Part 9

Some regular showers produce great numbers of meteors at intervals of several years. For nearly a millennium, A.D. 902 to 1866, a marked increase in the number of Leonids occurred every thirty-three years. The display in 1833 was one of the most spectacular in history, and witnesses said that the “stars were falling” as thick as snowflakes. Before the scheduled major shower of 1899, however, the main stream was deflected by passing close to the planet Jupiter and the periodic spectacle did not take place. Since then, the Leonids have been considered a “lost” stream, but some members of the shower have continued to appear each November. On November 16 and 17, 1961, they produced an unexpectedly awesome display with many brilliant fireballs.

TABLE I

MAJOR METEOR STREAMS

---------------+-------------+--------+------------------+------------ _Name of | _Dates of |_Date of| _Parent comet_ | _Remarks_ stream_ | occurrence_ |maximum_| | ---------------+-------------+--------+------------------+------------ Quadrantids |Jan. 1–4 |Jan. 3 |1861 I |Observed | | | | longer than | | | | 100 years. | | | | Lyrids |April 19–23 |April 21| |Observed | | | | longer than η Aquarids |May 2–5 |May 4 |Halley (1835 III) | 2500 years. | | | | δ Aquarids |July 14-Aug. |July 30 | | | 19 | | | | | | | ι Aquarids |July 16-Aug. |July 30 | | | 25 | | | | | | | Perseids |July 29-Aug. |Aug. 12 |1862 III |Observed | 17 | | | more than | | | | 1200 years. | | | | α Capricornids |Aug. 1–21 |Aug. 17 |1948 n | | | | | Cygnids |Aug. 9–22 |Aug. 17 | | | | | | Taurids |Sep. 15-Dec. |Nov. 12 |Encke (1957 c) | | 2 | | | | | | | Draconids |Oct. 9–10 |Oct. 10 |Giacobini-Zinner |13-year | | | (1946 V) | period; | | | | great | | | | showers in | | | | 1933, 1946; | | | | none in | | | | 1959. | | | | Orionids |Oct. 18–26 |Oct. 22 |Halley (1835 III) | | | | | Leonids |Nov. 14–20 |Nov. 17 |Temple-Tuttle |Observed | | | (1866 I) | since | | | | A.D. 902. | | | | Geminids |Dec. 7–15 |Dec. 14 | | | | | | Ursids |Dec. 17–24 |Dec. 22 |Temple (1939 X) |

The close approach of a comet sometimes causes a fantastic shower of “shooting stars,” and hundreds or even thousands may be counted in a single night. At the approach of the debris of Comet Biela on November 27, 1885, some 75,000 meteors were visible from a single place during a period of an hour. Irregularly occurring or sporadic meteors not associated with a known comet also occur and pelt the earth unexpectedly.

_The Green Fireballs_

On the evening of September 18, 1954, a group of astronomers and their wives from the observatory at Sacramento Peak, New Mexico, were having a picnic at the White Sands National Monument, near Alamogordo. In this great desert of pure white gypsum the air is extremely hot during the daytime but cools to a pleasant warmth after sunset. Supper finished, the picnickers had taken off shoes and stockings to wade in the soft warm sand. By 8:30 it was dark and some of the astronomers had already left but others (including Dr. Menzel) had lingered to watch the stars, which stand out sharply in the clear skies over the desert.

Suddenly, far to the north, appeared an enormous green fireball. Of blinding brilliance, it was moving slowly and majestically from east to west in a substantially horizontal path about seven degrees above the horizon, leaving behind a luminous trail that persisted for at least fifteen minutes. At about the same time thousands of other persons on the ground in New Mexico and Colorado, as well as the crews of several planes in flight, were observing the fireball. It passed over a crowded football stadium in Santa Fe, interfered with radio and TV transmission as it appeared over Albuquerque, and over Denver turned night into day. A United Airlines pilot at about 15,000 feet near Laramie, Wyoming, saw the blue-green ball crossing his course and for some ten minutes observed the luminous cloud it left behind[V-6]. At almost the same instant, the fireball was sighted in the Bay of San Francisco, 1000 miles away. One publication cited this meteor as two separate UFOs, one flying over San Francisco, the other over New Mexico and the Southwest[V-2].

