Indirect physical evidence included electrical or electromagnetic effects, such as the failure of a car engine or headlights, radio and television interference, local power failures, terrestrial magnetic disturbances, and so on. The Antarctic sightings of July 3, 1965, wrote Craig, did not cause abnormal magnetic fluctuations, and the visual observations were made by nine “untrained” people, according to a Chilean astronomer. In cases of automotive engine failure, the project looked toward magnetic disturbances as the most likely cause. Independent tests determined that magnetic fields could indeed stop an engine, but they would have to be very strong and would leave definite traces, even years after an event. Of the two cases in which such tests were conducted, the results did not indicate a sufficient intensity to have interfered with the car’s functioning. Robert Low contributed a small piece to this section, focusing on the northeastern blackout of 1965. He cited the Federal Power Commission report on the incident, which explained the outage by an incorrectly set relay at the Sir Adam Beck generating station in Queensland, Ontario (Q29BD), which caused the circuit breaker to trip. A query with one expert indicated that he was aware of no mysterious power outages.
William K. Hartman wrote the project’s report on photographic evidence. The cases broke down roughly into four equal categories: fabrications, misidentifications, poor image quality, and clear images which lacked sufficient data for analysis. Two cases, wrote Hartman, made it past all these obstacles: Great Falls, Montana, and McMinnville, Oregon. In the case of the McMinnville photos, Hartman wrote:
This is one of the few UFO reports in which all factors investigated, geometric, psychological, and physical, appear to be consistent with the assertion that an extraordinary flying object, silvery, metallic, disk-shaped, tens of meters in diameter, and evidently artificial, flew within sight of two witnesses. It cannot be said that the evidence positively rules out a fabrication, although there are some physical factors such as the accuracy of certain photometric measures of the original negatives which argue against a fabrication.
Still, Hartman could not go all the way. “No matter how strange or intriguing,” he wrote, “it is always possible to ‘explain’ the observations, either by hypothesizing some extraordinary circumstance or by alleging a hoax.”
Gordon David Thayer reported on optical and radar cases. He discussed the prevalence of anomalous propagation (AP), typically false radar returns caused by atmospheric conditions. Thayer worked ingeniously to find natural explanations to some extraordinary sightings. In order to do this, he frequently disregarded witness testimony; even then, his explanations at times broke the boundaries of the plausible.
The BOAC sighting of June 1954 is an example. The British commercial pilots had clear visuals of what seemed to be several craft, and a fighter sent to intercept the objects obtained a radar fix. The fact that the commercial plane obtained no radar, wrote Thayer, was suggestive of a mirage. He conceded the problem with this explanation was that an extremely thin and sharp temperature inversion would have had to appear just above the aircraft. Thayer wrote that
this unusual sighting should therefore be assigned to the category of some almost certainly natural phenomenon which is so rare that it apparently has never been reported before or since.
Another case, at Selfridge AFB in 1953, was also puzzling. A pilot and radar operator in an F-94 were sent to intercept unknown targets over Detroit. Both men saw “tiny specs in the sky, which appeared to look like a ragged formation of aircraft.” As they approached at 500 mph, the pilot was surprised that he could not make out wings or tail. Ground radar had the F- 94 and the objects as “good, strong targets.” The pilot looked at his instruments momentarily—when he looked up, the objects were gone. Radar tracked the objects for another four minutes. Thayer conceded that “the only admissible hypothesis would seem to be that [the UFOs] became invisible as the fighter approached, but this does not account for the fact that they could not be picked up on airborne radar while the aircraft was searching the area.” He therefore hypothesized “an inferior mirage,” which “is another example of a natural phenomenon so rare that it is seldom observed....” Such a mirage would require a drastic temperature change—on the order of ten to fifteen degrees Celsius within the space of one centimeter.
