Meteoroid

“ But his result would require for each meteoroid an enormous mass, one far too great to be accepted as possible. Again, the supposed power of such small bodies, bodies so scattered as these are even in the densest streams, to break up the comets or other heavenly bodies, and also their power by intercepting the sun's rays to affect our weather, must in the absence of direct proof to the contrary be regarded as insignificant. ”

“ If the meteoroids are arranged at random, there should be a uniform shading away of light as we go from the sun. If the meteoroids are in streams along cometary orbits, all lines bounding the light and shade in the coronal light should evidently be approximately projections of conic sections, of which the sun's center is the focus. ”

“ The majority of the meteors we observe represent the heat-induced “evaporation” of exceedingly small fragments of cosmic matter. The smallest meteor-forming bodies reach the surface of the earth only as the finest of dust particles or as microscopic droplets of solidified meteorite melt.
These residues descend slowly through the atmosphere and may be carried for great distances. Afterwards, they may be found scattered so widely and uniformly on the ground that their presence in any given locality cannot be accounted for by the fall of any specific meteorite. ”

“ Yes, siree, that must have been a big meteor stone."
"Then it struck the earth right close to our camp, mark me," vowed Jud.
"Ain't I glad it didn't pick out this spot to drop on," crowed Nuthin. "Whew! guess we'd have been squashed flatter than that pancake you hear about."
"What are meteors made up of—they drop from stars; don't they?" asked Bob Tice.
"Oh! there's just millions and billions of 'em flying around loose," said Phil Towns, who liked to read of astronomy at times. "Lots of 'em happen to get caught in the envelope of air that surrounds the earth. ”

“ Meteorites, the name for meteors which have actually gone all the way through our atmosphere, are never regular in form or spherical. As a rule the iron meteorites are covered with pittings or thumb marks, due probably to the resistance and impact of the little columns of air which impede its progress, together with the unequal condition and fusibility of their surface material. The work done by the atmosphere in suddenly checking the meteor's velocity appears in considerable part as heat, fusing the exterior to incandescence. ”

“ There can be no doubt that the plunge of a meteor into the sun's atmosphere with the terrific velocity which it will necessarily acquire in consequence of the attraction of the sun, is accompanied by the transformation of the energy of the meteor's movement into light and heat. The quantity of energy that a meteor thus carries with it is so vast that it is hardly credible until the figures which express it and the grounds on which they are based have received due attention. ”

“ The compressed air in which the solid particles of the surface of the meteorite glow then rushes on all sides, but especially over the surface of the meteor behind it, where it encloses a pear-shaped vacuum which has been left by the meteorite, and so appears to the observer as a ball of fire. If several bodies enter the earth's atmosphere in this way at the same time, the largest among them precedes the others, because the air offers the least resistance to its proportionately smallest surface ”

“ In thus rapidly penetrating the air heat is generated, the meteor becomes incandescent, and the phenomena of the streak or train is produced. Before the object can pierce the dense lower strata of air its material is usually exhausted, but on rare occasions it withstands the fiery ordeal, and fragments of the original mass fall upon the earth.
Multitudes of meteors infest space. On a clear moonless night one person may count eight or ten shooting stars in an hour. ”

“ This particle may be as small as a tiny dust grain or as large as one of the minor planets which are called asteroids. Fortunately for the inhabitants of the earth, most of the meteor-forming masses encountered by our globe are of the “small-fry” variety!
As the rapidly moving particle plunges earthward through denser and denser layers of atmosphere, the air molecules offer ever-increasing resistance to its passage. This resistance heats up the meteorite body until it glows. ”

“ So they reject the theory that such dust found in the Podkamennaya Tunguska area is specifically connected with the meteorite that fell there a half century ago.
If sizable chunks of meteoritic material enter the atmosphere, they may produce exceptionally large and brilliant meteors. A spectacular meteor is generally known as a “fireball” if it is as bright as Venus or Jupiter. It receives the French term bolide if, in addition to showing great brilliance, its flight is accompanied by detonations like the alarming sounds heard at the time of the Ussuri and Norton meteorite falls. ”

“ The luminous meteor-tracks are in the upper part of the earth's atmosphere. Few, if any, appear at a height greater than one hundred miles, and few are seen below a height of thirty miles from the earth's surface, except in rare cases, when stones and irons fall to the ground. All these meteor-tracks are caused by bodies which come into the air from without.
2. The velocities of the meteors in the air are comparable with that of the earth in its orbit about the sun. ”

“ If it come to an aerolite or mass of metallic rock, or even a cloudlet of gas, standing still in space, its contact with our air evolves 600,000° of heat. And when the meteor comes toward the world twenty-six miles a second, the heat would become proportionally greater if the meteor could abide it, and not be consumed in fervent heat. It vanishes almost as soon as seen. If there were meteoric masses enough lying in our path, our sky would blaze with myriads of flashes of light. Enough have been seen to enable a person to read by them at night. ”

“ 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. ”

“ They are hundreds in number—meteors are millions. They have their region of travel, and the sun holds them and the giant Jupiter by the same power. The Power that cares for a world cares for a sparrow. If their orbit so lies that a planet passes through it, and the planet and the meteors are at the point of intersection at the same time, there must be collisions, and the lightning signs of extinction proportioned to the number of little bodies in a given space.
It is demonstrated that the earth encounters more than one hundred such systems of meteoric bodies in a single year. ”

