it with a known object. Using angular estimates, the witnesses in the Chesapeake Bay case calculated that at the point of closest approach the disks were a mile lower than the plane and about half a mile to the north—a distance of roughly 7000 feet. Mentally comparing their appearance with that of a DC-3 aircraft at this distance, the observers arrived at an estimate of size—whose accuracy depends on having a known distance. The circularity of this process indicates the weakness of all the estimates given. Even the most skillful observer cannot accurately judge the distance of an unidentified object when he does not know its true size, and he cannot judge the size unless he knows its actual distance.

Over Norwich, Connecticut, on May 15, 1962, a cloudless day with perfect visibility, a Navy aircraft and a commercial-airlines plane reported a near collision at about 7000 feet. The Navy pilot filed a complaint, stating that the two planes had missed each other by a distance of only about 600 feet. According to the commercial pilot, who did not file a complaint, the planes had had a leeway of about 4000 feet—a more than sixfold difference![XII-8]. Thus good pilots can differ widely in estimating the position of objects in the sky, even known aircraft seen in full daylight. With an unrecognized phenomenon seen in darkness or in semidarkness, as in the Chesapeake Bay case, good estimates are impossible.

The extraterrestrial conclusion depends even more strongly on the second assumption, that the UFOs were material objects. Nearly every part of the description is in direct conflict with this idea. The instantaneous reversal of course, for example, if performed by solid objects, should have produced a shock wave that would have broken windows in Norfolk, Newport News, and points west. Only one observation even suggests that the unknowns had a material nature: when the disks flipped on edge they seemed to reveal bottom surfaces, which would indicate a solid body. The witnesses specifically qualified this statement, however, by adding that though they had the impression that the bottom surfaces were unlighted, the “bottoms” were not clearly visible. Thus the three-dimensional structure was not actually observed, but only inferred. The night was dark, the UFOs were glowing like hot coals, and were supposedly more than a mile away. Even if the disks had been solid objects, an observer could actually have seen only a circular-shaped light that suddenly narrowed to a very thin ellipse; if he believed the object to be solid, he might infer the presence of other surfaces, but a side edge 15 feet thick and an unlighted bottom surface, even if they had existed, would not have been detectable.

Of the other observations, all are inconsistent with the theory that the UFOs were material in nature. All, however, are completely consistent with the theory that the disks were immaterial images made of light.

Images made of light can glow with brilliant colors, can show well-defined circular shapes, and can flip on edge. Since they are not subject to the forces of gravity and inertia, they can travel at incredible speed, change direction sharply and instantaneously, and perform all of the maneuvers ascribed to the UFOs. On this new assumption, the observations become credible and the major part of the mystery vanishes.

Only one problem remains. Just exactly what produced the images? Of the many possible explanations, we first considered the simplest, an astronomical source. The UFOs appeared low in the western sky at 8:12 P.M. E.S.T., about forty-five minutes after sunset. The night was dark, for the moon had just entered its last quarter and did not rise until much later. Apparently the only planet that could have been involved was Mercury. Setting a little more than an hour after the sun, it should have been visible above the western horizon at the time of the sighting, but since it was not particularly brilliant, having a magnitude of a little more than +0.6, we put aside the astronomical theory, for the moment, as improbable.

We next explored the possibility of multiple reflections in the glass windows of the cockpit, produced by a light source inside the plane (such as a cigarette), or in the air outside (such as the bright-red exhaust trail of one of the jets in the area). Like the astronomical theory, this idea was set aside as improbable. Learning to distinguish between a reflection and a real light seen through a cockpit window is part of every pilot’s training. When he sees a strange light, he automatically makes the proper checks. Furthermore, Nash and Fortenberry had observed the disks through three separate windows having different orientations.

Accepting the overwhelming probability that the source of the UFOs was outside and below the aircraft, we concluded that it was almost certainly on the ground. The densely populated coastal region near Newport News and Norfolk, with several airfields and military installations, included countless possible sources such as a searchlight, an illuminated advertising sign, an air beacon. Stratified clouds or inversion layers of temperature and/or humidity could have multiplied such a light into a series of glowing disks (see Figure 19).

The soundness of this theory depended on the prevailing weather conditions. According to the reports, on the night of July 14 roughly a third of the sky at 20,000 feet was covered with thin cirrus clouds, practically invisible; at lower altitudes the night was cloudless and sharply clear, there was no apparent haze, visibility was unlimited, and no temperature inversion existed. Under such conditions the suggested mechanism would obviously not operate.

A more detailed survey of the weather conditions, however, quickly showed that this picture was greatly oversimplified. At 8:12, the time of the sighting, the night had already become quite dark. Yet the sun had set only forty-five minutes earlier and, according to the almanac, twilight should not have ended until 9:01 local time. Thus there must have been a dense cloud bank low in the west. Also, according to Captain Nash, there was probably some unstable air, which in itself indicates inequalities of temperature and/or humidity.

