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GREAT ASTRONOMERS

 

By

 

SIR ROBERT S. BALL D.Sc. LL.D. F.R.S.

 

Lowndean Professor of Astronomy and Geometry in the

University of Cambridge

 

Author of “In Starry Realms” ” In the High Heavens” etc.

 

[PLATE: GREENWICH OBSERVATORY.]

 

PREFACE.

 

It has been my object in these pages to present the life of each

astronomer in such detail as to enable the reader to realise in

some degree the man’s character and surroundings; and I have

endeavoured to indicate as clearly as circumstances would permit

the main features of the discoveries by which he has become known.

 

There are many types of astronomers—from the stargazer who merely

watches the heavens, to the abstract mathematician who merely

works at his desk; it has, consequently, been necessary in the

case of some lives to adopt a very different treatment from that

which seemed suitable for others.

 

While the work was in progress, some of the sketches appeared in

“Good Words.” The chapter on Brinkley has been chiefly derived from

an article on the “History of Dunsink Observatory,” which was

published on the occasion of the tercentenary celebration of the

University of Dublin in 1892, and the life of Sir William Rowan

Hamilton is taken, with a few alterations and omissions, from an

article contributed to the “Quarterly Review” on Graves’ life of

the great mathematician. The remaining chapters now appear for

the first time. For many of the facts contained in the sketch of

the late Professor Adams, I am indebted to the obituary notice

written by my friend Dr. J.W.L. Glaisher, for the Royal Astronomical

Society; while with regard to the late Sir George Airy, I have a

similar acknowledgment to make to Professor H.H. Turner. To my

friend Dr. Arthur A. Rambaut I owe my hearty thanks for his

kindness in aiding me in the revision of the work.

 

R.S.B.

The Observatory, Cambridge.

October, 1895

 

CONTENTS.

 

INTRODUCTION.

 

PTOLEMY.

 

COPERNICUS.

 

TYCHO BRAHE.

 

GALILEO.

 

KEPLER.

 

ISAAC NEWTON.

 

FLAMSTEED.

 

HALLEY.

 

BRADLEY.

 

WILLIAM HERSCHEL.

 

LAPLACE.

 

BRINKLEY.

 

JOHN HERSCHEL.

 

THE EARL OF ROSSE.

 

AIRY.

 

HAMILTON.

 

LE VERRIER.

 

ADAMS.

 

LIST OF ILLUSTRATIONS.

 

THE OBSERVATORY, GREENWICH.

 

PTOLEMY.

 

PTOLEMY’S PLANETARY SCHEME.

 

PTOLEMY’S THEORY OF THE MOVEMENT OF MARS.

 

THORN, FROM AN OLD PRINT.

 

COPERNICUS.

 

FRAUENBURG, FROM AN OLD PRINT.

 

EXPLANATION OF PLANETARY MOVEMENTS.

 

TYCHO BRAHE.

 

TYCHO’S CROSS STAFF.

 

TYCHO’S “NEW STAR” SEXTANT OF 1572.

 

TYCHO’S TRIGONIC SEXTANT.

 

TYCHO’S ASTRONOMIC SEXTANT.

 

TYCHO’S EQUATORIAL ARMILLARY.

 

THE GREAT AUGSBURG QUADRANT.

 

TYCHO’S “NEW SCHEME OF THE TERRESTRIAL SYSTEM,” 1577.

 

URANIBORG AND ITS GROUNDS.

 

GROUND-PLAN OF THE OBSERVATORY.

 

THE OBSERVATORY OF URANIBORG, ISLAND OF HVEN.

 

EFFIGY ON TYCHO’S TOMB AT PRAGUE.

By Permission of Messrs. A. & C. Black.

 

TYCHO’S MURAL QUADRANT, URANIBORG.

 

GALILEO’S PENDULUM.

 

GALILEO.

 

THE VILLA ARCETRI.

 

FACSIMILE SKETCH OF LUNAR SURFACE BY GALILEO.

 

CREST OF GALILEO’S FAMILY.