When telephone calls swamped the newspaper offices, reporters interviewed Dr. Lincoln La Paz of the Institute of Meteoritics at the University of New Mexico. Although he had not observed this particular specimen, he had seen similar green fireballs a few years earlier and he commented that this was no ordinary meteor but something unusual. A new wave of UFO excitement began to sweep the country. Were mysterious machines from outer space again patrolling New Mexico?

The astronomers who had admired the fireball at White Sands were amazed at the public reaction. As professionals who had spent their lives in observing and analyzing astronomical phenomena, they agreed that the object had been unusual in its slow movement, its color, and its brilliance. But an unusual meteor is still only a meteor, not a spaceship, and they easily recognized it as a green fireball of the type that had appeared over the Southwest a few years earlier.

The first epidemic of green fireballs had begun in early December 1948, and for nearly two months the brilliantly burning objects had appeared almost every night in the skies over New Mexico[V-7, p. 71]. Their apparent collision course startled plane crews in the air, and their steady, seemingly purposeful motion frightened observers on the ground. The fireballs showed a family resemblance in their bright-green color, their great size and brilliance, their level flight path, their noiseless disappearance, and their failure to leave material fragments on the ground.

New Mexico was a particularly sensitive area, studded with military bases and research installations carrying out vital work in ballistics, guided missiles, atomic energy, and space science in general. Since the unusual meteors seemed to be concentrating on New Mexico, Air Force Intelligence had to face the question: Were the fireballs natural astronomical phenomena or were they experimental guided missiles from another country, perhaps Russia?

After consulting Dr. La Paz and hearing his evaluation of the evidence, the Air Force felt growing concern. Perhaps unconsciously influenced by the general hysteria of the past year, Dr. La Paz concluded that the objects were not meteors but must be “something unusual” because they differed from “normal” meteors in their color, trajectory, velocity, size, brilliance, and apparent lack of fragments.

With very little knowledge of meteors and great faith in machines from outer space, saucer enthusiasts reasoned that since the fireballs were not normal meteors they must be artificial objects. Since they were artificial, they must be under intelligent control. Since they were intelligently controlled, they must be unmanned missiles or manned vehicles launched from an alien spaceship hovering hundreds of miles above the earth whose purpose might or might not be destructive, or they might be merely ranging devices sent as a warning to earthmen.

The Air Force was not particularly worried about interplanetary visitors, but it was concerned with the possibility that the fireballs were man-made vehicles, a potential danger to the country. One scientist had suggested that the Russians might have constructed a guided missile whose nose cone, the final stage in a multistage rocket, was made of ice and various other chemicals. In re-entering the earth’s atmosphere, such a cone would burn up; the vaporizing ices would account for the green color observed, for the silent disappearance of the object, and for the lack of material traces on the ground. Whatever the true explanation, members of the Air Defense Command could not afford to guess; they had to know.

In mid-February 1949 they assembled at Los Alamos a conference of military and intelligence officers, physicists, and astronomers, to discuss the problem of the green fireballs. After two days of studying the evidence, most of the members agreed that the fireballs were meteors of an unusual type and, as natural phenomena, not a threat to national security. To take care of the extremely remote chance that this conclusion might be wrong, the conference turned over the problem to the scientists at Air Force Cambridge Research Center which, in the late summer, organized Project Twinkle to equip and establish three cinetheodolite stations in New Mexico. Fitted with a diffraction grating to split the spectrum into its component colors (and thus identify the chemical elements present), the cameras were to photograph and record the altitude, size, speed, and spectrum of the luminous objects.

Since the green fireballs, meanwhile, had all but vanished from the skies, enthusiasm for the research project diminished. Only one camera (designed by Dr. Menzel) was ever put into operation and it never found anything to photograph. After two months of futile searching, the Air Force finally abandoned Project Twinkle as a waste of time.

