Myths and Marvels of Astronomy

30

The reader who cares enough about such subjects to take the necessary trouble, can easily make a little model of Saturn and his ring system, which will very prettily illustrate the effect of the rings both in reflecting light to the planet's darkened hemisphere and in cutting off light from the planet's illuminated hemisphere. Take a ball, say an ordinary hand-ball, and pierce it through the centre with a fine knitting-needle. Cut out a flat ring of card, proportioned to the ball as the ring system of Saturn to his ball. (If the ball is two inches in diameter, strike out on a sheet of cardboard two concentric circles, one of them with a radius of a little more than an inch and a half, the other with a radius of about two inches and three-eights, and cut out the ring between these two circles.) Thrust the knitting-needle through this ring in such a way that the ball shall lie in the middle of the ring, as the globe of Saturn hangs (without knitting-needle connections) in the middle of his ring system. Thrust another knitting-needle centrally through the ball square to the plane of the ring, and use this second needle, which we may call the polar one, as a handle. Now take the ball and ring into sunlight, or the light of a lamp or candle, holding them so that the shadow of the ring is as thin as possible. This represents the position of the shadow at the time of Saturnian spring or autumn. Cause the shadow slowly to shift until it surrounds the part of the ball through which the polar needle passes on one side. This will represent the position of the shadow at the time of midwinter for the hemisphere corresponding to that side of the ball. Notice that while the shadow is traversing this half of the ball, the side of the ring which lies towards that half is in shadow, so that a fly or other small insect on that half of the ball would see the darkened side of the ring. A Saturnian correspondingly placed would get no reflected sunlight from the ring system. Move the ball and ring so that the shadow slowly returns to its first position. You will then have illustrated the changes taking place during one half of a Saturnian year. Continue the motion so that the shadow passes to the other half of the ball, and finally surrounds the other point through which the polar needle passes. The polar point which the shadow before surrounded will now be seen to be in the light, and this half of the ball will illustrate the hemisphere of Saturn where it is midsummer. It will also be seen that the side of the ring towards this half of the ball is now in the light, so that a small insect on this half of the ball would see the bright side of the ring. A Saturnian correspondingly placed would get reflected sunlight from the ring system both by day and by night. Moving the ball and ring so that the shadow returns to its first position, an entire Saturnian year will have been illustrated. These changes can be still better shown with a Saturnian orrery (see plate viii. of my Saturn), which can be very easily constructed.

31

Not 'of course' because Tycho used it, for, like other able students of science, he made mistakes from time to time. Thus he argued that the earth cannot rotate on her axis, because if she did bodies raised above her surface would be left behind—an argument which even the mechanical knowledge of his own time should have sufficed to invalidate, though it is still used from time to time by paradoxers of our own day.

32

Chinese chronicles contain other references to new stars. The annals of Ma-touan-lin, which contain the official records of remarkable appearances in the heavens, include some phenomena which manifestly belong to this class. Thus they record that in the year 173 a star appeared between the stars which mark the hind feet of the Centaur. This star remained visible from December in that year until July in the next (about the same time as Tycho Brahe's and Kepler's new stars, presently to be described). Another star, assigned by these annals to the year 1011, seems to be the same as a star referred to by Hepidannus as appearing a.d. 1012. It was of extraordinary brilliancy, and remained visible in the southern part of the heavens during three months. The annals of Ma-touan-lin assign to it a position low down in Sagittarius.

33

Still a circumstance must be mentioned which tends to show that the star may have been visible a few hours earlier than Dr. Schmidt supposed. Mr. M. Walter, surgeon of the 4th regiment, then stationed in North India, wrote (oddly enough, on May 12, 1867, the first anniversary of Mr. Birmingham's discovery) as follows to Mr. Stone:—'I am certain that this same conflagration was distinctly perceptible here at least six hours earlier. My knowledge of the fact came about in this wise. The night of the 12th of May last year was exceedingly sultry, and about eight o'clock on that evening I got up from the tea-table and rushed into my garden to seek a cooler atmosphere. As my door opens towards the east, the first object that met my view was the Northern Crown. My attention was at once arrested by the sight of a strange star outside the crown' (that is, outside the circlet of stars forming the diadem, not outside the constellation itself). The new star 'was then certainly quite as bright—I rather thought more so—as its neighbour Alphecca,' the chief gem of the crown. 'I was so much struck with its appearance, that I exclaimed to those indoors, "Why, here is a new comet!'" He made a diagram of the constellation, showing the place of the new star correctly. Unfortunately, Mr. Walter does not state why he is so confident, a year after the event, that it was on the 12th of May, and not on the 13th, that he noticed the new star. If he fixed the date only by the star's appearance as a second-magnitude star, his letter proves nothing; for we know that on the 13th it was still shining as brightly as Alphecca, though on the 14th it was perceptibly fainter.

