Multitudes of meteors infest space.
The various kinds of meteors are probably but different manifestations of similar objects.
It can be shown that unless a quantity of meteors in collective mass equal to our moon were to plunge into the sun every year the supply of heat could not be sustained from this source.
The smallest and most numerous class are the telescopic meteors invisible to the naked eye.
It is computed that twenty millions of meteors enter the atmosphere every day and would be visible to unassisted vision in the absence of sunlight, moonlight and clouds, while if telescopic meteors are included the number will be increased twentyfold.
Ordinary meteors, in the region of the earth's orbit, appear to be separated by intervals of about 250 m.
The meteors, whatever their dimensions, must have motions around the sun in obedience to the law of gravitation in the same manner as planets and comets - that is, in conic sections of which the sun is always at one focus.
The great variety in the apparent motions of meteors proves that they are not directed from the plane of the ecliptic; hence their orbits are not like the orbits of planets and short-period comets, which are little inclined, but like the orbits of parabolic comets, which often have great inclinations.
The explanation of these recurring phenomena is that a great cloud or distended stream of meteors revolves around the sun in a period of 331years, and that one portion of the elliptical orbit intersects that of the earth.
As the meteors have been numerously visible in five or six successive years it follows they must be pretty densely distributed along a considerable arc of their orbit.
Per second in an opposite direction, so that the apparent velocity of the meteors is about 44 m.
The following is a list of the chief radiant points visible during the year: Many meteors exhibit the green line of magnesium as a principal constituent.
The night was clear and cool, the sky a beautiful pageant of dark blue silk and brilliant stars, of streaking meteors and two glowing orbs.
The book will contain four essays, all in French, with the general title of Project of a Universal science, capable of raising our nature to its highest perfection; also Dioptrics, Meteors and Geometry, wherein the most curious matters which the author could select as a proof of the universal science which he proposes are explained in such a way that even the unlearned may understand them.'
Besides the last two parts of the Principles of Philosophy, the physical writings of Descartes include the Dioptrics and Meteors, as well as passages in the letters.
Only one external source can be named: the falling of meteors into the sun must yield some heat just as a shooting star yields some heat to our atmosphere, but the question is whether the quantity of heat obtainable from the shooting stars is at all adequate for the purpose.
Now there is no reason to believe that meteors in anything like this quantity can be supplied to the sun, and, therefore, we must reject this source as also inadequate.
Among the Greeks and Romans various speculations as to the cause of the how were indulged in; Aristotle, in his Meteors, erroneously ascribes it to the reflection of the sun's rays by the rain; Seneca adopted the same view.
Descartes strengthened these views, both by experiments and geometrical investigations, in his Meteors (Leiden, 1637).
In ancient times meteors were supposed to be generated in the air by inflammable gases.
The attention devoted to the matter soon elucidated the phenomena of meteors, and proved them to be small planetary bodies, practically infinite in numbers and illimitable in the extent and variety of their orbits.
It may either be interspersed with many smaller meteors in a shower or may be isolated, The latter usually move more slowly and approach rather near to the earth.
More than a thousand observations in duplicate have been made of the paths of identical meteors seen from two stations many miles apart.
And some, usually slow-moving meteors, descend below 40 m.
The slower class of meteors overtaking the earth (like the Andromedids of November) have a velocity of about 8 or 10 m.
It also follows that, as some of the meteors are seen annually, they must be scattered around the whole orbit.
The meteors move very slowly, as they have to overtake the earth, and their apparent velocity is only about 9 m.
Biela's comet of 1826, which had a period of 6.7 years, presented a significant resemblance of orbit with that of the meteors, but the comet has not been seen since 1852 and has probably been resolved into the meteoric stream of Andromedids.
Rich annual displays of meteors have often been remarked on about the 10th of August, directed from Perseus, but they do not appear to have exhibited periodical maxima of great strength.
But the times of revolution are doubtful; the probable period of the comet is 121 years and that of the meteors 1051 years.
There was a brilliant exhibition of meteors on the 10th of April 1803, and in other years meteors have been very abundant on about the 19th to the 21st of April, shooting from a radiant a few degrees south-west of a Lyrae.
A comet which appeared in 1861 had a very suggestive agreement of orbit when compared with that of the meteors, and the period computed for it was 415 year's.
Bright meteors often emit the bluish-white light suggestive of burning magnesium.
Really large meteors can be satisfactorily photographed, but small ones leave no impression on the plates.
Meteors look larger than they are, from the glare and flaming effect due to their momentary combustion.
The finer meteors on entering the air only weigh a few hundred or, at most, a few thousand pounds, while the smallest shooting stars visible to the eye may probably be equal in size to coarse grains of sand, and still be large enough to evolve all the light presented by them.
He intended to follow it up with similar treatises on Mars, Jupiter, sun, moon, comets and meteors, stars, and nebulae, and had in fact commenced a monograph on Mars, when the failure of a New Zealand bank deprived him of an independence which would have enabled him to carry out his scheme without anxiety as to its commercial success or failure.
Formerly classified by the ancient Greeks with halos, rainbows, &c., under the general group of "meteors," they came to receive considerable attention at the hands of Descartes, Christiaan Huygens, and Sir Isaac Newton; but the correct explanation of coronae was reserved until the beginning of the 19th century, when Thomas Young applied the theories of the diffraction and interference of light to this phenomenon.
His great contribution to astronomy dates from 1866, when he showed that meteors or shooting stars traverse space in cometary orbits, and, in particular, that the orbits of the Perseids and Comet III., 1862, and of the Leonids and Comet I., 1866, were practically the same.
Using a powerful and elaborate analysis, Adams ascertained that this cluster of meteors, which belongs to the solar system, traverses an elongated ellipse in 334 years, and is subject to definite perturbations from the larger planets, Jupiter, Saturn and Uranus.
The most remarkable event, however, in the recent history of cometary astronomy was its assimilation to that of meteors,which took unquestion able cosmical rank as a consequence of the Leonid tempest of November 1833.
Schiaparelli's announcement that the orbit of the bright comet of 1862 agreed strictly with the elliptic ring formed by the circulating Perseid meteors; and three other cases of close coincidence were soon afterwards brought to light.
He attempted, not without success, to give a scientific account of eclipses, meteors, rainbows and the sun, which he described as a mass of blazing metal, larger than the Peloponnesus; the heavenly bodies were masses of stone torn from the earth and ignited by rapid rotation.
The only source of doubt as to the validity of the conclusion that this is really the zodiacal light arises from the possibility that, after the close of the ordinarily recognized twilight, there may be a faint illumination arising from the reflection of light by the very rare upper atmosphere, shown by the phenomena of meteors to extend some hundred miles or more above the earth's surface.
It was the brilliant exhibition in November 1833 that, in modern times particularly, attracted earnest students to investigate the subject of meteors generally, and to make systematic observations of their apparitions on ordinary nights of the year.