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Updated: June 28, 2025
It approaches the Sun, so as to be nearer to it than our Moon is to us, whilst it recedes to a distance 853 times greater than the distance of the Earth from the Sun. On the 17th of December, 1680, it was at its perihelion that is, at its greatest proximity to the Sun; it is now continuing its path beyond the Neptunian orbit. Its velocity varies according to its distance from the solar body.
"I know this, sir, that at 47 minutes 35.6 seconds after two o'clock on the morning of the 1st of January last, Gallia, in passing its ascending node, came in contact with the earth; that on the 10th of January it crossed the orbit of Venus; that it reached its perihelion on the 15th; that it re-crossed the orbit of Venus; that on the 1st of February it passed its descending node; on the 13th crossed the orbit of Mars; entered the zone of the telescopic planets on the 10th of March, and, attracting Nerina, carried it off as a satellite."
Professor Cleveland Abbe was fully persuaded that the long rays carefully observed by him from Pike's Peak were nothing else than streams of meteorites rushing towards or from perihelion; and it is quite certain that the solar neighbourhood must be crowded with such bodies.
A famous example of this kind of planetary horse-play is furnished by the story of Lexell's missing comet. This comet was first seen in 1770. Investigation showed that it was moving in an orbit which should bring it back to perihelion every five and a half years; yet it had never been seen before and, although often searched for, has never been seen since.
At perihelion it penetrates within the orbit of Mercury; it considerably transcends at aphelion the farthest excursion of Pallas. Its vicinity to the former planet in August, 1835, offered the first convenient opportunity of placing that body in the astronomical balance.
But it is always there, and whether soft in the gentler periods, or strong amidst the noise and clang of the perihelion, it dominates always and gives its tone to the whole life. The dominant tone of Sir John Meredith's existence had been the high clear note of battle. He had always found something or some one to fight from the very beginning, and now, in his old age, he was fighting still.
"The point where they approach nearest the sun when they pass the perihelion, I was going to say, the heat they endure must be terrific; when on the other hand, at their extreme distance from that body, the cold must be intense. The comet of 1680 did not approach within five thousand myriamètres of the sun."
When the earth is nearest the sun she is in her perihelion; and in her aphelion at the farthest point. Speaking of the moon, she is nearest to the earth in her perigee, and farthest from it in her apogee.
"The same difficulty with comets; there must have been some very urgent necessity for human beings in order to have peopled them. When they pass the perihelion " "The what?" inquired Willis.
The alteration of its position with respect to the stars amounts to about 11" in a year, but since the equinox is regressing in the opposite direction at the rate of 50" in a year, the whole annual variation of the longitude of the terrestrial perihelion amounts to 61". Laplace has considered two remarkable epochs in connection with this fact; viz: the epoch at which the major axis of the earth's orbit coincided with the line of the equinoxes, and the epoch at which it stood perpendicular to that line.
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