34

The velocity of three or four miles per second inferred by the elder Struve must now be regarded (as I long since pointed out would prove to be the case) as very far short of the real velocity of our system's motion through stellar space.

35

M. Cornu's observations are full of interest, and he deserves considerable credit for his energy in availing himself of the few favourable opportunities he had for making them. But he goes beyond his province in adding to his account of them some remarks, intended apparently as a reflection on Mr. Huggins's speculations respecting the star in the Northern Crown. 'I,' says M. Cornu, 'will not try to form any hypothesis about the cause of the outburst. To do so would be unscientific, and such speculations, though interesting, cumber science wofully.' This is sheer nonsense, and comes very ill from an observer whose successes in science have been due entirely to the employment of methods of observation which would have had no existence had others been as unready to think out the meaning of observed facts as he appears to be himself.

36

The same peculiarity has been noticed since the discovery of the dark ring, the space within that ring being observed by Coolidge and G. Bond at Harvard in 1856 to be apparently darker than the surrounding sky.

37

I cannot understand why Mr. Webb, in his interesting little work, Celestial Objects for Common Telescopes, says that the satellite theory of the rings certainly seems insufficient to account for the phenomena of the dark ring. It seems, on the contrary, manifest that the dark ring can scarcely be explained in any other way. The observations recently made are altogether inexplicable on any other theory.

38

A gentleman, whose acquaintance I made in returning from America last spring, assured me that he had found demonstrative evidence showing that a total eclipse of the moon then occurred; for he could prove that Abraham's vision occurred at the time of full moon, so that it could not otherwise have been dark when the sun went down (v. 17). But the horror of great darkness occurred when the sun was going down, and total eclipses of the moon do not behave that way—at least, in our time.

39

It is not easy to understand what else it could have been. The notion that a conjunction of three planets, which took place shortly before the time of Christ's birth, gave rise to the tradition of the star in the east, though propounded by a former president of the Astronomical Society, could hardly be entertained by an astronomer, unless he entirely rejected Matthew's account, which the author of this theory, being a clergyman, can scarcely have done.

40

As, for instance, when he makes Homer say of the moon that

Around her throne the vivid planets roll,And stars unnumbered gild the glowing pole.

It is difficult, indeed, to understand how so thorough an astronomer as the late Admiral Smyth could have called the passage in which these lines occur one of the finest bursts of poetry in our language, except on the principle cleverly cited by Waller when Charles II. upbraided him for the warmth of his panegyric on Cromwell, that 'poets succeed better with fiction than with truth.' Macaulay, though not an astronomer, speaks more justly of the passage in saying that this single passage contains more inaccuracies than can be found in all Wordsworth's 'Excursion.'

41

It may be necessary to throw in here a few words of explanation, lest the non-astronomical reader should run away with the idea that the so-called exact science is a very inexact science indeed, so far as comets are concerned. The comet of 1680 was one of those which travel on a very eccentric orbit. Coming, indeed, from out depths many times more remote than the path even of the remotest planet, Neptune, this comet approached nearer to the sun than any which astronomers have ever seen, except only the comet of 1843. When at its nearest its nucleus was only a sixth part of the sun's diameter from his surface. Thus the part of the comet's orbit along which astronomers traced its motion was only a small part at one end of an enormously long oval, and very slight errors of observation were sufficient to produce very large errors in the determination of the nature of the comet's orbit. Encke admitted that the period might, so far as the comparatively imperfect observations made in 1680 were concerned, be any whatever, from 805 years to many millions of years, or even to infinity—that is, the comet might have a path not re-entering into itself, but carrying the comet for ever away from the sun after its one visit to our system.

42

For a portion of the passages which I have quoted in this essay I am indebted to Guillemin's 'Treatise on Comets,' a useful contribution to the literature of the subject, though somewhat inadequate so far as exposition is concerned.

