TRANSITS OF VENUS OVER THE SUN'S DISK, FROM THE YEAR 1769 TO THE YEAR 2004 INCLUSIVE. Geocentric longitude of the Sun and Venus, The earth is the next planet above 5 29 40 S D. M. S. 2 17 54 23 11 19 South. Venus, in the Solar Sytem; it is 95,000,000 of miles from the Sun, and performs a revolution around him, from any Solstice, or Equinox, to the same again, in 365 days, 5 C hours and 49 minutes: but from any fixed star to the same again, in 365 days, 6 hours and 9 minutes. The former being the length of the tropical year, and the latter the sidereal. It travels at the rate of 58,000 miles every hour, in performing its annual revolution. It revolves on its own axis from West to East, once in 24 hours. Its mean diameter as seen from the Sun, is 17 seconds and two tenths of a degree. Which, by calculation, will give about 7,970 miles for its diameter. The form of the earth is an oblate spheroid, whose equatorial axis exceeds its polar by 36 miles, and is surrounded by an atmosphere extending 45 miles above its surface. The Seas, and unknown parts of the earth, (by a measurement of the best Maps,) contain 160 millions, 522 thousand, and 26 square miles. The inhabited parts 38 millions, 990 thousand, 569. Europe four millions, 456 thousand, and 65. Asia 10 millions, 568 thousand, 823. Africa 9 millions, 654 thousand, 807. America 14 millions, 110 thousand, 874: the whole amounting to 199 millions, 512 thousand, 595; which is the number of square miles, on the whole surface of the Globe we inhabit. The Moon is not a planet, but only a satellite, or an attendant of the earth, performing a revolution round it in 29 days, 12 hours and 44 minutes; and with the earth, is carried round the Sun once in every year. The diameter of the Moon is 2,180 miles, and her mean distance from the earth's centre, is estimated at 240,000 miles. She goes around her orbit in 27 days, 7 hours and 43 minutes; moving about 2,290 miles every hour, and performs a revolution on her own axis exactly in the time that she goes round the earth; consequently the same side of her is continually presented towards the earth, and the length of her day and night taken together, is equal to a lunar month. Her mean apparent diameter, as seen from the earth, is 31 minutes and 8 seconds of a degree. The orbit of the Moon, crosses the ecliptic in two opposite points, called the Moon's nodes, consequently one half of her orbit is above the ecliptic, and the other below; the angle of its obliquity is 5 degrees, and 20 minutes. The Moon has scarcely any difference of seasons, because her axis is nearly perpendicular to the ecliptic, and consequently the Sun never removes sensibly from her equator. The earth which we inhabit, serves as a satellite to the Moon, waxing and waning regularly, but appearing thirteen times as large, and affording her, thirteen times as much light as the Moon does to us. When she is new to us, the earth appears full to her; and, when she is in her first quarter as seen from the earth, the earth is in its third quarter as seen from the Moon. The Moon is an opaque globe, like the earth, and shines only by reflecting the light of the Sun; therefore whilst that half of her which is towards the Sun, is enlightened, the other half must be dark and invisible. Hence she disappears when she comes between us and the Sun; because her dark side is then towards us. The planet Mars is next in order, being the first above the earth's orbit. His distance from the Sun is computed at 144,000,000 of miles, and by travelling at the rate of 54,000 miles every hour, he goes round the Sun in 686 of our days, 23 hours and 30 minutes, which is the length of his year, equal to 667 and 3-4th of his days; and every day and night together, being nearly 40 minutes longer than with us. His diameter is computed at 4,189 miles, and by his diurnal rotation, the inhabitants at his equator are carried 528 miles every hour. The Sun appears to the inhabitants of Mars, nearly two-thirds the size that it does to us. His mean apparent diameter, as seen from the earth is 27 seconds, and as seen from the Sun, ten seconds of a degree. His axis is inclined to his orbit 59 degrees and 22 minutes. To the inhabitants of the planet Mars, our Earth and Moon appear like two Moons; the one being 13 times as large as the other; changing places with each other, and appearing sometimes horned, sometimes half or three-quarters illuminated but never full, nor at most above one quarter of a degree from each other; although they are in fact 240,000 miles asunder. This Earth appears almost as large from Mars as Venus does to us. It is never seen above 48 degrees from the Sun, at that planet. Sometimes it appears to pass the disk of the Sun, and likewise Mercury and Venus. But Mercury can never be seen from Mars by such eyes as our's (unless assisted by proper instruments,) and Venus will be as seldom seen as we |
