Part 8

PHOTOGRAPHY

The second great engine of astronomical research, that has been added during the past century, is photography. By this means exact maps may be taken of the heavens at any hour of the night, and the precise position of thousands of stars determined with the utmost exactitude. A chart of the heavens, made in this manner, is not only more complete but more accurate than the combined observations of any number of men could possibly be. Moreover, the photographic plate will record the existence of stars which cannot be seen even with the aid of the most powerful telescopes. This is due to the fact that the plate gradually collects light, and its cumulative effect is noticeable, when its immediate effect cannot be perceived. This power of photographic plates is most valuable, and cannot be duplicated in any other manner. We are assured on good authority that “an ordinary good portrait camera with a lens three or four inches in diameter, if properly mounted so that an exposure of several hours can be made, will show stars so minute that they are invisible even in the great Lick telescope.” An international photographic chart of the heavens is now under way, which, when finished, will represent an accurate catalog of every visible sun, star, and planet, in the sky. After this, any unusual body should be quickly discovered.

But photography is employed not only for mapping out the heavens, but for reaching the farthest stars. The moon and the sun have both been photographed repeatedly, and with most instructive results. The first good pictures of the moon were made by Dr. John W. Draper of New York City, in March, 1840. His son, Dr. Henry Draper, succeeded him in this work, and his photographs were considered the best until Rutherfurd began his remarkable work in 1865. After this, much important work was done in the Lick observatory, and elsewhere. The first picture of the sun was taken in 1845, by Fizeau and Foucault, on a daguerreotype plate. Sun spots, total eclipses, etc., are now studied in great detail by this means.

THE TIDES

Every particle of matter attracts every other particle of matter throughout the entire Universe. The Sun and the Moon both exert a definite pull upon the earth; the moon particularly, being the earth’s satellite, is (so to say) held in place by the earth. The moon, exerting this definite pull, naturally influences the water of the earth most of all, because water is a fluid, mobile body. A heaping-up of the water then occurs--“high tide.” But the moon also attracts the earth to some extent; and the consequence of this is that the water on the opposite side of the globe is, as it were, left behind, which causes a heaping-up of the water there also. Hence, there are two high tides daily, with an interval of 12 hours between them, on opposite sides of the globe.

When the sun and moon pull together, we have the highest tides--“spring tides.” When they do not pull together (being in different parts of the heavens) we have only the surplus pull of the moon over the sun, and the tides are consequently not so high. These are the “neap tides.” All tides act as a sort of check or brake upon the rotation of the earth on its axis--tending to slow down its speed to some extent. “Tidal waves” are due to a combination of special causes.

GRAVITATION

The mysterious influence or “pull” which various celestial bodies exert upon one another is known as gravity or gravitation. We know that masses of matter attract one another according to their size; the larger the body, the greater the force exerted, etc. Further, the influence decreases according to a definite law--according to the square of the distance between the two bodies. The innermost nature of gravitation is still largely a mystery--though various ingenious theories have been advanced in order to explain it. (See my article in “The Monist,” for July, 1913, and pp. 44-46 of “New Discoveries in Science” in the present series.) Gravitation is supposed to act throughout the whole Universe, so that all celestial bodies mutually influence one another, to some extent. Its speed, mode or action, etc., as well as its essence or true nature are, however, unknown even yet; they are still unsolved mysteries!

THE ETHER

At all events, gravitation is thought to act through, or by means of, the Ether--the nature of which is still another mystery! Lodge, in his “Ether of Space,” has given some interesting figures as to the enormous strain which the ether must be supposed to transmit or carry. Lack of space, however, prevents a further discussion of this interesting question; a brief summary may be found on pp. 53-55 of my book on “Chemistry for Beginners,” in the series of Blue Books. For our present purposes, it need only be said that the ether is the only hypothetical connecting-link between celestial bodies--since there is no air or atmosphere in interstellar space. And it is across or by means of this ether that gravitation must be exerted.

ATOMIC ANALOGIES

Recent investigations of the innermost structure of the atom have shown us that it is probably constituted on very much the same plan as our solar system--a central “sun” or proton, round which revolve the negative planets or “electrons.” This question I have treated more fully in my “Chemistry for Beginners,” pp. 42-44, to which the reader is referred.

THUNDER AND LIGHTNING

The lightning flash is merely a huge electric spark, such as may be seen between the terminals of any electric machine. In cases of flashes, or forked lightning, this “spark” is seen directly. Sheet lightning is observed when the original flash is hidden behind clouds, and only its reflection or effects are seen. The rumbling of thunder is due to the reverberations and echoes of the original “peal.” The peal is thought to be due to the sudden rushing together of the molecules of the upper atmosphere, which have been rent asunder by the flash--a sort of vacuum created. Camille Flammarion has written an interesting book on “Thunder and Lightning,” which may be consulted for further details.

