TYCHO BRAHE.
The age following that of Copernicus produced three outstanding figures
associated with the science of astronomy, then reaching the close of
what Professor Forbes so aptly styles the geometrical period. These
three Sir David Brewster has termed "Martyrs of Science"; Galileo, the
great Italian philosopher, has his own place among the "Pioneers of
Science"; and invaluable though Tycho Brahe's work was, the latter can
hardly be claimed as a pioneer in the same sense as the other two.
Nevertheless, Kepler, the third member of the trio, could not have made
his most valuable discoveries without Tycho's observations.
Of noble family, born a twin on 14th December, 1546, at Knudstrup in
Scania (the southernmost part of Sweden, then forming part of the
kingdom of Denmark), Tycho was kidnapped a year later by a childless
uncle. This uncle brought him up as his own son, provided him at the age
of seven with a tutor, and sent him in 1559 to the University of
Copenhagen, to study for a political career by taking courses in
rhetoric and philosophy. On 21st August, 1560, however, a solar eclipse
took place, total in Portugal, and therefore of small proportions in
Denmark, and Tycho's keen interest was awakened, not so much by the
phenomenon, as by the fact that it had occurred according to prediction.
Soon afterwards he purchased an edition of Ptolemy in order to read up
the subject of astronomy, to which, and to mathematics, he devoted most
of the remainder of his three years' course at Copenhagen. His uncle
next sent him to Leipzig to study law, but he managed to continue his
astronomical researches. He obtained the Alphonsine and the new Prutenic
Tables, but soon found that the latter, though more accurate than the
former, failed to represent the true positions of the planets, and
grasped the fact that continuous observation was essential in order to
determine the true motions. He began by observing a conjunction of
Jupiter and Saturn in August, 1563, and found the Prutenic Tables
several days in error, and the Alphonsine a whole month. He provided
himself with a cross-staff for determining the angular distance between
stars or other objects, and, finding the divisions of the scale
inaccurate, constructed a table of corrections, an improvement that
seems to have been a decided innovation, the previous practice having
been to use the best available instrument and ignore its errors. About
this time war broke out between Denmark and Sweden, and Tycho returned
to his uncle, who was vice-admiral and attached to the king's suite. The
uncle died in the following month, and early in the next year Tycho went
abroad again, this time to Wittenberg. After five months, however, an
outbreak of plague drove him away, and he matriculated at Rostock, where
he found little astronomy but a good deal of astrology. While there he
fought a duel in the dark and lost part of his nose, which he replaced
by a composition of gold and silver. He carried on regular observations
with his cross-staff and persevered with his astronomical studies in
spite of the objections and want of sympathy of his fellow-countrymen.
The King of Denmark, however, having a higher opinion of the value of
science, promised Tycho the first canonry that should fall vacant in the
cathedral chapter of Roskilde, so that he might be assured of an income
while devoting himself to financially unproductive work. In 1568 Tycho
left Rostock, and matriculated at Basle, but soon moved on to Augsburg,
where he found more enthusiasm for astronomy, and induced one of his new
friends to order the construction of a large 19-foot quadrant of heavy
oak beams. This was the first of the series of great instruments
associated with Tycho's name, and it remained in use for five years,
being destroyed by a great storm in 1574. Tycho meanwhile had left
Augsburg in 1570 and returned to live with his father, now governor of
Helsingborg Castle, until the latter's death in the following year.
Tycho then joined his mother's brother, Steen Bille, the only one of his
relatives who showed any sympathy with his desire for a scientific
career.
On 11th November, 1572, Tycho noticed an unfamiliar bright star in the
constellation of Cassiopeia, and continued to observe it with a sextant.
It was a very brilliant object, equal to Venus at its brightest for the
rest of November, not falling below the first magnitude for another four
months, and remaining visible for more than a year afterwards. Tycho
wrote a little book on the new star, maintaining that it had practically
no parallax, and therefore could not be, as some supposed, a comet.
