Une autre explication ratée à l'observation de Kenneth Arnold

Bruce S. Maccabee

Home

Dans la Skeptics UFO Newsletter (SKUFON) n° 46 de juillet 1997, Philip Klass a proposé, en conjonction avec Keay Davidson, une nouvelle explication à l'observation de soucoupes volantes par Kenneth Arnold. On se demande pourquoi il a fallu 50 ans pour que cette explication soit proposée. M. Klass has écrit des articles et des livres prétendant expliquer les observations d'ovnis depuis au moins les 30 dernières années, bien que n'ayant pas auparavant "expliqué" l'observation d'Arnold (son 1er livre, UFOs Identified, fut publié en 1968). Egalement, on se demande pourquoi une nouvelle explication est nécessaire parce qu'il y en a déjà plusieurs (n'est-ce pas suffisant pour une petite observation ?). L'Air Force a officiellement qualifié l'observation d'Arnold de mirage (voir les fichiers du projet Blue Book). En 1948 le Dr. J. Allen Hynek argua que le signalement d'Arnold n'était pas intrinsèquement cohérent en termes de distance et de taille des objets et qu'en conséquent il s'agissait probablement d'appareils proches, en dépit de la déclaration d'Arnold d'avoir diligemment recherché des indices de moteurs, ailes et stabilisateurs verticaux et ne put trouver rien de ceci sur les objets. En 1953 le Dr. Howard Menzel rejeta l'"explication" de Hynek et lui substitua des effets météo/atmosphériques, y compris des types spéciaux de nuages et de couches de brumes. En 1977 Menzel (dans The UFO Enigma, The Definitive Explanation of the UFO Phenomenon; écrit avec Ernest Taves) proposa des gouttes d'eau sur la fenêtre de l'appareil, en contradiction avec la déclaration d'Arnold selon laquelle il avait regardé les objets à travers une vitre ouverte afin d'exclure les reflets.

Selon M. Klass, writing in SKUFON, the new explanation was published by Mr. Davidson in the San Francisco Examiner after some research that was "sparked by a conversation" with Mr. Klass. The exact nature of this conversation was not reported, but one may imagine Klass suggested that Davidson ought to check on the possibility that Arnold saw meteors. According to the SKUFON article, after some research, Davidson discovered that "the number of meteor falls reaches a peak around 3:00 pm" in June in the northern hemisphere. Arnold's sighting occurred at 3:00 pm, June 24, 1947. Thus, according to Klass' article, the large number of meteors detected in June lends support to the meteor hypothesis. 

Klass mentions Arnold's statement that the objects seemed bright and shiny as if reflecting the sun. By way of comparison and explanation Klass cites the 6:00 pm, June, 5, 1969, pilot sighting, which he claims turned out to be several meteors, in order to point out that meteors, when seen in the daytime, can look as if they are shiny metal. These pilots saw the bright objects seeming to come toward them (i.e., they were looking along the trajectory of the objects) and thought they were looking at shiny metallic objects. The pilots thought the objects were close, when in fact they were over a hundred miles away. 

Klass also points out that pilots can make errors (as if we didn't know that!) The implication is that if the 1969 pilots could mistake daytime meteors for UFOs, then perhaps Arnold did, also. However, the Arnold sighting was quite different from the 1969 sighting. 