43

Something very similar happened only a few years ago, so that we cannot afford to laugh too freely at the terrors of France in 1773. It was reported during the winter of 1871–1872, that Plantamour, the Swiss astronomer, had predicted the earth's destruction by a comet on August 12, 1872. Yet there was no other foundation for this rumour than the fact that Plantamour, in a lecture upon comets and meteors, had stated that the meteors seen on August 10, 11, and 12 are bodies following in the track of a comet whose orbit passes very near to the earth's. It was very certainly known to astronomers that there could be no present danger of a collision with this comet, for the comet has a period of at least 150 years, and had last passed close to the earth's orbit (not to the earth herself, be it understood) in 1862. But it was useless to point this out. Many people insisted on believing that on August 12, 1872, the earth would come into collision, possibly disastrous, with a mighty comet, which Plantamour was said to have detected and to have shown by a profound calculation to be rushing directly upon our unfortunate earth.

44

A rather amusing mistake was made by the stenographers of a New York paper in reporting the above sentence, which I happened to quote in a lecture upon Comets and Meteors. Instead of Paradise they wrote Paris. Those acquainted with Pitman's system of short-hand, the one most commonly employed by reporters, will easily understand how the mistake was made, the marks made to represent the consonants p, r, d, and s differing little from those made to represent the consonants p, r, and s (the 'd' or 't' sound is represented, or may be represented, by simply shortening the length of the sign for the preceding consonant). The mistake led naturally to my remarking in my next lecture that I had not before known how thoroughly synonymous the words are in America, though I had heard it said that 'Good Americans, when they die, go to Paris.'

45

On the occasion of my first visit to America, in 1873, I for the first time succeeded in obtaining a copy of this curious pamphlet. It had been mentioned to me (by Emerson, I think) as an amusing piece of trickery played off by a scientific man on his brethren; and Dr. Wendell Holmes, who was present, remarked that he had a copy in his possession. This he was good enough to lend me. Soon after, a valued friend in New York presented me with a copy.

46

This Locke must not be confounded with Richard Lock, the circle-squarer and general paradoxist, who flourished a century earlier.

47

The nurses' tale is, that the man was sent to the moon by Moses for gathering sticks on the Sabbath, and they refer to the cheerful story in Numbers xv. 32–36. According to German nurses the day was not the Sabbath, but Sunday. Their tale runs as follows: 'Ages ago there went one Sunday an old man into the woods to hew sticks. He cut a faggot and slung it on a stout staff, cast it over his shoulder, and began to trudge home with his burthen. On his way he met a handsome man in Sunday suit, walking towards the church. The man stopped, and asked the faggot-bearer; "Do you know that this is Sunday on earth, when all must rest from their labours?" "Sunday on earth or Monday in heaven, it's all one to me?" laughed the wood-cutter. "Then bear your bundle for ever!" answered the stranger. "And as you value not Sunday on earth, yours shall be a perpetual Moon-day in heaven; you shall stand for eternity in the moon, a warning to all Sabbath-breakers." Thereupon the stranger vanished; and the man was caught up with his staff and faggot into the moon, where he stands yet.' According to some narrators the stranger was Christ; but whether from German laxity in such matters or for some other reason, no text is quoted in evidence, as by the more orthodox British nurses. Luke vi. 1–5 might serve.

48

Milton's opinion may be quoted against me here; and as received ideas respecting angels, good and bad, the fall of man, and many other such matters, are due quite as much to Milton as to any other authority, his opinion must not be lightly disregarded. But though, when Milton's Satan 'meets a vast vacuity' where his wings are of no further service to him,

'All unawaresFlutt'ring his pennons vain, plumb down he dropsTen thousand fathoms deep, and to this hourDown had been falling, had not by ill chanceThe strong rebuff of some tumultuous cloud,Instinct with fire and nitre, hurried himAs many miles aloft,'

yet this was written nearly a quarter of a century before Newton had established the law of gravity. Moreover, there is no evidence to show in what direction Satan fell; 'above is below and below above,' says Richter, 'to one stripped of gravitating body;' and whether Satan was under the influence of gravity or not, he would be practically exempt from its action when in the midst of that 'dark, illimitable ocean' of space,

'Without bound,Without dimensions, where length, breadth, and height,And time and place are lost.'