Deeming authorship beneath the dignity of a noble he was very reluctant
to publish, but he was convinced of the importance of increasing the
number and accuracy of observations, though he was by no means free from
all the erroneous ideas of his time. The little book contained a certain
amount of astrology, but Tycho evidently did not regard this as of very
great importance. He adopted the view that the very rarity of the
phenomenon of a new star must prevent the formulation and adoption of
definite rules for determining its significance. We gather from lectures
which he was persuaded to deliver at the University of Copenhagen that,
though in agreement with the accepted canons of astrology as to the
influence of planetary conjunctions and such phenomena on the course of
human events, he did not consider the fate predicted by anyone's
horoscope to be unavoidable, but thought the great value of astrology
lay in the warnings derived from such computations, which should enable
the believer to avoid threatened calamities. In 1575 he left Denmark
once more and made his way to Cassel, where he found a kindred spirit in
the studious Landgrave, William IV. of Hesse, whose astronomical
pursuits had been interrupted by his accession to the government of
Hesse, in 1567. Tycho observed with him for some time, the two forming a
firm friendship, and then visited successively Frankfort, Basle, and
Venice, returning by way of Augsburg, Ratisbon, and Saalfeld to
Wittenberg; on the way he acquired various astronomical manuscripts,
made friends among practical astronomers, and examined new instruments.
He seemed to have considered the advantages of the several places thus
visited and decided on Basle, but on his return to Denmark to fetch his
family with the object of transferring them to Basle, he found that his
friend the Landgrave had written to King Frederick on his behalf,
urging him to provide the means to enable Tycho to pursue his
astronomical work, promising that not only should credit result for the
king and for Denmark but that science itself would be greatly advanced.
The ultimate result of this letter was that after refusing various
offers, Tycho accepted from the king a grant of the small island of
Hveen, in the Sound, with a guaranteed income, in addition to a large
sum from the treasury for building an observatory on the island, far
removed from the distractions of court life. Here Tycho built his
celebrated observatory of Uraniborg and began observations in December,
1576, using the large instruments then found necessary in order to
attain the accuracy of observation which within the next half-century
was to be so greatly facilitated by the invention of the telescope. Here
also he built several smaller observing rooms, so that his pupils should
be able to observe independently. For more than twenty years he
continued his observations at Uraniborg, surrounded by his family, and
attracting numerous pupils. His constant aim was to accumulate a large
store of observations of a high order of accuracy, and thus to provide
data for the complete reform of astronomy. As we have seen, few of the
Danish nobles had any sympathy with Tycho's pursuits, and most of them
strongly resented the continual expense borne by the King's treasury.
Tycho moreover was so absorbed in his scientific pursuits that he would
not take the trouble to be a good landlord, nor to carry out all the
duties laid upon him in return for certain of his grants of income. His
buildings included a chemical laboratory, and he was in the habit of
making up elixirs for various medical purposes; these were quite
popular, particularly as he made no charge for them. He seems to have
been something of a homoeopathist, for he recommends sulphur to cure
infectious diseases "brought on by the sulphurous vapours of the Aurora
Borealis"!
King Frederick, in consideration of various grants to Tycho, relied
upon his assistance in scientific matters, and especially in
astrological calculations; such as the horoscope of the heir apparent,
Prince Christian, born in 1577, which has been preserved among Tycho's
writings. There is, however, no known copy in existence of any of the
series of annual almanacs with predictions which he prepared for the
King. In November, 1577, appeared a bright comet, which Tycho carefully
observed with his sextant, proving that it had no perceptible parallax,
and must therefore be further off than the moon. He thus definitely
overthrew the common belief in the atmospheric origin of comets, which
he had himself hitherto shared. With increasing accuracy he observed
several other comets, notably one in 1585, when he had a full equipment
of instruments and a large staff of assistants. The year 1588, which saw
the death of his royal benefactor, saw also the publication of a volume
of Tycho's great work "Introduction to the New Astronomy". The first
volume, devoted to the new star of 1572, was not ready, because the
reduction of the observations involved so much research to correct the
star places for refraction, precession, etc.; it was not completed in
fact until Tycho's death, but the second volume, dealing with the comet
of 1577, was printed at Uraniborg and some copies were issued in 1588.
