BRIEF BIOGRAPHY OF TYCHO BRÄHE

In contrast to Copernicus, Tycho Brähe is not remembered through a single, important discovery. He was, however, a supreme observer; possibly unsurpassed throughout the history of astronomy. It is therefore sadly ironical that such a gifted observational astronomer died about a decade before the telescope became popular; surely, his discoveries and measurements would have been even more astounding. Although by modern standards the positions of the 777 stars that he catalogued are of relatively low accuracy, let us not forget he used crude, clumsy naked-eye instruments. Again, in contrast to Copernicus, Brähe was a larger than life character; his life could even be described as bizarre! Like most of his contemporaries he was deeply convinced of the truth of astrological doctrines and he often determined horoscopes. However, he thought astrology involved much more than predictions; that it was also a science that involved knowledge of the inner unity of the world.

Tyge (or Tycho [1]) Brähe was born on December 14, 1546 at Knudstrup in Skaane (then Danish but now in Sweden). He was of noble blood; his father Otto was Governor of Helsingborg Castle. Tycho was the eldest son, and the second of five (surviving) children [2]. For some reason his father had promised his brother Jørgen, who was an officer in the Danish Navy, that as soon as another son was born, Tycho would be handed over to Jørgen to be brought up by him. When the next boy was born Tycho's mother, Beate, reneged on the deal and so Jørgen actually kidnapped Tycho. The background and story is somewhat unclear but it appears that Tycho did indeed spend his youth at Jørgen's home at Torstrup rather than with Beate and Otto; apparently, some sort of amicable agreement was made. Little is known about his early life. In 1559 he went to University in Copenhagen and while there, on August 21, 1560, he witnessed a partial eclipse of the Sun, which seemed to have a lasting impression on the young boy.

His uncle wanted him to be a diplomat with proper political connections and so he decided to send him to Leipzig and have him study law. Clearly, he wasn't convinced of Tycho's commitment to his studies as he arranged for Anders Vedel to watch over him - acting as a traveling companion and guardian - while he was in Leipzig. (Apparently, Jørgen had come across a Latin translation of Ptolemy's Almagest that the young Tycho had purchased while in Copenhagen!) It could not have been easy for Vedel for he was only four years older than Tycho. In addition, he was sensible enough to realize that he could cut Tycho off from astronomy altogether. The arrangement they came to was that Tycho would study law during the day and study the stars at night. It was certain that Tycho cheated on this bargain by carrying out secret observation when Vedel was asleep! Eventually, Anders and Tycho became good friends.

In 1563 an astronomical event occurred that could be described as a 'watershed' for Tycho. There was a conjunction of the planets Jupiter and Saturn, i.e., when they appeared side-by-side in the sky (of course, in reality this was an illusion since Jupiter is much closer to Earth than Saturn); but on August 24 the two planets appeared to merge into a single source of light. Events like this could be predicted from published astronomical tables, for example the Alphonsine Tables, which were based on Ptolemy's model [3], and Reinhold's Prutenic Tables of 1551, which were based on Copernicus' model. The former Tables gave a date for the conjunction that was in error by one month and the latter Tables, although they were an improvement, by several days. He made what turned out to be his first observations on record by using a pair of compasses. He held the center to one eye and pointed the arms at Jupiter and Saturn and determined the angular distance between them by comparing the separation of the arms to a circle divided into degrees. Crude methods like this did not appeal to him and so he started making more accurate instruments although he was officially studying law and astronomy was supposed only to be a hobby. (You see, Tycho was a firm believed in astrology and in the unity of the entire world. It was clear to him that the discrepancies in the astronomical tables gave rise to great concerns ... How was it possible to make reliable judgments on the connections between celestial and Earthly events? Clearly, a much better knowledge of planetary motions was necessary, which could be obtained only by new observations with improved instruments.)