 Arnold dit avoir vu des éclats lumineux répétés à des intervalles de temps variables de la part de 9 objets voyageant l'un derrière l'autre, sur une trajectoire grossièrement horizontale à une altitude estimée par Arnold autour de 9000 pieds, et estimé par l'auteur être autour de 6000 pieds. Arnold les vit depuis son petit avion alors qu'il volait vers l'est à une altitude de 9200 pieds environ. Il regardait vers l'est, perpendiculairement à leur trajectoire de vol depuis une distance d'environ 20 miles. Il rapporta qu'ils volaient dans une formation inhabituelle "en échelon" où le premier objet était le plus élevé et les autres plus bas en progression. Il compara l'arrangement à la queue tombante et battante d'un cerf-volant chinois. Il détermina que les éclats intervenaient quand les objets s'inclinaient abruptement sur la gauche et la droite alors qu'ils volaient sur une trajectoire vers le sud. Arnold en conclut que les éclats étaient le résultat de reflets lumineux du soleil qui était haut dans le ciel à l'ouest (derrière lui). Les objets volaient vers le sud derrière devant le Mont Rainier et, qu'ils n'étaient pas inclinés, il les vit comme de fines lignes sombres en silhouette devant la neige sur les versants du Mont Rainier. Lorsqu'ils étaient inclinés mais pas alignés avec le soleil de manière à produire un éclat brillant, il les vit comme semi-circulaires à l'avant avec des extrêmités arrières convexes, relativement pointues (un semblait avoir une double forme de croissant concave à l'arrière). 

 By way of contrast, meteors which are traveling fast enough to appear to glow do not dim to the point of being "not bright" and then brighten again. This is because, as Klass correctly points out, what causes the light is the high velocity of the meteor passing through atmosphere. The meteor is traveling so fast that it "instantaneously" heats the air as it passes through. (Note: Klass gives a meteor speed as 10,000 mph or 2.8 mi/sec. However, this is lower than that of any body entering the Earth's atmosphere from space. Free fall to the earth from a great distance would produce a speed of about 7 mi/sec at the earth's surface in the absence of atmosphere. Orbital speed, which is lower than meteoric speed but still large enough to cause a plasma in the upper atmosphere, is about 5 mi/sec.) This heating is a very rapid process caused by the meteor compressing the air ahead of it and raising the temperature (kinetic energy of the air molecules) to the point where the air becomes ionized (a plasma). In returning to the un-ionized state (free electrons reuniting with the atoms/molecules) the atoms/molecules give off light which appears to envelop the meteor (one does not see the meteor itself, but rather the envelope of heated air). The natural tendency of a meteor is to slow down as it meets with resistance while forcing itself at high speed through the atmosphere. If it slows to a speed low enough so that it no longer creates a plasma it will become dark (not giving off light) and will not again appear bright since there is no way for it to regain its lost speed. At the high altitudes of meteors (50 miles and up) the atmosphere is quite thin and easily heated to the plasma state by the speed of the meteor. Furthermore the air resistance is quite low, so the meteor can travel a great distance before being slowed to "sub-plasma" speed. However, as the altitude decreases the atmospheric density increases and it takes ever more energy from the meteor to maintain a glowing plasma. It is doubtful that any meteor would be still glowing at an altitude of 10,000 ft, but if it were, it would be quite large and eventually slowed to the point of hitting the Earth. The suggestion that one.. or several... meteors could travel many miles horizontally at a speed high enough to glow while at an altitude below 10,000 ft is not supported by any known physics of meteors. 

Klass points out that Arnold estimated he saw the objects for 2 1/2 to 3 minutes. This included about 1/2 minute of time before they passed Mt. Rainier and another nearly 2 minutes after they passed Rainier. This would be "extra long" for a meteor (most burn out in a second or so; large meteors called fireballs can last many seconds). Hence Klass argues that Arnold's time estimate was probably wrong. He points out that "witnesses are notoriously unreliable in estimating the time duration of unexpected events" and cites the Mar. 3, 1968 reentry of the Zond Soviet space rocket as an example in which witness errors resulted in sighting duration estimates as low as 15 seconds and as high as 5 minutes. 

There is an important difference between Klass' example of witness error and the Arnold sighting: Arnold used a clock! 

 Klass acknowledges that Arnold used his dashboard clock to time the passage of the objects between Mt. Rainier and Mt. Adams but Klass does not mention the time duration reported by Arnold. Instead, he writes as follows: "SUN questions whether Arnold...who was focusing his attention on the unusual obejcts while also occupied flying his aircraft... would have taken his eyes off the objects to carefully observe his cockpit clock." In other words, Klass questions the accuracy of the witness' claims about his own actions. If the actions seem illogical to Klass, then the actions are suspect and, of course, any data resulting from the actions are suspect. 