 

KEPLER’S SYSTEM OF REGULAR SOLIDS.

 

KEPLER.

 

SYMBOLICAL REPRESENTATION OF THE PLANETARY SYSTEM.

 

THE COMMEMORATION OF THE RUDOLPHINE TABLES.

 

WOOLSTHORPE MANOR.

 

TRINITY COLLEGE, CAMBRIDGE.

 

DIAGRAM OF A SUNBEAM.

 

ISAAC NEWTON.

 

SIR ISAAC NEWTON’S LITTLE REFLECTOR.

 

SIR ISAAC NEWTON’S SUN-DIAL.

 

SIR ISAAC NEWTON’S TELESCOPE.

 

SIR ISAAC NEWTON’S ASTROLABE.

 

SIR ISAAC NEWTON’S SUN-DIAL IN THE ROYAL SOCIETY.

 

FLAMSTEED’S HOUSE.

 

FLAMSTEED.

 

HALLEY.

 

GREENWICH OBSERVATORY IN HALLEY’S TIME.

 

7, NEW KING STREET, BATH.

From a Photograph by John Poole, Bath.

 

WILLIAM HERSCHEL.

 

CAROLINE HERSCHEL.

 

STREET VIEW, HERSCHEL HOUSE, SLOUGH.

From a Photograph by Hill & Saunders, Eton.

 

GARDEN VIEW, HERSCHEL HOUSE, SLOUGH.

From a Photograph by Hill & Saunders, Eton.

 

OBSERVATORY, HERSCHEL HOUSE, SLOUGH.

From a Photograph by Hill & Saunders, Eton.

 

THE 40-FOOT TELESCOPE, HERSCHEL HOUSE, SLOUGH.

From a Photograph by Hill & Saunders, Eton.

 

LAPLACE.

 

THE OBSERVATORY, DUNSINK.

From a Photograph by W. Lawrence, Dublin.

 

ASTRONOMETER MADE BY SIR JOHN HERSCHEL.

 

SIR JOHN HERSCHEL.

 

NEBULA IN SOUTHERN HEMISPHERE.

 

THE CLUSTER IN THE CENTAUR.

 

OBSERVATORY AT FELDHAUSEN.

 

GRANITE COLUMN AT FELDHAUSEN.

 

THE EARL OF ROSSE.

 

BIRR CASTLE.

From a Photograph by W. Lawrence, Dublin.

 

THE MALL, PARSONSTOWN.

From a Photograph by W. Lawrence, Dublin.

 

LORD ROSSE’S TELESCOPE.

From a Photograph by W. Lawrence, Dublin.

 

ROMAN CATHOLIC CHURCH, PARSONSTOWN.

From a Photograph by W. Lawrence, Dublin.

 

AIRY.

From a Photograph by E.P. Adams, Greenwich.

 

HAMILTON.

 

ADAMS.

 

THE OBSERVATORY, CAMBRIDGE.

 

INTRODUCTION.

 

Of all the natural sciences there is not one which offers such

sublime objects to the attention of the inquirer as does the

science of astronomy. From the earliest ages the study of the

stars has exercised the same fascination as it possesses at the

present day. Among the most primitive peoples, the movements of

the sun, the moon, and the stars commanded attention from their

supposed influence on human affairs.

 

The practical utilities of astronomy were also obvious in primeval

times. Maxims of extreme antiquity show how the avocations of the

husbandman are to be guided by the movements of the heavenly

bodies. The positions of the stars indicated the time to plough,

and the time to sow. To the mariner who was seeking a way across

the trackless ocean, the heavenly bodies offered the only reliable

marks by which his path could be guided. There was, accordingly,

a stimulus both from intellectual curiosity and from practical

necessity to follow the movements of the stars. Thus began a

search for the causes of the ever-varying phenomena which the

heavens display.

