Great Astronomers by Robert Stawell Ball (best ereader for students .txt) 📖

any kind were but few and scarce,

and scientific books were especially unattainable. It so

happened, however, that a Latin version of Ptolemy’s astronomical

works had appeared a few years before the eclipse took place, and

Tycho managed to buy a copy of this book, which was then the chief

authority on celestial matters. Young as the boy astronomer was,

he studied hard, although perhaps not always successfully, to

understand Ptolemy, and to this day his copy of the great work,

copiously annotated and marked by the schoolboy hand, is preserved

as one of the chief treasures in the library of the University at

Prague.

 

After Tycho had studied for about three years at the University of

Copenhagen, his uncle thought it would be better to send him, as

was usual in those days, to complete his education by a course of

study in some foreign university. The uncle cherished the hope

that in this way the attention of the young astronomer might be

withdrawn from the study of the stars and directed in what

appeared to him a more useful way. Indeed, to the wise heads of

those days, the pursuit of natural science seemed so much waste of

good time which might otherwise be devoted to logic or rhetoric or

some other branch of study more in vogue at that time. To assist

in this attempt to wean Tycho from his scientific tastes, his

uncle chose as a tutor to accompany him an intelligent and upright

young man named Vedel, who was four years senior to his pupil, and

accordingly, in 1562, we find the pair taking up their abode at

the University of Leipzig.

 

The tutor, however, soon found that he had undertaken a most

hopeless task. He could not succeed in imbuing Tycho with the

slightest taste for the study of the law or the other branches of

knowledge which were then thought so desirable. The stars, and

nothing but the stars, engrossed the attention of his pupil. We

are told that all the money he could obtain was spent secretly in

buying astronomical books and instruments. He learned the name of

the stars from a little globe, which he kept hidden from Vedel,

and only ventured to use during the latter’s absence. No little

friction was at first caused by all this, but in after years a

fast and enduring friendship grew up between Tycho and his tutor,

each of whom learned to respect and to love the other.

 

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 assigned 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

fashion as he could. His first instrument was, indeed, a very

primitive one, consisting of a simple pair of compasses, which

he used in this way. He placed his eye at the hinge, and then

opened the legs of the compass so that one leg pointed to one

star and the other leg to the other star. The compass 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” SEXTANT 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

workmanship 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 SEXTANT.

(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 shifted 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 associated 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 circumstance which

caused many a laugh at Tycho’s expense.

 

[PLATE: TYCHO’S ASTRONOMIC SEXTANT.

(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 nobleman. 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 substitute 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 assisting 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 illustrious subject, and promised to confer on him a

pleasant sinecure in the shape of a canonry, which would assist

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 Cassiopeia, 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 surpassing splendour which

had suddenly burst forth. In