Astronomy for beginners

Astrology

Those who have not studied this subject will often ask the question: “What is the difference between Astronomy and Astrology?” It is merely this: Astronomy studies the heavenly bodies, and their movements, etc., by all available scientific means; while astrology, also utilizing this material, further asserts that the particular relative positions which the sun, moon, planets and other heavenly bodies occupy at the moment of birth influence the individual born at that moment, and continue to influence him all through life. In other words, astrology is undoubtedly an exact science in so far as its astronomical data are concerned; but its further inference, as applied to the living human being, is not; it depends upon historic beliefs and traditions which have been handed-down for centuries. So far as astronomers have been enabled to ascertain, there is not the slightest scientific basis for any belief in astrology; assuredly it is a curious and interesting occult study, but it must be understood to lie within that realm, rather than in that of exact astronomical science.

Imagine a large open common; on it place a globe 2 feet in diameter, by way of representing the Sun; Mercury will then be represented by a mustard seed at a distance of 82 feet; Venus by a pea at a distance of 142 feet; the Earth also by a pea, at a distance of 215 feet; Mars will be a small pepper corn, at a distance of 327 feet; the Minor Planets by grains of sand at distances varying from 500 to 600 feet; then a moderate sized orange ¼ of a mile distant from the central point will represent Jupiter; a small orange ⅖ths of a mile, Saturn; a full-sized cherry, ¾ths of a mile, Uranus; and lastly a plum, at 1¼ miles, Neptune,--the most distant planet yet known,--though some astronomers suspect there may exist another planet still further off, and hope one day to find it. (On the same scale, the nearest “fixed” star would be 7,500 miles distant).

The nature and constitution of the sun have, of course, been studied intensively for many years by astronomers. The apparent surface of the sun is called the “photosphere” (light surface). It is the part that gives forth most of the light and heat. Above the photosphere lies a sheet of gas, probably from 500 to 1,000 miles thick, called the “reversing layer,” which is cooler than the photosphere. Outside the photosphere is another layer of gas, from 5,000 to 10,000 miles deep, called the “chromosphere” (cooler sphere). The outermost portion of the Sun is the “corona” (crown). It is a halo of pearly light surrounding the sun, but it cannot be seen except during a total eclipse. It is of irregular form, and gradually fades out into the blackness of space at a distance of from 1,000,000 to 3,000,000 miles. This must not be confounded with the so-called “prominences,” which are vast eruptions of flame, spurting out from the sun’s surface, and extending into space for enormous distances--perhaps half a million miles! These also travel with enormous velocity--five or six hundred miles per second. The earth would appear an insignificant speck of dust, in this vast, roaring furnace of flame!

Of late years, the question of the so-called “sun spots” has aroused a great deal of interest, partly by reason of the fact that they apparently affect electrical and magnetic conditions upon the earth. These “spots” seem to reappear at stated intervals, and about every eleven years reach their maximum intensity, (The period of the revolution of the sun on its own axis has been estimated by their study.)

Although the sun-spots were studied before the eighteenth century, it is only within the past few years that the significance of these enormous spots has become known. For long it was thought that they were merely the great volcanoes of the sun; centers of great heat, generated by the glowing, fiery gases of the sun. In 1908, however, Prof. Hale demonstrated that the sun-spots acted as attraction centers, which drew towards them the hydrogen of the solar atmosphere. “Subsequently, it was found that these spots are the seats of great cyclones, in which cool hydrogen gas is set whirling and is sucked down in the great mælstrom of the Sun, rushing into the center of the spot at the rate of 60 miles a second. Consequently the spots are the center of great solar disturbances, which are of an electromagnetic nature.” From this it was concluded (1) that the spots are cooler than the surrounding area; (2) they are centers of violent cyclones; and (3) they are magnetic fields of great intensity. The connection of sun-spots with our weather, and the relation of one to the other, have also been studied within the past few years.

Mercury

This is the smallest of the planets in our solar system, being only about 3,000 miles in diameter. It revolves round the sun in almost exactly 88 days, at a distance of approximately 36,000,000 miles, varying between 28½ million to 43½ million miles. Owing to its smallness, it is often difficult to see this planet, and a powerful telescope must be employed to study it effectually. It is thought that Mercury possesses mountains, but it is practically devoid of atmosphere. Dark, irregular spots have been observed upon the planet, and its surface is thought, by some astronomers, to resemble that of Mars, to a great extent. The solar heat on Mercury is about seven times that on us, owing to its proximity to the Sun. Schiaparelli, and others, have contended that the period of rotation of Mercury is exactly equal to its period of revolution round the Sun. If that be true, one side of the planet is always turned to the Sun, and the other side away from it. One side of the planet would thus be intensely hot, while the other side would be icy cold. Comparatively little is known concerning this small planet, though much study has been devoted to it.