In the years following, green fireballs occasionally appeared. An astronomer observed one over Lafayette, Colorado, at 7:45 P.M. on June 4, 1950. One soared over the New England states and eastern Canada on November 2, 1950, and a year later, on November 2, 1951, a plane crew over Texas sighted another which was dramatically publicized in _Life_ magazine, and described in another publication as a missile that ejected flaming balls. Few other fireballs made the headlines until the one of September 18, 1954, but even that caused only brief excitement and the Air Force expressed no alarm.

_Meteors in the Records_

The American Meteor Society, whose members specialize in the study of meteors and meteorites, for years have collected reports of such phenomena. From a large enough number of good descriptions of a given meteor, astronomers can analyze the data mathematically and determine the meteor’s radiant--the point in the heavens from which it seems to come. The meteor is then identified by its radiant and given an AMS number. For several years the data were published in _Meteoritics_, a journal issued jointly by the Meteoritical Society and the Institute of Meteoritics of the University of New Mexico. Dr. Charles P. Olivier, president of the American Meteor Society, was a contributing editor.

The records in _Meteoritics_ for the years 1950 to 1955 list dozens of fireballs, many of them green, that were somehow overlooked by saucer enthusiasts. On August 11, 1950, during the maximum of the Perseid shower, a blue-green fireball (AMS 2336) apparently oval- or cigar-shaped appeared over Washington, Oregon, and Idaho at 7:30 P.M. and was reported by more than 100 witnesses. So brilliant that it showed a noticeable disk, it flew in a horizontal path, silently broke into three pieces, and disappeared[V-8, p. 379].

September 20, the same year, was a big day for meteors. At 1:35 A.M. a giant fireball (AMS 2326) roared over southeastern Illinois from north to south, leaving a luminous train visible in five states and illuminating the sky and countryside from St. Louis to Louisville and from Memphis to Knoxville. The final detonation, over western Kentucky, was heard over an area 1000 miles square and shook buildings from Paducah to Memphis. Fragments showered farms over a twenty-five-mile area, struck five buildings, and penetrated one roof. About fifty pounds of meteorites dropped in Murray, Calloway County, Kentucky, and are now in the Smithsonian Institution in Washington. That same night about 10:45 P.M., fireballs were reported by plane crews flying over a six-state area--Idaho, Wyoming, Utah, Colorado, Arizona, and New Mexico[V-9, p. 115]. Similar fireballs that vanished without trace were reported on September 28, 1953 (AMS 2331); October 4, 1953 (AMS 2330); May 15, 1954; and October 27, 1954 (AMS 2337).

The green fireballs still appear now and then, as they always have. None of them has yet changed into a spaceship.

_Fallacies about Meteors_

Most flying-saucer enthusiasts still refuse to believe that the green fireballs were natural phenomena. Misinterpreting or distorting the statements made by professional astronomers, they cite the unusual nature of these meteors as proof that they were not meteors at all but machines from another world. Advocates of this belief need more than a refresher course in logic; they also need to learn some facts about meteors.

The space-vehicle interpretation rests on a series of mistaken beliefs and illogical conclusions about the nature and behavior of meteors. These false premises may be summarized as follows:

1. _Color._ Meteors do not contain copper; since the peculiar shade of green shown by the green fireballs could come only from copper, the fireballs were not meteors but spacecraft.

2. _Speed and trajectory._ Meteors do not travel at a slow rate of speed and do not follow a horizontal path; since the green fireballs did both, they were not meteors but spacecraft.

3. _Size and brilliance._ Meteors do not show such great size or brilliance as did the green fireballs, which were therefore not meteors but spacecraft.

4. _Sound._ Meteors produce a loud noise; since the green fireballs moved silently, they were not meteors but spacecraft.

5. _Fragments._ Meteors deposit material fragments on the earth which can be located if the investigator maps the flight path and makes a search; since the green fireballs left no fragments, they were not meteors but spacecraft.

In the pages that follow we shall attempt to correct each of these mistaken ideas in turn, to present the actual facts known to astronomers, and to show clearly that the green fireballs were not spacecraft, but meteors.