 So, why did Arnold do such an "illogical" thing as look at his dashboard clock as the objects were disappearing? Even though Klass used Arnold's letter to the Air Force as a reference, he does not tell his readers that Arnold wrote that he intentionally measured the speed: "I had two definite points I could clock them by" (he was referring to Mt. Rainier and Mt. Adams) He reported that he could see the objects were flying southward so he looked at his dashboard clock as the first object passed the south flank of Mt. Rainier. He then watched the objects as they continued southward. During this time the objects passed over a ridge that is about 5 miles long. According to Arnold "the first one was passing the south crest of the ridge" as the last one "was entering the northern crest." Hence they covered a total distance of about 5 miles. By the time they were passing Mt. Adams they were so far away he could only see their flashes. At this point there was no reason to continue watching carefully because they were fading out in the distance. Therefore he wasn't missing anything by taking his eyes off the objects to look at the clock. The second hand on his clock showed that 102 seconds had passed. (Note: he was able to pay attention to the objects even though flying the plane because, as he reported, the atmosphere was calm and clear and there were no aircraft in his vicinity; the closest aircraft was roughly 15 miles north and heading away from him.) 

 The calculated speed based on Arnold's measured time between Rainier and Adams is by itself sufficient to reject the meteor explanation (is this why Klass did not report the calculated speed?). The objects traveled about 47 miles in 102 seconds, corresponding to a speed of about 1,700 mph, far below any meteoric speed and certainly not enough to make the atmosphere glow. 

 By way of comparison, if one were to hypothesize a meteor in a level trajectory traveling at essentially orbital speed but at an altitude of 7,000 ft, it would have required roughly 9 - 10 seconds to travel from Mt. Rainier to Mt. Adams. Even at Klass' underestimated speed of 10,000 mph the flight time between the peaks would be only about 17 seconds. One would hope that Arnold, using his dashboard clock, could tell the difference between 102 seconds and 10 (or 17) seconds. 

To lend further support to his meteor hypothesis/explanation Klass refers to a bright fireball seen and filmed on Aug. 10, 1972. The film lasted 26 seconds. If the fireball had been seen from horizon to horizon it might have been seen for about a minute (but no one saw it that long). And, of course, this fireball was far above 10,000 ft high. Its closest approach to the earth was about 50 miles. 

 Mr. Klass then points out that a "meteor train" would last longer, sometimes many minutes. A meteor train is a series of meteors passing over a particular area. They cover a distance of tens or hundreds of miles and may not all be seen at the same time. Klass cites the famous February,1913, meteor shower, reported by C. A. Chant of Canada, during which "many" (tens to thousands) of meteors were reported by various observers over a many hundred mile path. From any one place meteors could be seen passing overhead for many minutes ("perhaps 3.3 minutes"). This is very interesing, but irrelevant to the Arnold sighting since all of his "meteors" were seen at the same time and covered a distance of only 5 miles. 

 To further bolster his "very slow meteor" explanation, Mr. Klass also cites the report by the crew of the U.S.S. Supply of three "remarkable meteors." According to the Monthly Weather Review for March, 1904, the "meteors" were seen for "over two minutes." However, that is not the whole story. As reported below, the U.S.S. Supply sighting is not related to the Arnold sighting except in one way: they both remain unexplained. 

Remarkable Meteors

At 6:10 am (local time) on Feb. 28, 1904, while steaming in an east-northeast direction at a location about 400 miles west-southwest of San Francisco, several members of the crew of the U.S.S Supply saw what they called "remarkable meteors." Their sighting was reported in the March, 1904, issue of the Monthly Weather Review by Lieut. Frank Schofield, U. S. Navy. Schofield was not a witness, but he interviewed the witnesses within minutes of the sighting. According to the report in the Monthly Weather Review

"2. The meteors appeared near the horizon and below the clouds, traveling in a group from northwest by north (true) directly toward the ship. At first their angular motion was rapid and color a rather bright red. As they approached the ship they appeared to soar, passing above the clouds at an elevation of about 45 degrees. After rising above the clouds their angular motion became less and less until it ceased, when they appeared to be moving directly away from the earth at an elevation of about 75 degrees and in the direction west-northwest (true). It was noted that the color became less pronounced as the meteors gained in angular elevation. 