Besides the comet observations it included an account of Tycho's system
of the world. He would not accept the Copernican system, as he
considered the earth too heavy and sluggish to move, and also that the
authority of Scripture was against such an hypothesis. He therefore
assumed that the other planets revolved about the sun, while the sun,
moon, and stars revolved about the earth as a centre. Geometrically this
is much the same as the Copernican system, but physically it involves
the grotesque demand that the whole system of stars revolves round our
insignificant little earth every twenty-four hours. Since his previous
small book on the comet, Tycho had evidently considered more fully its
possible astrological significance, for he foretold a religious war,
giving the date of its commencement, and also the rising of a great
Protestant champion. These predictions were apparently fulfilled almost
to the letter by the great religious wars that broke out towards the end
of the sixteenth century, and in the person of Gustavus Adolphus.
King Frederick's death did not at first affect Tycho's position, for the
new king, Christian, was only eleven years old, and for some years the
council of regents included two of his supporters. After their deaths,
however, his emoluments began to be cut down on the plea of economy, and
as he took very little trouble to carry out any other than scientific
duties it was easy enough for his enemies to find fault. One after
another source of income was cut off, but he persevered with his
scientific work, including a catalogue of stars. He had obtained plenty
of good observations of 777 stars, but thought his catalogue should
contain 1000 stars, so he hastily observed as many more as he could up
to the time of his leaving Hveen, though even then he had not completed
his programme. About the time that King Christian reached the age of
eighteen, Tycho began to look about for a new patron, and to consider
the prospects offered by transferring himself with his instruments and
activities to the patronage of the Emperor Rudolph II. In 1597, when
even his pension from the Royal treasury was cut off, he hurriedly
packed up his instruments and library, and after a few weeks' sojourn at
Copenhagen, proceeded to Rostock, in Mecklenburg, whence he sent an
appeal to King Christian. It is possible that had he done this before
leaving Hveen it might have had more effect, but it can be readily seen
from the tone of the king's unfavourable reply that his departure was
regarded as an aggravation of previous shortcomings. Driven from Rostock
by the plague, Tycho settled temporarily at Wandsbeck, in Holstein, but
towards the end of 1598 set out to meet the Emperor at Prague. Once
more plague intervened and he spent some time at Dresden, afterwards
going to Wittenberg for the winter. He ultimately reached Prague in
June, 1599. Rudolph granted him a salary of at least 3000 florins,
promising also to settle on him the first hereditary estate that should
lapse to the Crown. He offered, moreover, the choice between three
castles outside Prague, of which Tycho chose Benatek. There he set about
altering the buildings in readiness for his instruments, for which he
sent to Uraniborg. Before they reached him, after many vexatious delays,
he had given up waiting for the funds promised for his building
expenses, and removed from Benatek to Prague. It was during this
interval that after considerable negotiation, Kepler, who had been in
correspondence with Tycho, consented to join him as an assistant.
Another assistant, Longomontanus, who had been with Tycho at Uraniborg,
was finding difficulty with the long series of Mars observations, and it
was arranged that he should transfer his energies to the lunar
observations, leaving those of Mars for Kepler. Before very much could
be done with them, however, Tycho died at the end of October, 1601. He
may have regretted the peaceful island of Hveen, considering the
troubles in which Bohemia was rapidly becoming involved, but there is
little doubt that had it not been for his self-imposed exile, his
observations would not have come into Kepler's hands, and their great
value might have been lost. In any case it was at Uraniborg that the
mass of observations was produced upon which the fame of Tycho Brahe
rests. His own discoveries, though in themselves the most important made
in astronomy for many centuries, are far less valuable than those for
which his observations furnished the material. He discovered the third
and fourth inequalities of the moon in longitude, called respectively
the variation and the annual equation, also the variability of the
motion of the moon's nodes and the inclination of its orbit to the
ecliptic. He obtained an improved value of the constant of precession,
and did good service by rejecting the idea that it was variable, an idea
which, under the name of trepidation, had for many centuries been
accepted. He discovered the effect of refraction, though only
approximately its amount, and determined improved values of many other
astronomical constants, but singularly enough made no determination of
the distance of the sun, adopting instead the ancient and erroneous
value given by Hipparchus.
His magnificent Observatory of Uraniborg, the finest building for
astronomical purposes that the world had hitherto seen, was allowed to
fall into decay, and scarcely more than mere indications of the site may
now be seen.