A Trip to Venus: A Novel by John Munro (best books for 7th graders .TXT) 📖

"Very well, my little man, have you any idea how many stars you can see on a clear night?"

"Billions."

"No, Tommy. You are wrong, my dear boy. Go to the foot of your class. With the naked eye we can only distinguish three or four thousand, but with the telescope we are able to count at least fifty millions. They are thickest in the Milky Way, which, as you can see, runs all round the heavens, over your head, and under your feet, like an irregular tract of hazy light, a girdle of stars in short. Of course we cannot tell how many more there are beyond the range of vision, or what other galaxies may be scattered in the depths of space. The stars are suns, larger or smaller than our own, and of various colours—white, blue, yellow, green, and red. Some are single, but others are held together in pairs or groups by the force of gravitation. From their immense distance they appear fixed to us, but in reality they are flying in all directions at enormous velocities. Alpha, of the constellation Cygnus, for example, is coming towards us at a speed of 500 million leagues per annum, and some move a great deal faster. Most of them probably have planets circling round them in different stages of growth, but these are invisible to us. Here and there amongst them we find luminous patches or 'nebulæ,' which prove to be either clusters of stars or stupendous clouds of glowing gases. Our sun is a solitary blue star on the verge of the Milky Way, 20 billion miles from Alpha Centauri his next-door neighbour. He is travelling in a straight line towards the constellation Hercules at the rate of 20,000 miles an hour, much quicker than a rifle bullet; and, nevertheless, he will take more than a million years to cover the distance. Eight large or major planets, with their satellites, and a flock of minor planets or planetoids, are revolving round him as their common centre and luminary at various distances, but all in the same direction. The orbits, or paths, about the sun are ovals or ellipses, almost circular, of which the sun occupies one focus, and they are so nearly in one plane, or at one level, that if seen from the sun, they would appear to wander along a narrow belt of the heavens, called the zodiac, which extends a few degrees on each side of the Elliptic or apparent course of the sun against the stars. The planets are all globes, more or less flat at the poles, like an orange, and each is turning and swaying on its axis, thus exposing every part to the light and warmth of the sun. They are divided by the planetoids into an inner and an outer band. The inner four are Mercury, Venus, the Earth, and Mars; the outer four are Jupiter, Saturn, Uranus, and Neptune. Moreover, a number of comets and swarms of meteoric stones or meteorites are circulating round the sun in eccentric paths, which cross those of the planets. Such is the solar system—a lonely archipelago in the ethereal ocean—a little family of worlds."

"Not without its jars, I'm afraid."

"The sun is chief of the clan," continued Gazen, "and keeps it together by the mysterious tie of gravitation. While flying through space, he turns round his own axis like a rifle bullet in 25 or 26 days. His diameter is 860,000 miles, and although he is not much denser than sea-water, his mass is over 700 times greater than the combined mass of all his retinue. Gravity on his surface being 28 times stronger than on the earth, a piece of timber would be as heavy as gold there, and a stone let fall would drop 460 feet the first second instead of 16 feet as here. He is built of the same kind of matter as the earth and other planets, but is hotter than the hottest electric arc or reverberatory furnace. Apparently his glowing bulk is made up of several concentric shells like an onion. First there is a kernel or liquid nucleus, probably as dense as pitch. Above it is the photosphere, the part we usually see, a jacket of incandescent clouds, or vapours, which in the telescope is seen to resemble 'willow leaves,' or 'rice grains in a plate of soup,' and in the spectroscope to reveal the rays of iron, manganese, or other heavy elements. What we call 'faculæ' (or little torches), are brighter streaks, not unlike some kinds of coral. The 'Sunspots' are immense gaps or holes in the photosphere, some of them 150,000 miles in diameter, which afford us a peep at the glowing interior. There are different theories as to their nature, hence they provide rival astronomers with an excellent opportunity of spotting each other's reputations. For instance, I look upon them as eruptions, and Professor Sylvanus Pettifer Possil (my pet aversion) regards them as cyclonic storms; consequently we never lose an opportunity of erupting and storming at each other. Above the photosphere comes a stratum of cooler vapours and gases, namely, hydrogen and helium, a very light element recently found on the earth, along with argon, in the rare mineral cleveite. Tremendous jets of blazing hydrogen are seen to burst through the clouds of the photosphere, and play about in this higher region like the flames of a coal fire. These are the famous 'red flames' or 'prominences,' which are seen during a total eclipse as a ragged fringe of rosy fire about the black disc of the moon. Some of them rush through the chromosphere to a height of 80,000 miles in 15 minutes.

"Higher still is the 'corona,' an aureole of silvery beams visible in a total eclipse, and resembling the star of a decoration. The streamers have been traced for hundreds of thousands of miles beyond the solar disc. It appears to consist of meteoric stones, illuminated by the sunlight as well as of incandescent vapours of 'coronium,' a very light element unknown on the earth, and probably, too, of electrical discharges. The 'zodiacal light,' that silvery glow often seen in the west after sunset, or in the east before sunrise, may be a prolongation of it."

"I daresay these meteorites are swarming about the sun like midges about a lamp," said I.

"And just as eager to get burnt up," replied Gazen, with a smile. "Let us pass now to the planets. The little one next the sun is Mercury, who can be seen as a rosy-white star soon after sunset or before sunrise. He is about 36 million miles, more or less, from the sun; travels round his orbit in 88 days, the length of his year; and spins about his axis in 24 hours, making a day and night. His diameter is 3,000 miles, and his mass is nearly seven times that of an equal volume of water. The attraction of gravity on his surface is barely half that on the earth, and a man would feel very light there. Mercury seems to have a dense atmosphere, and probably high mountains, if not active volcanoes. The sunshine is from four to nine times stronger there than on the earth, and as summer and winter follow each other in six weeks, he is doubtless rather warm.

"Venus, the 'Shepherd's Star,' and the brightest object in the heavens after the moon, can sometimes be seen by day, and casts a distinct shadow at night. She is about 67 million miles from the sun, revolves round him in 225 days, and rotates on her axis in 23 to 24 hours, or as Schiaparelli believes, in 224 days. Her diameter is 7,600 miles, and her mass nearly five times that of an equal volume of water. Gravity is rather less there than it is here. Like Mercury, she appears to have a cloudy atmosphere, and very high mountains. On the whole she resembles the earth, but is, perhaps, a younger as well as a warmer planet.

"The green ball, next to Venus, is, I need hardly say, our own dear little world. Terra, or the earth, is 93 million miles from the sun, goes round him in 365 days, and turns on her axis in 24 hours less four minutes. Her diameter is 7,918 miles, and her density is 5.66 times that of water. She is attended by a single satellite,