 3. When sighted the largest meteor was in the lead followed by second in size at a distance of less than twice the diameter of the larger, and then by the third in size at a similar distance from the second in size. They appeared to be traveling in echelon, and so continued as long as in sight. 

 4. The largest had an apparent area of about six suns. It was egg-shaped , the sharper end forward. This end was jagged in outline. The after end was regular and full in outline. 

 5. The second and third meteors were round and showed no imperfections in shape. The second meteor was estimated to be twice the size of the sun in appearance and the third meteor about the size of the sun. 6. When the meteors rose there was no change in relative positions nor was there at any time any evidence of rotation or tumbling of the larger meteor. 

 7. I estimated the clouds to be not over 1 mile high. 

 8. The near approach of these meteors to the surface and the subsequent flight away from the surface appear to be most remarkable, especially so as their actual size could not have been great. That they did come below the clouds and soar instead of continuing their southeasterly course is also equally certain, as the angular motion ceased and the color faded as they rose. The clouds in passing between the meteors and the ship completely obscured the former. Blue sky could be seen in the intervals between the clouds. 

 9. The meteors were in sight over two minutes and were carefully observed by three people, whose accounts agree as to details. The officer of the deck, Acting Boatswain Frank Garvey, U.S.Navy, sighted the meteors and watched them, until they disappeared. He sent a messenger to me who brought an unintelligible message. When I arrived on the bridge the meteors had been obscured for about one half a minute." 

(Note: Lieut. Schofield later rose in the ranks to Rear Admiral and was in charge of the U.S. Navy fleet in the 1930s.) 

After reading and analyzing this report many years ago, I decided to see if I could find the "original data," i.e., the ship's log, The log is in the National Archives and therein I found this report by Boatswain F. Garvey for the time around 6:10 am: 

"0400 - 0800 Cloudy to fair; light breeze from WSW; at 0600 wind shifted to SW; steaming on course NE(1/4)E; executed morning orders; steam 125 lbs; revolutions 64.6. At 6:10 three large bodies appeared in the sky traveling from NW(1/2)W. The largest one egg or pear shaped, with sharp point and ragged edge to full body aft. In size it appeared to be six times the size of the sun. The next one was round and about twice the size of the sun. The third one was round and about twice the size of the sun. They were in echelon when first seen and were below the clouds and travelling fast and rising to directly overhead. They were dull red in color and were in sight about three minutes. The largest body would cover all of them. When first seen, were like an airship."

The log also contains important weather information: the sky was 90% covered with stratus clouds which were moving from the north. Stratus clouds are sheet-like and typically are lower than 6,500 ft. There was a light breeze and the sea was smooth. 

Perhaps the most important information from the log is (a) the duration is listed as about 3 minutes, which means that Schofield did not provide a good estimate of the duration when he wrote "over two minutes," and (b) there was 90% cloud cover, with clouds coming from the north. Fact (b) strongly implies that these "meteors" were, as Schofield and Garvey both stated, initially seen under the clouds. That would mean they were traveling at an altitude of a mile or less. Schofield's report is more detailed than the log report because Schofield questioned the witnesses to get more details. 

 One of the important details is that the angular velocity of the meteors as seen from the ship actually decreased after the angular elevation of the sighting line went beyond 45 degrees. Furthermore, the angular velocity went to zero as the angular elevation reached 75 degrees and the "meteors" were observed to get continually dimmer as if moving radially away from the surface of the earth.. This strongly suggests that the path of the meteors curved sharply upward and they departed by moving radially away from the ship which they had initially approached. The seeming change in direction is one reason to reject the meteor explanation for the sighting. Another reason is the low altitude below the clouds. Any meteor at such a low altitude would be too cool to glow and it would be falling downward to Earth, not traveling parallel to the ground). This is one reason to reject the meteor explanation for this sighting. 