“ Aloft, in the emptiness of space, there is no air to impede its flight. It may have been moving round and round the sun for thousands, perhaps for millions of years, without suffering any interference; but the supreme moment arrives, and the meteor perishes in a streak of splendour.
In the course of its wanderings the body comes near the earth, and within a few hundred miles of its surface begins to encounter the upper surface of the atmosphere with which the earth is enclosed. To a body moving with the appalling velocity of a meteor, a plunge into the atmosphere is usually fatal. ”

“ The special meteor family whose track the earth crosses on November 13-14 forms a mighty ellipse round the sun, extending more than 19 times farther from him than the track of our earth, which yet, as we know, lies more than 92,000,000 miles from the sun. Along this tremendous orbit the meteors speed with planetary but varying velocity, crossing the track of our earth with a velocity exceeding by more than a third her own swift motion of about 19 miles in every second of time. ”

“ A really large meteor is a grand sight. If it is seen at night it appears as a red star, growing rapidly bigger and leaving a trail of luminous vapour behind as it passes across the sky. In the daytime this vapour looks like a cloud. As the meteor hurls itself along there may be a deep continuous roar, ending in one supreme explosion, or perhaps in several explosions, and finally the meteor may come to the earth in one mass, with a force so great that it buries itself some feet deep in the soil, or it may burst into numbers of tiny fragments, which are scattered over a large area. ”

“ If the process went on for long the meteor would be all dissipated in vapour, and in any case it must reach the earth considerably reduced in size.
Numbers and numbers of comparatively small ones disappear, and for every one that manages to come to earth there must be hundreds seen only as shooting stars, which vanish and 'leave not a wrack behind.' When a meteor is seen to fall it is traced, and, whenever possible, it is found and placed in a museum. Men have sometimes come across large masses of stone and iron with their surfaces fused with heat. ”

“ The speed of the meteor is checked by the resistance which the atmosphere offers to its motion, and the energy represented by that speed is transformed into heat, which in less than a second raises the meteor and the surrounding air to incandescence, melts the meteor either wholly or in part, and usually destroys its identity, leaving only an impalpable dust, which cools off as it settles slowly through the lower atmosphere to the ground. ”

“ The theatre of one of the great meteoric exhibitions in question may be the aerial envelope, not only of a large planet or a vast dark central body presiding over unseen planetary members, but even the corona and the photosphere of a sun. Whenever any of the large members of a solar or of a secondary system become unstable in too small an orbit, a vast portion of its dilapidated mass would be quickly sweeping as innumerable meteors through the atmosphere of the immense primary sphere. ”

“ First of all, meteorites neither all look alike nor have the same composition. The general term “meteorite” applies to any mass that reaches the earth from space. Such masses are made up of metals and minerals in varying proportions. The term “meteorite” is nearly as general in meaning as the word “rock,” which geologists apply to bodies, large and small, that are formed by earth processes and are composed of various kinds of minerals. Actually, there are almost as many different kinds of meteorites as there are kinds of rocks ”

“ It is now generally received, and placed almost beyond doubt by the recent observations of Schiaparelli, Le Verrier, Weiss, and others, that these meteors, for the most part small, but weighing occasionally many tons, are fragmentary masses, revolving, like the planets, round the sun, which in their course approach the earth, and, drawn by its attraction into our atmosphere, are set on fire by the heat generated through the resistance offered by the compressed air. ”

“ It is true that difficulties have been urged against the view that meteorites have been derived from the globe on which we live. I have endeavoured to remove these difficulties, and I believe I have shown that they are, at all events, far less considerable than those which are experienced when we endeavour to attribute the meteorites to any other source that has been alleged. The objections that are felt to the view of the terrestrial origin of the objects are threefold. They are, firstly, the excessive initial velocity which would be required ”

“ Then, too, the movements of meteorites have a certain significance both for the astronomer and the mathematician. It is true that only the last stage of its wild career can be observed, for the flight of the meteorite for millions of preceding years is quite unknown, so far as any direct observations are concerned. The observer never beholds one of these bodies until that supreme moment when at the conclusion of its incalculable journey it flashes from the sky and strikes the earth beneath. ”

“ Also, as the point in space towards which the earth is moving in its orbit varies in height above the horizon during the year, being highest in autumn and lowest in spring, the number of shooting stars hourly visible at one place will gradually vary from night to night, reaching a maximum in the former season and a minimum in the latter, if the directions of flight of the meteorites be themselves uniformly distributed in space. ”

“ We have met with outbursts upon stars sometimes of sufficient violence to shoot off part of their substance. We have found the gaseous portion sweeping through space like a net, and the vapors that accompanied it condensed into spatters that have consolidated into meteorites. We have seen this system traveling through boundless space, with nothing near it except an occasional solitary meteor, and we have seen it in the long lapse of ages slowly augmenting its cluster of these little strangers. ”

“ From the above it will be evident that the old hypotheses that meteorites are terrestrial stones which have been struck by lightning, or carried to the sky by a whirlwind, or are concretions in the atmosphere, or are due to the condensation of a dust-cloud coming from some volcano, or have been shot recently from terrestrial volcanoes, are inconsistent with [pg 49] later observation; it may be granted that the bodies reach our atmosphere from outer space. ”

“ The meteor or asteroid belt, between the orbits of Mars and Jupiter, is "mined" by such adventurers as Thad Allen for the platinum, iridium and osmium that all meteoric irons contain in small quantities. The meteor swarms are supposed by some astronomers to be fragments of a disrupted planet, which, according to Bode's Law, should occupy this space. ”