History of Astronomy From the Roman Empire to the Present, Part 6
This history of the evolution of astronomy would not be complete if we omitted to mention here the fact that, though the French school of astronomers had been foremost in adopting practical triangulation, it was not until the British took up the work in 1783 that the triangulation of the earth was seriously begun.
At about this time Immanuel Kant was laying the foundation of the Nebular Hypothesis— the theory that the earth and the planets were created by the sun.
Sir William Herschell became interested, and carried the thought further, but the Nebular Hypothesis may be said to have been still only in a nebulous state untill it was taken up and developed by the brilliant French mathematician and astronomer the Marquis de Laplace.
According to this hypothesis there was a time, ages ago, when there was neither earth, nor moon, nor planets, but only an immense mass of incandescent nebulous matter (where the sun is now), spinning and flaming like a gigantic Catherine wheel. . . alone amid the stars.
In other words there was only the sun, much larger than it is at the present time. This mass cooled and contracted, leaving a ring of tenuous blazing matter like a ring of smoke around it. In the course of time this ring formed itself into a solid ball, cooled, and became the planet Neptune.
The sun contracted again, leaving another ring, which formed itself into a ball and became the planet Uranus, and so it went on until Saturn, Jupiter, Mars, and then the Earth itself were created in a similar way; to be followed later by Venus and Mercury.
In this way Laplace explained how the earth and the planets came to be racing round the sun in the manner described by Copernicus; and, strange to say, this Nebular Hypothesis is now taught in the schools of the twentieth century with all the assurance that belongs to a scientific fact.
Yet the whole thing contradicts itself, for the laws of dynamics show that if the sun contracted it would rotate more rapidly, and if it rotated more rapidly that would increase the heat, and so cause the mass to expand.
It appears then, that as every attempt to cool increases the rotation, and heat, and so causes further expansion, the sun must always remain as it is. It cannot get cooler or hotter! and it cannot grow bigger or less! and so it is evident that it never could leave the smoke-like rings which Laplace imagined.
Therefore we know that the earth could never have been formed in that way; and never was part of the sun. This Nebular Hypothesis is pure imagination, and it is probable that it was only allowed to survive because it made an attempt to justify the impossible solar system of modern astronomy. It ends in smoke.
Just like a weed— which is always prolific— the Nebular Hypothesis soon produced another equally unscientific concept, known as the Atomic Theory. The idea that everything that exists consists of — or can be reduced to — atoms, was discussed by Anaxagoras and Democritus, away back in the days of Ancient Greece, but it was not until the beginning of the 19th century that it was made to account for the creation of the entire universe. Let us dissect it.
An atom is “the smallest conceivable particle of matter,” that is — smaller than the eye can see, even with the aid of a microscope; it is the smallest thing the mind of man can imagine. And the Atomic Theory suggests that once upon a time (a long way further back than Laplace thought of) there was nothing to be seen anywhere, in fact there seemed to be nothing at all but everlasting empty space; and yet that space was full of atoms smaller than the eye could see, and in some manner, which no one has been able to explain, these invisible atoms whirled themselves into the wonderful universe we now see around us. But if there had ever been a time when the whole of space was filled with atoms, and nothing else but atoms in a state of unity, they must have been without motion ; and being without motion, so they would have remained for ever ! . . . Of course the idea that all the elements could have existed in that uniform atomic state is preposterous, and shows the whole theory to be fundamentally unsound, but if — for the sake of argument — we allow the assumption to stand, the atomic condition goes crash against Newton’s “Laws of Motion,” which show that “ every thing persists in a state of rest until it is affected by some other thing outside itself.”
The tide of events now carries us along to the year 1824, when Encke made the first serious attempt to find the distance to the sun ; using as the means — the Transit of Venus.
He did not take the required observations himself, but made a careful examination of the records which had been made at the transits of 1761 and 1769, and estimated the sun’s distance from these; employing the method advocated by Dr. Hailey.
What is meant by the “Transit of Venus” is the fact of the planet passing between the observer and the sun (in daylight) when, by using coloured or smoked glasses to protect the eyes, it may be seen as a small spot moving across the face of the solar disk.
The method of finding the distance to the sun, at such a time, is as follows: Two observers are to be placed
as far apart as possible on the earth, as B and S in diagram lo. From these positions B will see Venus cross the face of the sun along the dotted line 2, while S will see the planet projected nearer to the top edge of the sun, moving along the lin e I . T h e distance which separates the two projections of Venus against the solar disk, indicated by the short vertical line I — 2 will bear a certain proportionate relation to the base-line— or diameter of the earth— which separates the observers B and S.
On referring to the Third Law of Kepler, laid down in the 17th century — it is calculated that the ratio of the line I — 2 as compared with the line B — S will be as 100 is to 37. Consequently, if we know the dimensions of the triangle from B and S to Venus it is a simple matter to find the dimensions of the triangle from Venus to the points i— 2 by the formvila— “ as 100 is to 37.”
Further, when we have found the number of miles that are represented by the space which separates the two dotted lines on the face of the sun, we can use the line i— 2 as though it were a yard-stick or a rule, and so measure the size of the sun from top to bottom.
Such is the method which Encke used in his study of the records of transits of Venus which had been made fifty years before, and it is stated on the most reliable authority that the results he obtained were accepted without question.
In round figures he made the sun to be about 97,000,000 miles from the earth and 880,000 miles from top to bottom. All this seems reasonable enough, and it certainly is ingenious ; and yet— The observers were not— as a matter of fact— placed at the poles, nor were they diametrically opposite to each other as in the diagram, but they observed the Transit of Venus from two other points not so favourably placed, and so “ allowances ” had to be made in order to find what the dimensions of the triangle B S Venus would have been if the observers had been there to see the transit. . . And in making these allowances our astronomers were all unconscious of the fact that if the observers really had been there (as in the diagram, and as illustrated in all books and lectures on the subject) they could not both have seen Venus at the same time, because A and B are upside down with respect to each other— their two horizons are opposite and parallel to each other— and the planet could not be above the two horizons at the same time. But the allowances were made, nevertheless, and the triangle, which, as we see, was more metaphysical than real, was referred to the Third Law of Kepler; which had been designed to fit a theory of the solar system which, so far, has not been supported by a single fact. The result of the entire proceeding was “nil.”