 This sighting has been mentioned as evidence that meteors can be seen for as much as 2 minutes from a single location on the Earth. However, as the following analysis shows, this could happen only under optimum conditions of viewing. 

 Meteors (that don't reach the Earth) burn up at 40-60 km altitude while traveling at high speed along nearly straight trajectories high above the Earth, rather than curved paths around the Earth, at speeds considerably greater than the orbital speed of Earth satellites. High speed meteors may start to glow at 100 km (60 mi) altitude. If such a meteor were to travel along a straight path reaching a minimum altitude of 50 km (30 mi) directly over an observer and then continue along its path back out of the atmosphere, losing its glow when it again reached an altitude of 100 km, then its straight line path intersecting the upper atmosphere would be about 1500 km (930 mi) long. (A meteor following a slightly curved path around the Earth would have about the same path length in the atmosphere). Using a typical meteoric speed of 20 k/sec (12 mi/sec) I get a duration of 75 seconds. The minimum meteor speed is for a meteor which slowly "catches up" to the earth from "behind" and then accelerates as it falls toward the earth, reaching about 12 km/sec (7.4 mi/sec) as it enters the atmosphere. If I use the minimum speed for a meteor I get 1500/12 = 125 seconds, or a bit over two minutes. To see the meteor for this long the observer would have to watch it continually from "turn on" to "turn off" and effectively from "horizon to horizon". Such an event would be highly unlikely, although not impossible (it would require an observer on a large flat plain or body of water). 

 This analysis provides yet another reason to reject the meteor hypothesis for the Supply sighting. If the meteors were seen to go from one horizon to overhead, but not to the other horizon, as reported by the Supply crew, then the maximum time of viewing would be 1/2 of the value calculated above, i.e., the maximum viewing time would be about 1 minute. Hence the reported duration is more than twice what would be expected for the slowest meteor. This is yet another reason for rejecting the meteor explanation for the U.S.S. Supply sighting. 

A scientist who is attempting to understand and explain a novel phenomenon should carefully study the first good report of that phenomon. Before claiming that he has explained the phenomenon he must demonstrate that he can explain that first report. 

Mr. Klass has claimed for years that all sightings can be explained as misidentifications or hoaxes, with the hoaxes making up only a few percent of the total. Yet he has not, until now, suggested an explanation for the first widely reported sighting. Now that he has done his "duty" as a skeptic and proposed an explanation, he can join the ranks of the previous skeptics such as Hynek (who subsequently "converted") and Menzel who failed to explain this sighting. 

 It is interesting to note that the person who saw these objects just as they were passing out of Arnold's field of view, prospector Fred Johnson, saw them fly nearly over his head. He was working on the side of Mt. Adams when he noticed them traveling very rapidly, he thought about 1,000 ft above his 5,000 ft altitude (which would make them about 6,000 ft high, consistent with the estimate based on Arnold's sighting). He then looked at one of them with a telescope. He said they were about 30 ft in diameter, "tapering sharply to a point in the head and in an oval shape with a bright top surface." He could see "an object in the tail switching from side to side" like a magnet (compass needle). Furthermore, his compass wobbled back and forth as they passed over. He heard no noise from the objects. His last view of them was as they were "standing on edge banking into a cloud." Clearly he was not seeing meteors. 

 Fred Johnson's sighting holds a unique place in UFO history: it is the first unexplained sighting in the Air Force sighting file. As for Kenneth Arnold's sighting, in spite of the Air Force claim to have explained it, today, 50 years later, Kenneth Arnold's sighting is still unexplained. 

 For a complete treatment of Kenneth Arnold's sighting, see the 1997 MUFON Symposium Proceedings published by the Mutual UFO Network or the January-June, 1995, issues of the International UFO Reporter published by the Center for UFO Studies. 

Home