The Meadows of Eternity
Ix less than two hundred pages Dr. Macpherson has given us a concise history of proper astronomy—unfortunately not 'touching Greek speculation. Sugaring this with biographical sketches of the greater pioneers, he has led up to recent developments. The result is a book of great value, and thoUgh the later chapters dealing with the nature and the origin of the universe are likely to prove tough meat to the milk-teeth of the average reader, he should be encouraged to persevere. Without higher mathematics he could find no better way than this book offers to a general idea of the articulation of the heavens. His curiosity as to where modern astronomy is tending will also be satisfied—if one can be Satisfied by arriving at a junction where signposts to truth and adventure point in every direction.
The first, because the most intimate, idea we get from the book is of the quality and comparative significance of the great astronomers since the day of Copernicus, the father of them all. The conviction grows on us that, amid all these master minds, William Herschel stands out as the most powerful and original. As he claimed in his old age, he " looked further into space than ever human being did before him." In experiment and theory he led the way into every department of astronomical knowledge. He made possible our present conception of the meaning of time and space. He discovered the motion of the sun, and thereby lifted astronomy out of its local concern with the planetary system, and put that small pattern into perspective with the vast stellar design beyond it. In order to do this he revolutionized the telescope, making in his amateur way—for he was a music- :master at Bath—out of lenses and cardboard an instrument with which he discovered the planet Uranus. That was his beginning. His final and greatest achievement was the dis_ eovery of the existence of multitudes of faint filmy objects called nebulae, and his inductions therefrom of the shape, `dimensions, and organism of the Galactic Universe.
I had occasion to write here some time ago of modern inquiry into the nature of these nebulae. They are indeed the 'main object of inquiry to-day, and the conflict of opinions wages fast and furious. Herschel believed that these wisps of cosmic mist were really clusters of stars vast distances away ; .self-continent universes that had no concern with the Galactic ;Universe in which we and all the visible heaven of' stars are included. For nearly a century that belief has been com- bated by the theory that these nebulae are a sort of • moraine to the Milky Way, which with its eternal stream of moving Stars might be likened to a glacier. On this theory the nebulae consist of cosmic star-dust, a kind of atomic existence almost too devoid of gravity to be called matter. Sometimes they move dark and cold in space ; other masses accompany pertain giant stars, and shine with a light reflected from them. Another theory was that these shining nebulae generated their own radiance.
All these speculations, however, are being unified as know- ledge of cosmology becomes augmented by experiment. It seems that the whole of space is perhaps saturated by this incredibly rarefied cosmic " mist," and that periodically it thickens up into a coherent magnetic knot. That process con- tinued gives birth to " stars "—vague, vast suns that seem to consist more of forces than matter. Such was the sun at one time—a body whose diameter equalled the present orbit of the whole Solar System. Such to-day is, for instance, the first-magnitude star Betelgeuse, with a diameter of 273 million miles. Antares, that sinister monster who is believed by the astrologers to play such havoc in human destinies, certainly justifies his reputation for undue influence, since his diameter is 400 million miles.
So the mastery of space advances, and to-day we are beginning to see that this infinity of detached universes goes on still—but with a limit—a space limit, calculated by Einstein and others to be within a circumference of 1,000 million light- years.* It is possible that after travelling for this period of time the rays of sunshine and starlight return to their sources. In consequence, the original image of' a heavenly body is pre- sented to the same body which is now altered by its evolution through these aeons of time. The process might be compared to that of an idea which leaves our minds in childhood and in our old age is brought back vividly to us—but with what, a difference ! It is believed that as a result of this definition of infinity within a sphere or an ellipse many of the distant universes which we see to-day—the furthest one yet mea- sured is over a million light-years away—are returning images of our own Stellar System, physically visible phantoms of our past !
Let us look at our own system. All around us on this clear night is the multitude of the stars. Across the middle sky, cutting through the Zodiac, is the film of the Milky Way. That film is the vanishing perspective down the long column of the trooping suns. The stars covering the rest of the sky are our fellow-rankers with whom we march shoulder to shoulder. The whole heaven is but one rank deep, as it were. Yet the thickness of that one rank is some six hundred light-years, This great army consists of divisions, each one a star-cluster performing its own manoeuvres—but all acting in relation to the whole. Our Solar System belongs to the cluster that pivots round Sagittarius.
I could go on about the age of stars, and the new theories of the origin of star-systems, how they are the result of centri- petal and not centrifugal force. But I must remind readers that a proposal to erect a Stellarium in London has recently been put before the London County Council. Nearly every other capital in Europe has one. Let us hope that the people who are pressing for this may be successful. In the mean- while, here is Dr. Macpherson's book.
RICHARD CHURCH'.
* A light-year is the distance covered in one year by a ray of light travelling at the rate of 182,000 miles per second.
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