Part 2 (1/2)
Before Tycho was seventeen he had commenced the difficult task of calculating the movements of the planets and the places which they occupied on the sky from time to time. He was not a little surprised to find that the actual positions of the planets differed very widely from those which were a.s.signed to them by calculations from the best existing works of astronomers. With the insight of genius he saw that the only true method of investigating the movements of the heavenly bodies would be to carry on a protracted series of measurements of their places. This, which now seems to us so obvious, was then entirely new doctrine. Tycho at once commenced regular observations in such fas.h.i.+on as he could. His first instrument was, indeed, a very primitive one, consisting of a simple pair of compa.s.ses, which he used in this way. He placed his eye at the hinge, and then opened the legs of the compa.s.s so that one leg pointed to one star and the other leg to the other star. The compa.s.s was then brought down to a divided circle, by which means the number of degrees in the apparent angular distance of the two stars was determined.
His next advance in instrumental equipment was to provide himself with the contrivance known as the ”cross-staff,” which he used to observe the stars whenever opportunity offered. It must, of course, be remembered that in those days there were no telescopes. In the absence of optical aid, such as lenses afford the modern observers, astronomers had to rely on mechanical appliances alone to measure the places of the stars. Of such appliances, perhaps the most ingenious was one known before Tycho's time, which we have represented in the adjoining figure.
[PLATE: TYCHO'S CROSS STAFF.]
Let us suppose that it be desired to measure the angle between two stars, then if the angle be not too large it can be determined in the following manner. Let the rod AB be divided into inches and parts of an inch, and let another rod, CD, slide up and down along AB in such a way that the two always remain perpendicular to each other.
”Sights,” like those on a rifle, are placed at A and C, and there is a pin at D. It will easily be seen that, by sliding the movable bar along the fixed one, it must always be possible when the stars are not too far apart to bring the sights into such positions that one star can be seen along DC and the other along DA. This having been accomplished, the length from A to the cross-bar is read off on the scale, and then, by means of a table previously prepared, the value of the required angular distance is obtained. If the angle between the two stars were greater than it would be possible to measure in the way already described, then there was a provision by which the pin at D might be moved along CD into some other position, so as to bring the angular distance of the stars within the range of the instrument.
[PLATE: TYCHO'S ”NEW STAR” s.e.xTANT OF 1572.
(The arms, of walnut wood, are about 5 1/2 ft. long.)]
No doubt the cross-staff is a very primitive contrivance, but when handled by one so skilful as Tycho it afforded results of considerable accuracy. I would recommend any reader who may have a taste for such pursuits to construct a cross-staff for himself, and see what measurements he can accomplish with its aid.
To employ this little instrument Tycho had to evade the vigilance of his conscientious tutor, who felt it his duty to interdict all such occupations as being a frivolous waste of time. It was when Vedel was asleep that Tycho managed to escape with his cross staff and measure the places of the heavenly bodies. Even at this early age Tycho used to conduct his observations on those thoroughly sound principles which lie at the foundation of all accurate modern astronomy. Recognising the inevitable errors of workmans.h.i.+p in his little instrument, he ascertained their amount and allowed for their influence on the results which he deduced. This principle, employed by the boy with his cross-staff in 1564, is employed at the present day by the Astronomer Royal at Greenwich with the most superb instruments that the skill of modern opticians has been able to construct.
[PLATE: TYCHO'S TRIGONIC s.e.xTANT.
(The arms, AB and AC, are about 5 1/2 ft. long.)]
After the death of his uncle, when Tycho was nineteen years of age, it appears that the young philosopher was no longer interfered with in so far as the line which his studies were to take was concerned.
Always of a somewhat restless temperament, we now find that he s.h.i.+fted his abode to the University of Rostock, where he speedily made himself notable in connection with an eclipse of the moon on 28th October, 1566. Like every other astronomer of those days, Tycho had always a.s.sociated astronomy with astrology. He considered that the phenomena of the heavenly bodies always had some significance in connection with human affairs. Tycho was also a poet, and in the united capacity of poet, astrologer, and astronomer, he posted up some verses in the college at Rostock announcing that the lunar eclipse was a prognostication of the death of the great Turkish Sultan, whose mighty deeds at that time filled men's minds. Presently news did arrive of the death of the Sultan, and Tycho was accordingly triumphant; but a little later it appeared that the decease had taken place BEFORE the eclipse, a circ.u.mstance which caused many a laugh at Tycho's expense.
