A CENTURY’S PROGRESS IN ASTRONOMY.
CHAPTER I.
HERSCHEL THE PIONEER.
In astronomy, as in other sciences, the past hundred years has been a period of unparalleled progress. New methods have been devised, fresh discoveries have been made, new theories have been propounded; the field of work has widened enormously. In fact, the science of the heavens has become not only boundless in its possibilities, but more awe-inspiring and marvellous.
To whom in the main is this great advance due? To the great pioneer of what may be called modern astronomy—William Herschel. Not only did Herschel reconstruct the science and widen its bounds, but his powerful genius directed the course of nineteenth century research. As an astronomical observer he has never been surpassed. In the breadth of his views he was equalled only by Newton; and indeed he excelled Newton in his unwearied observations and his sweeping conceptions of the Universe. To quote his own remark to the poet Campbell, he “looked farther into space than ever human being did before him.”
Herschel studied astronomy in all its aspects. In all the branches of modern astronomy he was a pioneer. He observed the Sun, Moon, and planets, devoting special attention to Mars and Saturn. He doubled the diameter of the Solar System by the discovery of Uranus. He discovered several satellites and studied comets. He was pre-eminently the founder of sidereal astronomy. He discovered binary stars, thus tracing the law of gravitation in the distant star-depths; while to him is due the credit of the discovery of the motion of the Solar System. He founded the study of star-clusters and nebulæ, propounded the nebular hypothesis, and devised two methods of star-gauging. Above all, he was the first to attempt the solution of one of the noblest problems ever attacked by man—the structure of the Universe. In fact, the latter problem was the end and aim of his observations. As Miss Clerke remarks, “The magnificence of the idea, which was rooted in his mind from the start, places him apart from and above all preceding observers.” Most of the departments of modern astronomy find a meeting-place in Herschel, as the branches run to the root of the tree. He discussed astronomy from every point of view. Before, however, proceeding to examine the work of this great man, it is well to note a few of his characteristics. These characteristics, once understood, give us the key to his researches. Before we can master Herschel the astronomer we must understand Herschel the man.
Notwithstanding the fact that Herschel spent most of his life in England, and that he is included in the ‘Dictionary of National Biography,’ he was pre-eminently a German. Like most Germans his style of writing was somewhat obscure, and this was emphasised when he wrote in English, owing to his imperfect command of the language. Had he written in German as well as in English, he would probably have been better understood in his native country, where erroneous views of his theories were long entertained. Even so distinguished an astronomer as Wilhelm Struve, when translating Herschel’s papers into German, made a mistake when translating a certain passage, which leaves the erroneous impression that Herschel believed the Universe to be infinite—a mistake which would not have arisen had he written in German.
The student of Herschel should also be careful in quoting the views of the great astronomer. Had Herschel at the close of his life written a volume containing his final views on the construction of the heavens, this would not have been necessary; but Herschel did not write such a volume. His researches were embodied in a series of papers communicated to the Royal Society from 1780 to 1818. As he observed the heavens his opinions progressed, so that a statement of his views at any given time was by no means a statement of his final opinions. The late R. A. Proctor, who was the first great exponent of Herschel in England, has well said: “It seems to have been supposed that his papers could be treated as we might treat such a work as Sir J. Herschel’s ‘Outlines of Astronomy’; that extracts might be made from any part of any paper without reference to the position which the paper chanced to occupy in the entire series.”
Herschel, like the true student of nature, held theories very lightly. They were to him but roads to the truth. Unlike many scientists, he did not interpret observations by hypothesis: he framed his theories to fit his observations. If he found that a certain theory did not agree with what he actually saw in the heavens, he abandoned it: he did not hesitate to change his views as his investigations proceeded. “No fear of ‘committing himself,’” says Miss Clerke in her admirable work on ‘The Herschels,’ “deterred him from imparting the thoughts that accompanied his multitudinous observations. He felt committed to nothing but truth.”
In the mind of Herschel imagination and observation were marvellously blended. He was a philosophical astronomer. Although his imagination was a very vivid one he did not allow his fancies to run away with him, as Kepler sometimes did: on the other hand, he did not, like Flamsteed, refrain from speculating altogether. “We ought,” he wrote in 1785, “to avoid two opposite extremes. If we indulge a fanciful imagination, and build worlds of our own, we must not wonder at our going wide from the path of truth and nature. On the other hand, if we add observation to observation, without attempting to draw not only certain conclusions but also conjectural views from them, we offend against the very end for which only observations ought to be made.”
These characteristics—the lightness with which he held his theories, his vivid imagination, and his philosophical reasoning—are the secrets of Herschel’s success as an astronomer. Nearly all his ideas and speculations have been confirmed. As Arago has said, “We cannot but feel a deep reverence for that powerful genius that has scarcely ever erred.” Herschel, like all other great students of Nature, was deeply religious. He could not observe the heavens without feeling awed at the marvels which his telescopes revealed. In his own words, “It is surely a very laudable thing to receive instruction from the Great Workmaster of Nature.”