The Beauties of Nature, and the Wonders of the World We Live In

by Sir John Lubbock

The proverbial spots on the Sun in many respects resemble the appearances which would be presented if a comparatively dark central mass was here and there exposed by apertures through the more brilliant outer gases, but their true nature is still a matter of discussion.

During total eclipses it is seen that the Sun is surrounded by a "corona," or aureola of light, consisting of radiant filaments, beams, and sheets of light, which radiate in all directions, and the true nature of which is still doubtful.

Another stupendous problem connected with the Sun is the fact that, as geology teaches us, it has given off nearly the same quantity of light and heat for millions of years. How has this come to pass? Certainly not by any process of burning such as we are familiar with. Indeed, if the heat of the Sun were due to combustion it would be burnt up in 6000 years. It has been suggested that the meteors, which fall in showers on to the Sun, replace the heat which is emitted. To some slight extent perhaps they do so, but the main cause seems to be the slow condensation of the Sun itself. Mathematicians tell us that a contraction of about 220 feet a year would account for the whole heat emitted, and as the present diameter of the Sun is about 860,000 miles, the potential store of heat is still enormous.

To the Sun we owe our light and heat; it is not only the centre of our planetary system, it is the source and ruler of our lives. It draws up water from the ocean, and pours it down in rain to fill the rivers and refresh the plants; it raises the winds, which purify the air and waft our ships over the seas; it draws our carriages and drives our steam-engines, for coal is but the heat of former ages stored up for our use; animals live and move by the Sun's warmth; it inspires the song of birds, paints the flowers, and ripens the fruit. Through it the trees grow. For the beauties of nature, for our food and drink, for our clothing, for our light and life, for the very possibility of our existence, we are indebted to the Sun.

What is the Sun made of? Comte mentioned as a problem, which it was impossible that man could ever solve, any attempt to determine the chemical composition of the heavenly bodies. "Nous concevons," he said, "la possibilité de déterminer leurs formes, leurs distances, leurs grandeurs, et leurs mouvements, tandis que nous ne saurions jamais étudier par aucun moyen leur composition chimique ou leur structure minéralogique." To do so might well have seemed hopeless, and yet the possibility has been proved, and a beginning has been made. In the early part of this century Wollaston observed that the bright band of colours thrown by a prism, and known as the spectrum, was traversed by dark lines, which were also discovered, and described more in detail, by Fraunhofer, after whom they are generally called "Fraunhofer's lines." The next step was made by Wheatstone, who showed that the spectrum formed by incandescent vapours was formed of bright lines, which differed for each substance, and might, therefore, be used as a convenient mode of analysis. In fact, by this process several new substances have actually been discovered. These bright lines were found on comparison to coincide with the dark lines in the spectrum, and to Kirchhoff and Bunsen is due the credit of applying this method of research to astronomical science. They arranged their apparatus so that one-half was lighted by the Sun, the other by the incandescent gas they were examining. When the vapour of sodium was treated in this way they found that the bright line in the flame of soda exactly coincided with a line in the Sun's spectrum. The conclusion was obvious; there is sodium in the Sun. It must, indeed, have been a glorious moment when the thought flashed upon them; and the discovery, with its results, is one of the greatest triumphs of human genius.

The Sun has thus been proved to contain hydrogen, sodium, barium, magnesium, calcium, aluminium, chromium, iron, nickle, manganese, titanium, cobalt, lead, zinc, copper, cadmium, strontium, cerium, uranium, potassium, etc., in all 36 of our terrestrial elements, while as regards some others the evidence is not conclusive. We cannot as yet say that any of our elements are absent, nor though there are various lines which cannot as yet be certainly referred to any known substance, have we clear proof that the Sun contains any element which does not exist on our earth. On the whole, then, the chemical composition of the Sun appears closely to resemble that of our earth.

THE PLANETS

The Syrian shepherds watching their flocks by night long ago noticed—and they were probably not the first—that there were five stars which did not follow the regular course of the rest, but, apparently at least, moved about irregularly. These they appropriately named Planets, or wanderers.

Further observations have shown that this irregularity of their path is only apparent, and that, like our own Earth, they really revolve round the Sun. To the five first observed—Mercury, Venus, Mars, Jupiter, and Saturn—two large ones, Uranus and Neptune, and a group of minor bodies, have since been added.

The following two diagrams give the relative orbits of the Planets.