[PLATE: TYCHO'S ASTRONOMIC s.e.xTANT.
(Made of steel: the arms, AB, AC, measure 4 ft.)
PLATE: TYCHO'S EQUATORIAL ARMILLARY.
(The meridian circle, E B C A D, made of solid steel, is nearly 6 ft. in diameter.)]
Tycho being of a somewhat turbulent disposition, it appears that, while at the University of Rostock, he had a serious quarrel with another Danish n.o.bleman. We are not told for certain what was the cause of the dispute. It does not, however, seem to have had any more romantic origin than a difference of opinion as to which of them knew the more mathematics. They fought, as perhaps it was becoming for two astronomers to fight, under the canopy of heaven in utter darkness at the dead of night, and the duel was honourably terminated when a slice was taken off Tycho's nose by the insinuating sword of his antagonist. For the repair of this injury the ingenuity of the great instrument-maker was here again useful, and he made a subst.i.tute for his nose ”with a composition of gold and silver.” The imitation was so good that it is declared to have been quite equal to the original. Dr. Lodge, however, pointedly observes that it does not appear whether this remark was made by a friend or an enemy.
[PLATE: THE GREAT AUGSBURG QUADRANT.
(Built of heart of oak; the radii about 19 ft.)
PLATE: TYCHO'S ”NEW SCHEME OF THE TERRESTRIAL SYSTEM,” 1577.]
The next few years Tycho spent in various places ardently pursuing somewhat varied branches of scientific study. At one time we hear of him a.s.sisting an astronomical alderman, in the ancient city of Augsburg, to erect a tremendous wooden machine--a quadrant of 19-feet radius--to be used in observing the heavens. At another time we learn that the King of Denmark had recognised the talents of his ill.u.s.trious subject, and promised to confer on him a pleasant sinecure in the shape of a canonry, which would a.s.sist him with the means for indulging his scientific pursuits. Again we are told that Tycho is pursuing experiments in chemistry with the greatest energy, nor is this so incompatible as might at first be thought with his devotion to astronomy. In those early days of knowledge the different sciences seemed bound together by mysterious bonds.
Alchemists and astrologers taught that the several planets were correlated in some mysterious manner with the several metals. It was, therefore hardly surprising that Tycho should have included a study of the properties of the metals in the programme of his astronomical work.
[PLATE: URANIBORG AND ITS GROUNDS.
PLATE: GROUND-PLAN OF THE OBSERVATORY.]
An event, however, occurred in 1572 which stimulated Tycho's astronomical labours, and started him on his life's work. On the 11th of November in that year, he was returning home to supper after a day's work in his laboratory, when he happened to lift his face to the sky, and there he beheld a brilliant new star. It was in the constellation of Ca.s.siopeia, and occupied a position in which there had certainly been no bright star visible when his attention had last been directed to that part of the heavens. Such a phenomenon was so startling that he found it hard to trust the evidence of his senses.
He thought he must be the subject of some hallucination. He therefore called to the servants who were accompanying him, and asked them whether they, too, could see a brilliant object in the direction in which he pointed. They certainly could, and thus he became convinced that this marvellous object was no mere creation of the fancy, but a veritable celestial body--a new star of surpa.s.sing splendour which had suddenly burst forth. In these days of careful scrutiny of the heavens, we are accustomed to the occasional outbreak of new stars. It is not, however, believed that any new star which has ever appeared has displayed the same phenomenal brilliance as was exhibited by the star of 1572.
This object has a value in astronomy far greater than it might at first appear. It is true, in one sense, that Tycho discovered the new star, but it is equally true, in a different sense, that it was the new star which discovered Tycho. Had it not been for this opportune apparition, it is quite possible that Tycho might have found a career in some direction less beneficial to science than that which he ultimately pursued.