In 1565 Jørgen Brähe requested that Tycho and Anders return home; war had broken out between Denmark and Sweden. Tycho was probably pleased to leave Leipzig because the more he studied law the less he liked it. Shortly after their return, Jørgen Brähe died in unusual circumstances [4]. Tycho, although very upset at the death of his uncle, now realized that there was no reason for his to remain in Denmark nor to study law. Another uncle, Steen Bille, advised the young man - he was still a teenager - to settle his affairs in Denmark - he had inherited some property on the death of Jørgen - and return to Germany to study whatever he was interested in.

Tycho first went to Wittenberg and then Rostock, where he had a disagreement with another Danish nobleman that had a somewhat humorous outcome. Apparently, at a party held by one of the professors around Christmas 1566, he quarreled with Manderup Parbsjerg over who was the better mathematician and a week later, in the best tradition of mediaeval knights they fought a duel. Tycho appears to have come off worse by having a bad wound to his nose! However, he made a 'cover' for his nose of gold, silver and wax , which he wore for the rest of his life! Some of the later pictures of Tycho - like the engraving shown here - indicate that the wound was to the bridge of his nose.

In 1569 Tycho visited Augsburg where the first of his large measuring instruments was devised, principally with the help of Paul and Johann Hainzel, who were members of the town council and amateur astronmers. One of the instruments was a quadrant, made of oak, with a radius of 19 feet used mainly for measuring the angular height of stars to an alledged accuracy of about 0.003o, but hardly portable. The other was a sextant, with a sector of 30o, for measuring the angle between stars [5]. (The quadrant proved to be very significant and was used for making measurements of 'Tycho's star' in 1572 - see below. It was destroyed in a storm in 1574.)

Tycho returned to Denmark in 1571 as his father was dying. He remained after the funeral for a while at his uncle's estate, where it appears that he took more than a passing interest in chemistry, i.e., alchemy. But in 1572 he made an astronomical observation that made him famous; he was well aware of the positions of stars but on November 11 he saw a 'new' star in the constellation of Cassiopeia, which was even visible by day. In fact, he was not the first person to have observed it [6], but because he made detailed studies of it will always be remembered as Tycho's star. He wrote (in De Stella Nova - On the New Star - published in 1573):

It is not surprising that this even stirred the public's imagination; not only scholars but everyone. What could it possibly mean? Some thought it might be a second star of Bethlehem, announcing a second coming of Christ; others speculated about forthcoming calamities. However, the question that astronomers and philosophers were asking was ... was it a new star or was it something like a sub-lunar comet whose 'fiery vapors' had condensed? Since Aristotle had stated that the heavens were pure and changeless, these were real concerns. Although Tycho had no idea of the origin of this star [7], he made careful measurements of its position relative to the Pole Star and the stars of Cassiopeia, he showed there was no detectable parallax [8]. He concluded that it was not

It dimmed gradually over the weeks; by December it was similar to Jupiter, in the following April it was as bright as the Pole star and it finally disappeared in March 1574. Tycho wrote (showing also his belief in astrology):

Originally, Tycho was reluctant to publish his observations, not because of the likely theological arguments, that caused Copernicus to hesitate, but because he was concerned whether a man of his rank should be an author! He was persuaded that would be alright and accordingly his De Stella Nova was published in 1573. He thought it probable that the new star was formed by condensation of the thin celestial matter of the Milky Way and even claimed he could the 'hole' left after it had disappeared from sight. What was more important, however, was that he decided to devote the remainder of his life to astronomy; he was likely motivated by the questions like ... "who could know what great and important events the stars held for mankind." He planned to settle in Europe and set up an institute where he could make careful and regular observations. Initially, he thought of Basel, in Switzerland, because it was different from and much more intellectual than the world of Danish gentry.

It was about this time he married - or at least, set up home with - Christine, who remained with him until his death. She was from a humble background but that didn't seem to concern the often arrogant and tyrannical Tycho as the marriage - or arrangement - worked well; she bore eight children of whom two died young.

