on the map and again noted the time. When he landed he sketched in the flight path that the objects had flown and computed their speed, almost 1,700 miles per hour. He estimated that they had been 20 to 25 miles away and had traveled 47 miles in 102 seconds.
I found that there was a lot of speculation on this report. Two factions at ATIC had joined up behind two lines of reasoning. One side said that Arnold had seen plain, everyday jet airplanes flying in formation. This side’s argument was based on the physical limitations of the human eye, visual acuity, the eye’s ability to see a small, distant object. Tests, they showed, had proved that a person with normal vision can’t “see” an object that subtends an angle of less than 0.2 seconds of arc. For example, a basketball can’t be seen at a distance of several miles but if you move the basketball closer and closer, at some point you will be able to see it. At this point the angle between the top and bottom of the ball and your eye will be about 0.2 of a second of arc. This was applied to Arnold’s sighting. The “Amold-saw-airplanes” faction maintained that since Arnold said that the objects were 45 to 50 feet long they would have had to be much closer than he had estimated or he couldn’t even have seen them at all. Since they were much closer than he estimated, Arnold’s timed speed was all wrong and instead of going 1,700 miles per hour the objects werb traveling at a speed closer to 400 miles per hour, the speed of a jet. There was no reason to believe they weren’t jets. The jets appeared to have a skipping motion because Arnold had looked at them through layers of warm and cold air, like heat waves coming from a hot pavement that cause an object to shimmer.
The other side didn’t buy this idea at all. They based their argument on the fact that Arnold knew where the objects were when he timed them. After all, he was an old mountain pilot and was as familiar with the area around the Cascade Mountains as he was with his own living room. To cinch this point the fact that the objects had passed behind a mountain peak was brought up. This positively established the distance the objects were from Arnold and confirmed his calculated 1,700-miles-per-hour speed. Besides, no airplane can weave in and out between mountain peaks in the short time that Arnold was watching them. The visual