Venus

This is one of the brightest and most beautiful “stars” in the sky, and has for long been the theme of poets. It is practically the same size as our earth, its diameter being approximately 7,500 miles. It travels round the Sun in 224 days, at a mean distance of 67,000,000 miles. It revolves on its own axis in about 23½ hours, so that its days are nearly the same as ours. It is thought that Venus has a fairly dense atmosphere, and also water-vapor, which proves the existence of water upon its surface. Dense layers of cloud exist in the upper regions of its atmosphere, making direct observations of its surface very difficult. For this reason, comparatively little is known as to the conditions on the surface of Venus. Every eighth year Venus passes through a period of great brilliance, being then so bright as to cast a shadow, like the Moon. Venus must have a higher temperature than our earth; its sky is always overcast; thunder and lightning must be never-ending. Some controversy has existed as to the habitability of Venus; but the consensus of opinion is that life would be practically impossible upon its surface.

The Earth

The earth on which we dwell was thought by the ancients to be the center of the entire Universe--the Sun, stars and the vast host of Heaven were thought to revolve around it. This was the so-called “geocentric” theory. It was later on displaced by the so-called “heliocentric” theory, when it was found that the Sun, and not the Earth, was the center of our system. It only remains to be said that our Earth is the third of the planets which revolve round the Sun--Mercury and Venus being nearer the Sun than we are, and the others still further removed in space. We are thus but one of a number of similar bodies moving through space, all revolving round the central Sun.

Mars

This now-famous planet is somewhat smaller than our earth, being about 5,000 miles in diameter. It travels round the Sun in 686 days, at a mean distance of 140,000,000 miles. The eccentricity of its orbit is considerable. Mars appears to us reddish in color, owing to the vast stretches of arid soil (desert) which exist upon its surface. Water exists, but it is relatively scarce; it is gradually drying-up, as it does in the case of all bodies of the kind--the water on our own earth is very gradually becoming less and less, as the centuries pass.

Mars has been drawn particularly to the public’s attention, of late years, by reason of the dispute (still raging) as to its habitability, and the character of its so-called “canals”--the more or less regular markings, like long, dark lines which have been seen to exist upon its surface. Its surface has accordingly been studied minutely for many years, but it may be said that no unanimity of opinion exists as to its being an inhabited planet. Says Kæmpffert, in his “Astronomy,” (pp. 183-84):

“The mapping of Mars is no recent matter, for even in 1659 a rough sketch of the surface of the planet was made by Huygens, in which the V-shaped markings at the equator, pointing to the north, can be identified as the Syrtis Major. This was followed by rough sketches from time to time down to 1840, when Maedler first began a systematic charting of the planet. His map was followed in 1864 by Kaiser’s, by Flammarion’s in 1876, and Greene’s in 1877. Drawings of various parts of the planet were made during these intervals, but were not combined into good charts.”

“Observations made by Prof. Lowell and his staff at the Observatory, at Flagstaff, Arizona, have had a study of this planet especially in view.... The surface of Mars as seen in the telescope, is composed of two white polar caps, which wane with the approach of summer; orange areas, which are supposed by Lowell to be deserts, and blue-green areas, which change their hue to orange during the Martian autumn and winter, and resume their verdant tint in spring. The planet is covered with a network of fine lines, first discovered by Schiaparelli, in 1877; and called by him ‘canals’--a designation by which they are still known. These canals connect the polar caps with the temperate and equatorial zones. According to Prof. Lowell, they may be regarded as planetary irrigation ditches, which serve the purpose of leading the melting water of the poles to those desert regions which would still blossom, if properly watered. The canals disappear with the approach of winter, and creep down from the poles towards the equator in summer--a phenomenon which long puzzled astronomers, until Pickering ingeniously suggested that we see, not the canals themselves (for they are much too narrow) but the vegetation which fringes their banks--which withers as the cold of winter descends, and which flourishes with the melting of the snows.”