FIREBALLS

These are virtually the same as “shooting stars” (q.v.,) and no essential difference can be pointed to, as to their origin or nature. They are not mere “blobs” of lightning, but solid bodies which sometimes burst, with a great noise--though they are usually noiseless. Many of them appear to be pear-shaped, but they may be seen to change their size and shape during the period of visibility. Fireballs are often accompanied by a train of sparks.

ATMOSPHERIC ELECTRICITY

The surface of the earth is constantly charged with negative electricity of a static character. The upper atmosphere is usually charged positively, though, this may vary according to circumstances. The earth and upper air thus resemble two sheets of tin-foil, with the air an imperfect dialectric between them. This may be broken down, especially in wet or damp weather. The effects upon the mental and physical health are often very noticeable (see Dexter: “Weather Influences,” etc.)

THE EARTH’S MAGNETISM

It has long been known that the magnetic pole does not coincide with the North Pole (or South Pole). The compass points to the magnetic north pole, and not to the true north pole. Lines of magnetic force seem to envelop the earth, terminating at the north and south poles, respectively. Although this is purely a terrestrial phenomenon, it is necessary to mention it here, since it has enabled us to explain, very largely, the remarkable manifestation known as

THE AURORA BOREALIS

This is usually seen in northern climes, and the reason for this is now clear. We know that the corpuscles discharged from a Crookes tube are deflected by a magnet. These corpuscles are discharged in immense numbers by the sun, and rain upon our earth. Now, the earth is a magnet, and these corpuscles are caught by the lines of force girdling our earth, and carried towards the poles, where they find themselves in an atmosphere comparable with high vacua. They then begin to give out the shifting and darting lights characteristic of the cathode rays, causing a certain luminosity. These darting and shifting lights would, on this theory, account for the Aurora Borealis--which is also known to vary with the number of sun-spots.

TIME: MEASUREMENT OF:

Our divisions of time are purely arbitrary, and are all based upon the revolution of our earth upon its axis, which thus constitutes a gigantic clock. All other clocks, watches, etc., are adjusted accordingly. This is really our only way of measuring time; subjective feelings are very illusory, and have to be checked-up by other means. The solar day is the basis of all our calculations--a month, a year, etc., being only so many days in length. Our earth, therefore, is the clock by which we measure the time of the Universe!

SPACE: MEASUREMENT OF:

The measurement of space is always a difficult problem, even for near-by objects (see my “Psychology for Beginners”). When applied to celestial bodies, it becomes immensely complicated, and the only wonder is that such apparently accurate measurements have in fact been made! Such measurements cannot, of course, ever be made directly, but must depend upon trigonometry and abstruse mathematical calculations. Most of them are based upon the following principles: If we observe a distant object from two different points-of-view, at a known distance apart, the angle formed by imaginary lines running from the object to one position, and to the other, can readily be calculated. Knowing this angle, much can be ascertained as to the size, distance, etc., of the distant body. If a distant star be viewed from opposite sides of the earth, we have here a known base-line of slightly more than 8,000 miles. But this is altogether too small for astronomical distances! A much longer base-line must be sought. Accordingly, observations are made of a distant star when the earth is (so to say) “north” of the sun, and further observations of the same star when the earth is (so to say) “south” of it--six months later, when the earth has traveled half-way through its orbit round the sun. The diameter of the earth’s orbit being known (186,000,000 miles, almost) we have here a base-line of this size for use in our measurement of the angle and subsequent calculations. Immense as this base-line is, however, it is too small for our purposes, for so immense are astronomical distances, that no change whatever can be observed in the relative positions of certain fixed stars--even when studied from such different positions in space! In other words, the star is so far distant that, when viewed from two positions in space, distant from one another nearly one hundred and eighty-six million miles, it appears to occupy the same position! But a mere summary of this question, and its details would involve an entire volume in itself!

THE INTERNATIONAL DAY LINE

Inasmuch as our earth revolves on its axis, a new day is beginning at some different moment all round the world. This being the case, how are we to fix some definite and official “starting point” for our day--since the day officially begins at midnight, and not at sunrise? To determine this, an arbitrary International Day Line has been drawn, on the 180th meridian--just half way round the globe from Greenwich. Fortunately, this falls in the Pacific Ocean, where there is almost no land. When the sun crosses this line, a new day begins. I have explained this more fully in my book “New Discoveries in Science” in the present series (pp. 40-42).