 

Many of the earliest discoveries are indeed prehistoric. The

great diurnal movement of the heavens, and the annual revolution

of the sun, seem to have been known in times far more ancient than

those to which any human monuments can be referred. The acuteness

of the early observers enabled them to single out the more

important of the wanderers which we now call planets. They saw

that the star-like objects, Jupiter, Saturn, and Mars, with the

more conspicuous Venus, constituted a class of bodies wholly

distinct from the fixed stars among which their movements lay, and

to which they bear such a superficial resemblance. But the

penetration of the early astronomers went even further, for they

recognized that Mercury also belongs to the same group, though

this particular object is seen so rarely. It would seem that

eclipses and other phenomena were observed at Babylon from a very

remote period, while the most ancient records of celestial

observations that we possess are to be found in the Chinese

annals.

 

The study of astronomy, in the sense in which we understand the

word, may be said to have commenced under the reign of the

Ptolemies at Alexandria. The most famous name in the science of

this period is that of Hipparchus who lived and worked at Rhodes

about the year 160BC. It was his splendid investigations that

first wrought the observed facts into a coherent branch of

knowledge. He recognized the primary obligation which lies on the

student of the heavens to compile as complete an inventory as

possible of the objects which are there to be found. Hipparchus

accordingly commenced by undertaking, on a small scale, a task

exactly similar to that on which modern astronomers, with all

available appliances of meridian circles, and photographic

telescopes, are constantly engaged at the present day. He

compiled a catalogue of the principal fixed stars, which is of

special value to astronomers, as being the earliest work of its

kind which has been handed down. He also studied the movements of

the sun and the moon, and framed theories to account for the

incessant changes which he saw in progress. He found a much more

difficult problem in his attempt to interpret satisfactorily the

complicated movements of the planets. With the view of

constructing a theory which should give some coherent account of

the subject, he made many observations of the places of these

wandering stars. How great were the advances which Hipparchus

accomplished may be appreciated if we reflect that, as a

preliminary task to his more purely astronomical labours, he had

to invent that branch of mathematical science by which alone the

problems he proposed could be solved. It was for this purpose

that he devised the indispensable method of calculation which we

now know so well as trigonometry. Without the aid rendered by

this beautiful art it would have been impossible for any really

important advance in astronomical calculation to have been

effected.

 

But the discovery which shows, beyond all others, that Hipparchus

possessed one of the master-minds of all time was the detection of

that remarkable celestial movement known as the precession of the

equinoxes. The inquiry which conducted to this discovery involved

a most profound investigation, especially when it is remembered

that in the days of Hipparchus the means of observation of the

heavenly bodies were only of the rudest description, and the

available observations of earlier dates were extremely scanty.

We can but look with astonishment on the genius of the man who, in

spite of such difficulties, was able to detect such a phenomenon

as the precession, and to exhibit its actual magnitude. I shall

endeavour to explain the nature of this singular celestial

movement, for it may be said to offer the first instance in the

history of science in which we find that combination of accurate

observation with skilful interpretation, of which, in the

subsequent development of astronomy, we have so many splendid

examples.

 

The word equinox implies the condition that the night is equal to

the day. To a resident on the equator the night is no doubt equal

to the day at all times in the year, but to one who lives on any

other part of the earth, in either hemisphere, the night and the

day are not generally equal. There is, however, one occasion in

spring, and another in autumn, on which the day and the night are

each twelve hours at all places on the earth. When the night and

day are equal in spring, the point which the sun occupies on the

heavens is termed the vernal equinox. There is similarly another

point in which the sun is situated at the time of the autumnal

equinox. In any investigation of the celestial movements the

positions of these two equinoxes on the heavens are of primary

importance, and Hipparchus, with the instinct of genius, perceived

their significance, and commenced to study them. It will be

understood that we can always define the position of a point on

the sky with reference to the surrounding stars. No doubt we do

not see the stars near the sun when the sun is shining, but they

are there nevertheless. The ingenuity of Hipparchus enabled him

to determine the positions of each of the two equinoxes relatively

to the stars which lie in its immediate vicinity. After

examination of the celestial places of these points at different

periods, he was led to the conclusion that each equinox was moving

relatively to the stars, though that movement was so slow that

twenty five