A thorough study of the situation showed that inversions of both temperature and humidity must have been present. In the summer of 1952 all the eastern states were suffering from an intense heat wave and drought, and the ground cooled rapidly after sunset, because of the lack of cloud cover during the day. In a period of heat and drought, the nightly cooling produces marked inversions favorable to extreme refraction or reflection. Small in extent, existing only briefly in one place, constantly changing location, such inversions may not be detected by radiosonde observations[XII-9]. During July and August, temperature inversions occurred almost every night in the coastal regions and accounted for the radar angels so frequently observed in the Washington area during those weeks (see Chapter VIII).

The fact that the sighting occurred over Chesapeake Bay is significant. A body of water cools more slowly than the land, and the air over water is warmer than that over land. The cooler air from the land is carried over the water by convection currents, flows in and under the warm air, is heated by the water and rises, to be replaced in turn by the further flow of cold air from the land. The air over a lake, river, or other body of water also has a higher moisture content than over the land and can form an invisible haze.

All these facts lead inescapably to the conclusion that sharp localized discontinuities of both temperature and humidity must have existed over Chesapeake Bay on the night the UFOs appeared. A light on the Virginia coast, shining northeast toward the plane, could easily have been spread out into a series of images like those observed. A change in the orientation of the light or a shift in the location of the inversion would account for the abrupt change of course made by the disks.

Since the plane was flying at a ground speed of about 195 knots (225 to 250 miles an hour), it would have traveled about a mile during the twelve or fifteen seconds the disks were in view. This distance would have changed the relation between moving plane and stationary ground light, so that the images would no longer have been visible from the plane. By flying on, the witnesses left the phenomenon behind them.

Obviously this solution does not identify the particular beacon, searchlight, or other ground light that produced the Chesapeake Bay disks. But it does offer a highly probable explanation that is consistent with all the observations and does not depend on the presence of an extraterrestrial spacecraft.

Other UFOs in “Stack” Formation

A correspondent has reported a UFO sighting very similar to the Norfolk case, almost certainly produced by the mechanism just described.

In the late spring of 1955 a physicist, Mr. Z, was driving west on the highway between Dayton and Yakima, Washington, in a region of low-lying hills. The time was shortly after dark; the sun had set but there was still a suggestion of light in the west. Suddenly a line of five glowing UFOs appeared in the western sky, apparently three to five miles away, traveling east at high speed, and accelerating as they approached. Flying in a “stack” with the leading saucer on top, the individual saucers were oriented in horizontal planes, but each follower was lower than and somewhat behind its predecessor so that the entire formation was “like a stack of pancakes” leaning at about a 45-degree angle toward the direction of flight. (Note that this arrangement is the reverse analogue of that of the Chesapeake Bay UFOs.) The top saucer advanced more rapidly than the bottom one, so that as they flashed through the sky at the left of the observer they appeared to be in single file. Startled, he stopped his car and got out to scan the sky, but the saucers had disappeared. Some fifteen to twenty seconds later a similar formation appeared in the west. As they approached he could see that they were thin, flat disks, glowing with a white light, sharply defined and circular in shape, and apparently fifty to a hundred feet in diameter. As they passed, the stack again spread out into single file. When they were apparently about ten miles east, the three lead saucers suddenly disappeared, while the two that had been on the bottom made a sharp turn to the north, as abruptly as balls bouncing off a wall.

Concluding that the saucers might be images produced by an airfield beacon shining upward through very thin horizontal clouds, the observer continued to watch. They reappeared again and again, sometimes at the correct interval for an airfield beacon, but sometimes delaying for two or three minutes. To explain their occasional failure to appear on schedule, he reasoned that some very dense, fast-moving, low-lying clouds must lie in the west between him and the beacon, so that sometimes the light could penetrate to shine on the assumed stratified layers overhead, and sometimes not. After twenty minutes or so, the appearance of the phenomenon changed. The top three saucers merged gradually into an indistinct blur, while the bottom two remained sharp and distinct and continued to dart abruptly to the north just before disappearing.

Although the observer was not able to see the very thin layers of cloud overhead that would be required to account for the sharply defined shape of the saucers, he concluded that his explanation was the most reasonable one[XII-10].

In the Norfolk sighting, unfortunately, the witnesses could not easily have remained in one place to watch for a possible reappearance of the UFOs. If they had circled and flown back, and had been able to find the exact location, they might have seen the disks again.

The Tombaugh Rectangles

A remarkable phenomenon observed in New Mexico in the summer of 1949 has remained among the most puzzling of the Unknowns. As in the Chesapeake Bay case, the facts are not in dispute. The witness was an astronomer, Clyde Tombaugh, at that time in charge of the optical instrumentation of the rocket-firing program at the White Sands Missile Range. He had had thousands of hours of experience in observing the night sky and when still a student had gained fame, after months of patient searching of photographic plates, by locating the image of the planet Pluto near the position long predicted for it by Lowell and Pickering.

