Mercury completes his orbit in 88 days and this is, of course, the length of his year. During this journey he always turns the same face to the sun. The heat on this side must therefore be terrible and the surface unmercifully scorched and possibly cracked. Moreaux, a French astronomer, thinks that it may even be so hot that it has oceans of lead and molten tin. A few features are discernible, and although faint, these features are fixed. The general impression gained is that the tiny planet is barren, rough and mountainous, bleak, seared and desolate, with one side sweltering in terrific heat and the other numbed with dark and cold. Since there is no appreciable atmosphere on Mercury, there must be no wind—no warm currents of air to flow from the hot side to the cold side, nor from the cold side to the hot side,—thus making what is already drear seem motionless and dead.
Yet there is often some alleviating quality to make the drear seem less drear. For instance, a slight exception may be taken to the statement that the day side of Mercury is always day and the night side always night. As an effect of libration, an oscillatory movement of the planet on its axis, there is a strip of ground on either side, where the dark and light hemispheres meet, upon which the sun rises and shines for 44 days and then sets, leaving it in 44 days of darkness. This strip of ground is 23½ angular degrees in breadth and enjoys a true day, although its "day" is as long as its year, and is equal to 88 of our earth-days.
THE STRANGE PLANET OF URANUS, THE ANCIENT GOD OF THE HEAVENS
Diameter—32,000 miles
Mercury, Venus, Mars and Jupiter have been known since antiquity but Uranus was the first planet to be discovered with the aid of a telescope. This planet was discovered in 1781 by William Herschel while mapping stars, and the very fact of its existence astounded the world. Because Galileo had named the satellites of Jupiter the Medician Stars after his patron, Herschel wished to name his newly discovered planet Georgium Sidus, in honor of George the Third. But foreign astronomers would not agree to this and until a name was decided upon, called the planet Herschel. Later, the planet was called Uranus after the most ancient of all the deities, and its sign was the sign of the world hung on the initial of Herschel. H In appreciation of the fact that he had discovered a planet, Herschel was made private astronomer to his king and later knighted.
Uranus is the smallest of the major planets and ranks next to the earth in size, which is the largest of the minor planets, yet there is a great difference in the size of these two planets, for the diameter of the earth is only 7927 miles, while that of Uranus is 32,000 miles. There is also as great a difference in the nature of these two worlds.
Uranus travels through space in an orbit at an average distance of 1,771,000,000 miles from the sun, encompassing the orbits of Saturn, Jupiter, the Planetoids, Mars, Earth, Venus and Mercury; an orbit so large that it takes the planet 84 years to complete its journey around the sun. It has only been a year and a half, according to time figured on Uranus, since Herschel first introduced this planet to earth-dwellers.
Although the year of Uranus is 84 of our years long, which causes long and remarkable seasons, its day is very short, for the planet turns so rapidly on its axis that it sees both day and night in 10 hours and 50 minutes. Even the few hours of daylight it enjoys are not very bright ones, or warm ones either, for the planet is so far from the sun (which appears as an intense point of light), that it receives only ¹⁄₃₇₀th as much light and heat as we do on earth.
The axis of Uranus is tipped 98 degrees from the perpendicular which causes not only extreme but peculiar seasonal changes. Since the axis of the planet is always pointing in the same direction and at one place in its 84-year journey points almost directly at the sun, each pole in turn is bathed in 42 years of dim daylight and then, when on the other side of the orbit, sleeps through a night that is just as long. Bürgel remarks that "an inhabitant born at the beginning of winter and dying at the age of forty, would never see daylight, or the sun, but live in everlasting darkness like the pit-ponies in coal mines. The contrary would be the case with the summer-born, who would know of night and the stars only from hearsay." Quite different from what life might enjoy on Jupiter, for Jupiter's axis is inclined only 3 degrees from the perpendicular and its year would be almost a perpetual spring.
Careful observations seem to indicate that Uranus is a gaseous body, although cooler and more solid than Saturn and Jupiter. This planet is immersed in an exceedingly dense atmosphere quite different in constitution from the light, diaphanous covering of air which encloses the ball of the earth. This is indicated by the broad absorption band in its spectrum.