His lighting 'on Niphates' top,' and overleaping the gate of Paradise, may be used as arguments either way. On the whole, I must (according to my present lights) claim for Satan a freedom from all scientific restraints. This freedom is exemplified by his showing all the kingdoms of the world from an exceeding high mountain, thus affording the first practical demonstration of the flat-earth theory, the maintenance of which led to poor Mr. Hampden's incarceration.

49

The Sun itself claimed to have established the veracity of the account in a manner strongly recalling a well-known argument used by orthodox believers in the Bible account of the cosmogony. Either, say these, Moses discovered how the world was made, or the facts were revealed to him by some one who had made the discovery: but Moses could not have made the discovery, knowing nothing of the higher departments of science; therefore, the account came from the only Being who could rationally be supposed to know anything about the beginning of the world. 'Either,' said the New York Sun, speaking of a mathematical problem discussed in the article, 'that problem was predicated by us or some other person, who has thereby made the greatest of all modern discoveries in mathematical astronomy. We did not make it, for we know nothing of mathematics whatever; therefore, it was made by the only person to whom it can rationally be ascribed, namely Herschel the astronomer, its only avowed and undeniable author.' In reality, notwithstanding this convincing argument, the problem was stolen by Locke from a paper by Olbers, shortly before published, and gave the method followed by Beer and Mädler throughout their selenographical researches in 1833–37.

50

I had at the same time the good fortune to satisfy in equal degree, though quite unexpectedly, an English student of the sun, who at that time bore me no great good-will. Something in the article chanced to suggest that it came from another, presumably a rival, hand; while an essay which appeared about the same time (the spring of 1872) was commonly but erroneously attributed to me. Accordingly, a leading article in Nature was devoted to the annihilation of the writer supposed to be myself, and to the lavish and quite undeserved laudation of the article I had written, which was selected as typifying all the good qualities which an article of the kind should possess. Those acquainted with the facts were not a little amused by the mistake.

51

The Astronomer-Royal once told me that he had found that few persons have a clear conception of the fact that the stars rise and set. Still fewer know how the stars move, which stars rise and set, which are always above the horizon, which move on large circles, which on small ones; though a few hours' observation on half-a-dozen nights in the year (such observations being continuous, but made only at hourly intervals) would show dearly how the stars move. It is odd to find even some who write about astronomy making mistakes on matters so elementary. For instance, in a primer of astronomy recently published, it is stated that the stars which pass overhead in London rise and set on a slant—the real fact being that those stars never rise or set at all, never coming within some two dozen moon-breadths of the horizon.

52

In passing let me note that, of course, I am not discussing the arguments of paradoxists with the remotest idea of disproving them. They are not, in reality, worth the trouble. But they show where the general reader of astronomical text-books, and other such works, is likely to go astray, and thus conveniently indicate matters whose explanation may be useful or interesting.

53

Sterne anticipated this paradoxist in (jestingly) attributing glassiness to an inferior planet. He made the inhabitants, however, not the air, glassy. 'The intense heat of the country,' he says, speaking of the planet Mercury, 'must, I think, long ago have vitrified the bodies of the inhabitants to suit them for the climate; so that all the tenements of their souls may be nothing else, for aught the soundest philosophy can show to the contrary, but one fine transparent body of clear glass; so that till the inhabitant grows old and tolerably wrinkled, whereby the rays of light become monstrously refracted, or return reflected from the surface, etc., his soul might as well play the fool out o' doors as in her own house.'

54

It will be seen from Table X. of my treatise on Saturn that the ring disappeared on December 12, remaining invisible (because turning its dark side earthwards) till the spring of 1613. But on December 4, the ring must have been quite invisible in a telescope so feeble as Galileo's. The ring then would have been little more than a fine line of light as seen with one of our powerful modern telescopes.

55

North British Review for August 1860.

56

He had, indeed, at an earlier stage, shown a marvellous ignorance of astronomy by the remark, which doubtless appeared to him a safe one, that when he saw a planet on the sun in September he supposed it was Mercury; a September transit of Mercury being as impossible as an eclipse of the sun during the moon's third quarter.

57

It is, by the way, somewhat amusing to find Baron Humboldt referring a question of this sort to the great mathematician Gauss, and describing the problem as though it involved the most profound calculations. Ten minutes should suffice to deal with any problem of the kind.