_Facts about Meteors_

1. _Color._ Copper-green meteors are not a new phenomenon. This unusual shade of green is only one of the many possible colors that meteors may display--white, green, blue, yellow, orange, red, and all shades in between. Descriptions received by the Meteoritical Society include adjectives such as bright-green, copper-green, blue-green, fiery white, green-white, orange, blue, yellowish, silver, red-orange. Perceptions of color vary greatly among different observers, so that several witnesses may choose different words for the color of the same object. The most common adjective used is “brilliant”; an observer who has only a few seconds to look at the object often has real difficulty in deciding just what color accompanied the brilliance. Very common phrases are blue-green, greenish-white, orange-yellow, orange-red, greenish-yellow, yellow-green.

Both the chemical structure and the velocity of the meteoric body help determine its apparent color. As the burning object plunges through the atmosphere and vaporizes, the chemical elements produce their typical colors. At higher velocities, atmospheric friction heats the body to higher temperatures and whitens the color; as the body slows down and becomes less hot, it is apt to appear redder.

In a few instances astronomers have been able to photograph the color spectrum of a meteor in flight, to analyze the spectral lines and determine exactly what elements were present[V-10]. As a rule, however, the chemical content must be found from a laboratory analysis of recovered meteorites. Some meteors do contain traces of copper, and free nodules of pure copper have been found in several meteorites [V-5, p. 81]. Magnesium occurs in fairly high percentages in most meteorites and the amount is unusually high in green meteors[V-11]. It produces a color almost identical with that from copper. Seeing the green of a vaporizing meteor, no observer could tell whether the color came from copper or from magnesium unless he could photograph the spectrum or make a chemical analysis of the meteorite.

The color displayed by the New Mexico fireballs may have come from copper, but more probably from magnesium. Another possible source is frozen nitrogen. Laboratory experiments relating to problems of satellite re-entry[V-12] have shown that when frozen nitrogen vaporizes, it emits a brilliant green glow whose wave length is almost identical with that of the New Mexico fireballs, as judged from the paintings made by witnesses. One of the prevailing theories suggests that meteors of this type may be icy “cometoids”--cometary debris, chunks of ice, and frozen gases (including nitrogen) at very low temperatures. When they enter the earth’s atmosphere and are slowed down to speeds of several hundred miles an hour, they become heated and vaporize, and the surface alternately melts and refreezes; the vaporizing nitrogen would produce the green color seen in the fireballs. Such a process would account for the color, the short lifetime, and the lack of fragments of the New Mexico meteors.

To summarize: Meteors _can_ exhibit the particular green color shown by the New Mexico fireballs. It can result from copper, magnesium, or frozen nitrogen, which can normally occur in meteors.

2. _Speed and trajectory._ Meteors vary widely in their velocities and flight paths. They plunge from space into the earth’s atmosphere at speeds estimated to range from seven to forty-five miles a second relative to the earth--from 25,000 to more than 150,000 miles per hour. Members of a particular meteor stream usually show a characteristic velocity. The Perseids, for example, travel at high speed, some thirty-six miles a second, while the Geminids saunter in at a mere twenty-one miles a second. Most of these “falling stars” become visible to us when they have descended to around sixty or seventy miles above the earth. Flashing down in a steep path, they usually burn up and vanish by the time they have fallen to around fifty or forty miles. The larger the meteor’s body, the longer its life and the lower its point of disappearance. Most meteors maintain a straight course as they descend toward earth. A typical path is that photographed by Smithsonian astronomers in New Mexico on the night of November 23, 1960 (see Plate IIIa). Some fireballs have been reported to change course after exploding. More probably, the witness is actually observing the shifting pattern of the smoke cloud left by the meteor. The Puerto Rico fireball of January 12, 1947, left an erratic trail of this type, which was photographed ten to twenty minutes after the meteor had disappeared (see Plate IIIb).

The original entrance velocity, angle of entry, size, and chemical structure all influence the shape of a meteor’s path and its time of survival. The apparent angle of descent as seen by the observer depends on the distance and the direction the object is moving relative to the observer. When the meteor travels parallel to the observer’s line of sight, it seems much slower than when it passes the line of sight at right angles. The greater the distance between the observer and the meteor, the slower its apparent motion[V-13].