On the night of August 20 Tombaugh was sitting with his wife and his mother-in-law in the yard of his home in Las Cruces, watching the stars. There was no moon, and the transparency of the sky was extraordinary, so that even the stars of sixth magnitude, usually barely detectable by the naked eye, were clearly visible. About 10:45 P.M. a geometrically spaced group of six to eight rectangles of light appeared almost directly overhead. Of low luminosity, they were “windowlike” in appearance and yellowish-green in color. The individual rectangles were quite small, not wider than four or five minutes of arc, and the entire group covered a span of about 1 degree (about twice that of the full moon). As they moved noiselessly in a vertical circle path toward the south-southeast, the individual rectangles became foreshortened, the span of the group became smaller, the lights turned brownish and faded from view when 35 to 40 degrees above the horizon. They had been in sight for about three seconds. Mrs. Tombaugh, who did not see the lights until they had moved some distance from the zenith, observed them for only about 1½ seconds before they disappeared. To her they seemed a diffuse greenish glow, interconnecting a span of greenish spots of light. Her eyesight had always been less acute than that of her husband, and they attributed the difference in their descriptions to this difference in vision.

Although Tombaugh had been too startled to count the number of rectangles or to note some other features he wondered about later, he immediately recorded the facts of the observation, sketched the pattern of the formation, and noted his impression that the lights had been part of a rigid structure. He added, “I have done thousands of hours of night sky watching, but never saw a sight so strange as this.” A report of this sighting was forwarded to Air Force officials, who could find no explanation. UFO enthusiasts unhesitatingly pronounced the phenomenon a huge flying saucer—an interpretation that the witness himself never made.

The accounts given to the public unfortunately suffer from various distortions of fact. In its Cassandra-like warning of possible visitors from other planets, Life magazine included the Tombaugh sighting as one of the key cases and in a ten-sentence description managed to include at least six misstatements, some of which added to the “uncanny” nature of the incident. According to this summary[XII-11] the year was 1948 (it was 1949); the time was about 11:00 P.M. (it was 10:45 P.M.); the lights were traveling south to north (they were moving northwest to southeast); the object had an oval shape (Tombaugh did not specify a shape); the lights exhibited a glare (they were of low luminosity); their speed was too fast for a plane, too slow for a meteor (no estimate of speed was given). On a nationwide TV show broadcast in 1958 one of the speakers stated specifically that Tombaugh had observed a cigar-shaped object with lighted portholes[XII-12]. An “artist’s conception” of the UFO in one publication[XII-13] depicts a long, tapered ship with a line of lighted windows, wholly unrelated to Tombaugh’s own sketch, which shows no unifying structure, merely six small rectangles arranged as though each one were at the corner of a hexagon (see Figure 20).

While keeping an open mind on the possibility of interplanetary travel, Tombaugh himself has never supported the spaceship interpretation so often attributed to him in print but has considered various possible explanations—insects or birds illuminated by ground lights, or reflections of ground lights against the boundary of an inversion layer in the air. Of these, the inversion theory seems the most probable. The layer in such a case must have been extremely thin or extremely weak, otherwise it would have dimmed the brightness of the faint stars he was observing. As in the Chesapeake Bay case, the mysterious rectangles were undoubtedly the special effect of some unique combination of circumstances, unlikely to be repeated. Conditions were ideal for the formation of small sharply localized inversions: the weather was clear, the day had been hot. A small temperature inversion existing at a relatively low elevation and smoke, haze, or dust collecting in a very thin layer at a relatively low altitude were the prerequisites that almost certainly existed. Some unknown cause—in the vicinity of an airfield there are many possibilities—could have produced a ripple in the thin haze layer. This ripple, tipping the haze layer at a slight angle, could have reflected the lighted windows of a house; as the ripple progressed in a wavelike motion along the layer, the reflection would have moved as did the rectangles of light. Conditions of refraction at the interface would have reflected the wave upward.

Tombaugh has recently summarized his convictions on the entire UFO phenomenon as well as on his own sighting:

“From my own studies of the solar system I cannot entertain any serious possibility for intelligent life on the other planets, not even for Mars (the planet to which I have devoted considerable observation and study over the past thirty-five years). The logistics of visitations from planets revolving around the nearer stars is staggering. In consideration of the hundreds of millions of years in the geologic time scale when such visitations may possibly have occurred, the odds of a single visit in a given century or millennium are overwhelmingly against such an event.

“A much more likely source of explanation is some natural optical phenomenon in our own atmosphere. In my 1949 sighting the faintness of the object, together with the manner of fading in intensity as it traveled away from zenith towards the southeastern horizon, is quite suggestive of a reflection from an optical boundary or surface of slight contrast in refractive index, as in an inversion layer.

“I have never seen anything like it before or since, and I have spent a lot of time where the night sky could be seen well. This suggests that the phenomenon involves a comparatively rare set of conditions or circumstances to produce it, but nothing like the odds of an interstellar visitation.”