Tycho was, by now, becoming well-known and in 1574 he gave public lectures on astronomy at the University of Copenhagen at the direct request of King Frederick; Frederick had assured him that it would not be beneath his dignity and station to give public lectures. Although allegedly on astronomy, the subject matter was mainly, what we would call today, astrology. He was a believer in astrology for he said:

In 1575, he took a tour of Germany, looking for suitable sites for an observatory, and visited Wilhelm IV, the Landgrave [9] of Hesse. Wilhelm, who was a keen, skilled astronomer and had set up an observatory - during his father's reign - using simple quadrants and sextants, under a movable roof in his castle. Tycho left after a week at the sudden death of one of the Landgrave's daughters and he didn't want to impose on his host's grief. Wilhelm knew that Tycho was considering settling in Germany and so he wrote to King Frederick:

On February 11, 1576 Tycho received an order to appear at Court. The King offered funds for a proper observatory, provided Tycho agreed to remain in Denmark. The King suggested the island of Hven, in the Sont, near Copenhagen (close to the modern Swedish town of Malmo) with all its revenues.

Tycho agreed and so became landlord of Hven (or Ven) and could collect and use the rents paid by the local population. He started building Uraniborg - the 'Castle of Heavens' - in August and within a few years it was completed. Uraniborg was, without doubt, the finest observatory in Europe. It was Flemish in appearance and as well as being an observatory is was also a luxurious home (with running water in the bedrooms!). It also had a jail that was used to punish delinquent tenants of Hven. Later, a second observatory, Stjerneborg, was added nearby.

His observatory housed a variety of astronomical instruments including a huge quadrant and sextants all made to his design. They were used for making very accurate measurements of the positions of stars and the planets. Uraniborg had its own workshop and later a printing press. Hven became known over the years as a major center and many important people visited including James VI of Scotland - later James I of England - in 1590 and who, it is said, gave Tycho two large dogs. One character associated with the Court was Jep, a midget, who sat a Tycho's feet during meals. During his time at Hven he became more authoritarian and a hard landlord. However, his position was safe while Frederick II was King of Denmark.

During his time at Hven he catalogued the positions of some 777 stars with exceptional precision for the time - less than about 0.070 - using only the large quadrants and sextants and his naked-eye [10]. It replaced the catalogues of Hipparchus (180-125 BC) and Ptolemy (c. 90-170 AD), being much more accurate [11]. Also, he followed the motion of the Moon and the planets in detail, particularly Mars, which proved later to be of enormous importance to Johannes Kepler. In 1584 he re-measured the obliquity of the ecliptic, i.e., the tilt of the Earth's axis with reference to the plane of the Earth's orbit around the Sun. He sent his assistant Elias Olsen to Frombork, where Copernicus worked, to carry out the measurements. In addition to proving Tycho correct, i.e., that Copernicus had made an error, Olsen returned to Hven with Copernicus' triquetrum [12], where it was given an honored place.

A total of seven comets appeared during Tycho's time at Hven. The first was seen in November 1577 and he carried out a series of measurements. He discovered that there was no parallax and so it could not be close to the Earth. On November 23, 1577 the comet was close to the bright star Epsilon Pegasi and over a period of three hours he checked the position of the comet. From the data he concluded that the comet must be at least six times further away from the Earth than the Moon and so they were celestial as opposed to sub-lunar. Again, this undermined the Aristotelian theory that the heavens, i.e., the space beyond the Moon's orbit, was changeless; Aristotle, in his Meteorological, stated that comets were fiery phenomena in sub-lunar regions, i.e., in the upper atmosphere. Other comets also showed a similar lack of detectable parallax. In 1582-3 Tycho finally abandoned the Ptolemaic system when he thought he found that Mars was closer to the Earth was less than that of the Sun [13]; Ptolemy's theory always had it greater. Tycho then wondered whether Copernicus' theory was correct.