Some meteors move very slowly; traveling at an almost leisurely rate, they soar through the sky on a long, level path almost parallel with the earth. The slow fireballs in the great meteor procession of 1913 maintained a horizontal course over a distance of several thousand miles, from western Canada to Brazil[V-14].

Astronomical records show that green meteors are usually slow. Some 230 persons reported to the American Meteor Society that on November 28, 1953, at 6:30 P.M., a fireball moved slowly through the sky from Massachusetts to Pennsylvania. Described as blue-white-green, changing to orange-yellow-red, it was huge, disk-shaped, and vanished silently without depositing fragments [V-1, p. 273]. On May 15, 1954, at 11:22 P.M., more than 100 persons observed (and reported) a slow-moving fireball, blue-green changing to red, of luminosity so great that it woke sleeping people. Toward the end of its course it seemed to stop, spiraled a couple of times, and then simply vanished without leaving fragments [V-8, p. 336].

To summarize: Meteors _can_ travel at low velocities and in apparently horizontal paths.

3. _Size and brilliance._ Giant meteors of great luminosity have been recorded throughout history. Some fireballs have been visible to observers throughout an area of thousands of square miles. Typical descriptions are: dazzling, like an airplane falling in flames, bigger than the full moon, of blinding brilliance, so bright it turned night into day, like the headlight of a locomotive, as big as the setting sun but three times as brilliant.

The luminosity does not depend on the actual size of the meteoric body. A fragment no larger than a pinhead can create a brilliant flash as it vanishes. A spectacular fireball that lights up the country over hundreds of miles may have a small body that burns up completely miles above the earth. A larger body can survive longer, so that it continues to flare for several seconds or more. The larger, long-lasting fireballs may explode into smaller fragments and cascades of sparks. In exploding, they can produce a luminous cloud of particles that remains visible for fifteen or twenty minutes and then peppers the ground with meteorites that fall like hail or buckshot. A giant fireball can deposit chunks of metal weighing a ton or more like those found in Mexico, or can leave a truly enormous body that penetrates the ground and carves out a great crater like those in Arizona and Texas.

To summarize: Huge fireballs of great brilliance are not new.

4. _Sound._ Some meteors produce noise; others do not. Most meteors silently vaporize high above the earth. When one does reach the ground, it may strike with no noise but the faint thud of its impact. Shooting through the air, it sometimes makes weak noises that have been described as rumbling, crackling, rustling, whistling, or hissing.

Meteors sometimes explode with one or more crashing detonations that rattle or even break windows. The noise has been described as like a heavy clap of thunder, the explosion of a volcano, or a whir as if a million bumblebees had been disturbed. The noise from the explosion of the Siberian meteor in 1908 was heard over a distance of 600 miles, and the shock registered as an earthquake in England.

Many meteors, like the Pennsylvania fireball of January 29, 1952, (AMS 2328) are completely silent. This blue-green object, so large that it showed a definite disk, was reported to the American Meteor Society by more than 400 witnesses from Maine to Virginia and from New York to Ohio; none of the observers heard any noise [V-1, p. 264].

To summarize: Some meteors end with a bang, but most of them don’t even whimper.

5. _Fragments._ Most meteors burn up high in the atmosphere. A few, if they are large enough in size (at least ten to twenty pounds) and tough enough in structure, survive to reach the earth as stony or metallic fragments. Marked differences characterize the various meteor streams. The Taurids (maximum November 12) are relatively rigid structures, unusually tough, and show little tendency to break up in their flight. The many Taurid fireballs show that fairly large bodies have survived. The Geminids (maximum December 14) are of average strength but appear to be very dense, while the Draconids (October 10) are featherlike and fragile, with low density. Some of the most brilliant fireballs may be structures of ice and frozen gases which quickly vaporize on reaching the earth and hence leave no detectable fragments. The fiery object that struck Siberia in 1908 may have been such an “icy cometoid”; although it devastated an area of hundreds of square miles and uprooted or knocked down some eighty million trees, it apparently left no physical trace[V-15].