Myths and Marvels of Astronomy

by Richard A. Proctor

At the outset, let me point out that some observations which were for a long time regarded as mythical have proved to be exact. For instance, when as yet very few telescopes existed, and those very feeble, Galileo's discovery of moons travelling round Jupiter was rejected as an illusion for which Satan received the chief share of credit. There is an amusing and yet in one aspect almost pathetic reference to this in his account of his earlier observations of Saturn. He had seen the planet apparently attended on either side by two smaller planets, as if helping old Saturn along. But on December 4, 1612,[54] turning his telescope on the planet, he found to his infinite amazement not a trace of the companion planets could be seen; there in the field of view of his telescope was the golden-tinted disc of the planet as smoothly rounded as the disc of Mars or Jupiter. 'What,' he wrote, 'is to be said concerning so strange a metamorphosis? Are the two lesser stars consumed after the manner of the solar spots? Have they vanished or suddenly fled? Has Saturn, perhaps, devoured his children? Or were the appearances, indeed, illusion or fraud with which the glasses have so long deceived me as well as many others to whom I have shown them? Now, perhaps, is the time come to revive the well-nigh withered hopes of those who, guided by more profound contemplations, have discovered the fallacy of the new observations, and demonstrated the utter impossibility of the existence of those things which the telescope appears to show. I do not know what to say in a case so surprising, so unlooked for, and so novel. The shortness of the time, the unexpected nature of the event, the weakness of my understanding, and the fear of being mistaken, have greatly confounded me.' We now know that these observations, as well as those made soon after by Hevelius, though wrongly interpreted, were correct enough. Nay, we know that if either Galileo or Hevelius had been at the pains to reason out the meaning of the alternate visibility and disappearance of objects looking like attendant planets, they must have anticipated the discovery made in 1656 by Huyghens, that Saturn's globe is girdled about by a thin flat ring so vast that, if a score of globes like our earth were set side by side, the range of that row of worlds would be less than the span of the Saturnian ring system.

There is a reference in Galileo's letter to the solar spots; 'Are the two lesser stars,' he says, 'consumed after the manner of the solar spots?' When he thus wrote the spots were among the myths or fables of astronomy, and an explanation was offered, by those who did not reject them utterly, which has taken its place among forsaken doctrines, those broken toys of astronomers. It is said that when Scheiner, himself a Jesuit, communicated to the Provincial of the Jesuits his discovery of the spots on the sun, the latter, a staunch Aristotelian, cautioned him not to see these things. 'I have read Aristotle's writings from beginning to end many times,' he said, 'and I can assure you I have nowhere found in them anything similar to what you mention' [amazing circumstances!] 'Go, therefore, my son, tranquillise yourself; be assured that what you take for spots on the sun are the faults of your glasses or your eyes.' As the idea was obviously inadmissible that a celestial body could be marked by spots, the theory was started that the dark objects apparently seen on the sun's body were in reality small planets revolving round the sun, and a contest arose for the possession of these mythical planets. Tardé maintained that they should be called Astra Borbonia, in honour of the royal family of France; but C. Malapert insisted that they should be called Sidera Austriaca. Meantime the outside world laughed at the spots, and their names, and the astronomers who were thought to have invented both. 'Fabritius puts only three spots,' wrote Burton in his 'Anatomy of Melancholy,' 'and those in the sun; Apelles 15, and those without the sun, floating like the Cyanean Isles in the Euxine Sea. Tardé the Frenchman hath observed 33, and those neither spots nor clouds as Galileus supposed, but planets concentric with the sun, and not far from him, with regular motions. Christopher Schemer' in maculas et faculas, and will have them to be fixed in solis superficie and to absolve their periodical and regular motions in 27 or 28 dayes; holding withall the rotation of the sun upon his centre, and are all so confident that they have made schemes and tables of their motions. The Hollander censures all; and thus they disagree among themselves, old and new, irreconcilable in their opinions; thus Aristarchus, thus Hipparchus, thus Ptolomæus, thus Albategnius, etc., with their followers, vary and determine of these celestial orbs and bodies; and so whilst these men contend about the sun and moon, like the philosophers in Lucian, it is to be feared the sun and moon will hide themselves, and be as much offended as she was with those, and send another message to Jupiter, by some new-fangled Icaromenippus, to make an end of all these curious controversies, and scatter them abroad.'