Although he greatly admired Copernicus, Tycho could not accept Copernicanism totally; partly on religious grounds but also on purely scientific grounds. His arguments on the latter were as follows:

  1. The Earth must be much too heavy to move.
  2. The absence of parallaxes of the stars means that under the Copernican system, the distance between the outermost planet (Saturn) and the nearest stars would be incredibly great.
  3. Tycho supposed that from Earth stars had angular diameters of a few minutes of arc; that meant that they had enormous size, perhaps greater than the diameter of the Earth's orbit.

(In fact, we know now that the stars are great distances from Earth; for example, if a baseball represents the size of the orbit of Saturn then the nearest star will be over a mile away. Furthermore, there are stars whose diameters greater than 186,000 miles, the average diameter of the Earth's orbit. But Tycho lived in the 16th century when such figures were unknown.)

So, assuming that both Ptolemy and Copernicus were wrong, Tycho introduced his own system, the so-called Tychonic system, even though it was not entirely new. In his system the Earth was still at rest and round it traveled the Moon and then the Sun, with the planets orbiting the Sun with different radii. Tycho did not believe in the concept of solid, celestial spheres on which the planets moved, and so the fact that the orbits of Mars, Venus and Mercury crossed the Sun's orbit was not a problem for him. He was extremely proud of his system; indeed, later, as we shall see, he implored Kepler to prove him right.

However, late in the 1580's Tycho was beginning to experience other, more personal problems that threatened his career. In 1588, Tycho's strong supporter, King Frederick II, died. His son, Christian, (later Christian IV), was still a boy and the government was administered by Danish noblemen until he succeeded. Because of his previous strong patronage with Frederick II, however, Tycho was resented by a number of the Danish nobles. He still had a friendship with Chancellor Niels Kaas, but when Kaas died, Tycho's position became increasingly more tenuous. Tycho was not at all faultless; he had a hot temper, he was a hard landlord and he neglected certain duties, such as the upkeep of the Kullen lighthouse. With his main support gone he decided to leave Hven and move to Wandsbeck in Germany, taking his entourage and equipment with him. The last recorded observation from Hven was made on March 15, 1596. Tycho also wrote a letter of complaint to King Christian IV. He received a short, angry answer and as far as Tycho was concerned the break with Denmark was complete; he had to look for a new patron.

It was Rudolph II, the Holy Roman Emperor, who made him an offer. After short stays at Wandsbeck, and visits to Dresden and Wittenberg, he moved to Prague, the capital of Bohemia to take up the position as Imperial Mathematician. He was installed at the Benatky Castle. Rudolph II was unsuited to his role; he was incompetent and many promises were made - including money for a new observatory - and broken. Tycho had no political power and Rudolph was very short of money so he often had no salary and the transport his equipment proved difficult. After a short while he left Benatky and returned to Prague in 1599, where with Longomontanus, his assistant, he continued his observations with the instruments he managed to salvage from Hven [14]. In the meantime, he had received a copy of the Mysterium Cosmographicum (The Cosmographic Mystery) by Johannes Kepler, published in 1596. Although he could have hardly agreed with the ideas Kepler had presented, Tycho was impressed with his mathematical abilities and invited him to become his assistant in Prague. There was some conflict between them initially, principally because Kepler was treated as an inferior, but for the remainder of Tycho's life the two worked well together. They planned the compilation of a new set of tables of planetary motion, the Rudolphine Tables, in honor of their patron.

On October 24, 1601 Tycho Brähe died after a brief illness - possibly due to a burst bladder. He was still relatively young, 54 years old, but he had followed an extravagant life-style. He begged Kepler to complete the Rudolphine Tables and to use the data he had accumulated at Hven to prove the validity of the Tychonic system. Kepler promised to try and, indeed, he did finish the Tables but, rather than confirm the Tychonic system, Kepler used Tycho's extraordinarily precise data to demonstrate that the Solar System was not Ptolemaic, Copernican or Tychonic.