It is well to notice how in this, as in many other instances, the very circumstance which makes scientific research trustworthy caused the unscientific to entertain doubt. If men of science were to arrange beforehand with each other what observations they should publish, how their accounts should be ended, what theories they would endeavour to establish, their results would seem far more trustworthy, their theories far more probable, than according to the method actually adopted. Science, which should be exact, seems altogether inexact, because one observer seems to obtain one result, another a different result. Scientific theories seem unworthy of reliance because scientific men entertain for a long time rival doctrines. But in another and a worthier sense than as the words are used in the 'Critic,' when men of science do agree their agreement is wonderful. It is wonderful, worthy of all admiration, because before it has been attained errors long entertained have had to be honestly admitted; because the taunt of inconsistency is not more pleasant to the student of science than to others, and the man who having a long time held one doctrine adopts and enforces another (one perhaps which he had long resisted), is sure to be accused by the many of inconsistency, the truly scientific nature of his procedure being only recognised by the few. The agreement of men of science ought to be regarded also as most significant in another sense. So long as there is room for refusing to admit an important theory advanced by a student of science, it is natural that other students of science should refuse to do so; for in admitting the new theory they are awarding the palm to a rival. In strict principle, of course, this consideration ought to have no influence whatever; as a matter of fact, however, men of science, being always men and not necessarily strengthened by scientific labours against the faults of humanity, the consideration has and must always have influence. Therefore, when the fellow-writers and rivals of Newton or of his followers gave in their adhesion to the Newtonian theory; when in our own time—but let us leave our own time alone, in this respect—when, speaking generally, a novel doctrine, or some new generalisation, or some great and startling discovery, is admitted by rival students of the branch of astronomy to which it belongs, the probability is great that the weight of evidence has been found altogether overwhelming.

Let us now, however, turn to cases in which, while many observations seem to point to some result, it has appeared that, after all, those observations must have been illusory.

A striking instance in point is found in the perplexing history of the supposed satellite of Venus.

On January 25, 1672, the celebrated astronomer, J.D. Cassini saw a crescent shaped and posited like Venus, but smaller, on the western side of the planet. More than fourteen years later, he saw a crescent east of the planet. The object continued visible in the latter case for half an hour, when the approach of daylight obliterated the planet and this phantom moon from view. The apparent distance of the moon from Venus was in both cases small, viz., only one diameter of the planet in the former case, and only three-fifths of that diameter in the latter.

Next, on October 23, 1740, old style, the optician Short, who had had considerable experience in observation, saw a small star perfectly defined but less luminous than Venus, at a distance from the planet equal to about one-third of the apparent diameter of our moon. This is a long distance, and would correspond to a distance from Venus certainly not less than the moon's distance from the earth. Short was aware of the risk of optical illusion in such matters, and therefore observed Venus with a second telescope; he also used four eye-pieces of different magnifying power. He says that Venus was very distinct, the air very pure, insomuch that he was able to use a power of 240. The seeming moon had a diameter less than a third of Venus's, and showed the same phase as the planet. Its disc was exceedingly well defined. He observed it several times during a period of about one hour.

Still more convincing, to all appearance, is the account of the observations made by M. Montaigne, as presented to the Academy of Sciences at Paris by M. Baudouin in 1761. The transit of Venus which was to take place on June 6 in that year led to some inquiry as to the satellite supposed to have been seen by Cassini and Short, for of course a transit would be a favourable occasion for observing the satellite. M. Montaigne, who had no faith in the existence of such an attendant, was persuaded to look for it early in 1761. On May 3 he saw a little crescent moon about twenty minutes of arc (nearly two-thirds the apparent diameter of our moon) from the planet. He repeated his observation several times that night, always seeing the small body, but not quite certain, despite its crescent shape, whether it might not be a small star. On the next evening, and again on May 7 and 10, he saw the small companion apparently somewhat farther from Venus and in a different position. He found that it could be seen when Venus was not in the field of view. The following remarks were made respecting these observations in a French work, 'Dictionnaire de Physique,' published in 1789:—'The year 1761 will be celebrated in astronomy in consequence of the discovery that was made on May 3 of a satellite circulating round Venus. We owe it to M. Montaigne, member of the Society of Limoges. M. Baudouin read before the Academy of Sciences at Paris a very interesting memoir, in which he gave a determination of the revolution and distance of the satellite. From the calculations of this expert astronomer we learn that the new star has a diameter about one-fourth that of Venus, is distant from Venus almost as far as the moon from our earth, has a period of nine days seven hours' [much too short, by the way, to be true, expert though M. Baudouin is said to have been], 'and its ascending node'—but we need not trouble ourselves about its ascending node.