It would be difficult to find two brilliant individuals with such different characters and temperament as Brähe and Kepler. Brähe was a nobleman, a highly practical and highly-skilled observer, was impetuous, conceited, self-centered and arrogant; Kepler had a 'questionable' family, a theorist with no practical skills, he was unhappy, frail and modest. They represented the joining of the 'old' and the 'new'. Although Brähe's theories and explanations were rooted in the past, i.e., philosophical, the precision of his observations was revolutionary; Kepler, despite having one foot in the past and the other in the modern world, sought 'fundamental' truths.

FOOTNOTES

[1] In 1559 he started to use 'Tycho' instead of the Danish 'Tyge'.

[2] In fact, there were six children but Tycho's twin brother either died at birth or shortly thereafter.

[3] Initially, Arab astronomers used the star catalogue in Ptolemy's Almagest but they later drew up their own catalogues. In Spain, King Alphonso X (The Wise) of Castile (d. 1284) invited a number of astronomers to Toledo - for some time, the meridian of Toledo was used as the standard - and had them produce the Alphonsine Tables, completed in 1252, under the direction of Isaac ben Said. They contained data for predicting the positions of planets as well as eclipses of the Sun and Moon and there were in use for about three centuries.

[4] Apparently, King Frederick II of Denmark was crossing the bridge leading to Copenhagen Castle when he fell into the water. Jørgen Brähe went to his rescue but caught pneumonia as a result, from which he died.

[5] To be able to read his instruments to high accuracy Tycho devised an interesting scale:

To read the graduations in minutes of arc, he drew six sloping lines, of ten equally spaced dots, between each degree.

[6] It seems that Wolfgang Schuler of Wittenberg saw it on November 6. On the following night it was seen by Paul Hainzel at Augsburg and by Lindauer at Winterthur, Switzerland.

[7] In fact, this 'new' star was what we call today a supernova, which represents the 'death-agony' of a massive star. When extremely massive stars have used up their main reserves of energy, a catastrophic collapse may occur that produces intense heating of the core, with the result that the star literally blows apart. Material is spread into space in what is called a supernova explosion. Over a short period of time the energy dissipated is enormous but later all that is left is a patch of expanding gas and a very small, highly-dense 'stellar wreck' made up of neutrons. Supernova are rare events; we only have information about five events:

Our Sun is not large enough to become a supernova.

[8] Parallax is the apparent movement of an object relative to another when they are viewed from a different position. For example, close your left eye and point at an object on a nearby wall - like a light switch - with the forefinger of your right hand. Now, close your right eye and view the object through your left eye. You will notice that your forefinger has apparently shifted to the right of the object. This apparent movement is parallax. If there is no detectable parallax then the two objects must be great distances from the point of observation. Brähe observed the position of the supernova relative to other stars as the Earth moved.

[9] A Landgrave was a German count with jurisdiction over a territory.

[10] Optical instruments came much later; the telescope, for example, wasn't used in astronomy until around 1609/1610.

[11] Brähe designated the stars in the same way that Ptolemy had done, i.e., by the parts or limbs of the constellations. In 1603 Bayer published an atlas, Uranometria, of Tycho's stars in which he used Greek letters to indicate the individual stars within constellations, with alpha being the brightest (see the illustration of Cassiopeia in the text).

[12] The triquetrum or three-staff was an instrument used principally for determining the angular altitude of stars. See the biography of Copernicus in this series.

[13] It appears that at the time this may have resulted from a mistake by one of Tycho's assistants!

[14] The large quadrant that featured so prominently in his measurements of the new star was lost in storm in 1572. Hven was ceded to Sweden in 1658. Uraniborg and Stjerneborg were never used again and nothing remains of them, except a few markers and a statue of Tycho Brähe.

REFERENCES

I have used material from the following sources (sometimes quoting verbatim):

Books

Patrick Moore Watchers of the Stars (Michael Joseph Ltd., 1974)

A. Pannekoek A History of Astronomy (Dover Publications, Inc., New York, 1989). It is an unaltered republication of the English translation, originally published in 1961 by George Allen & Unwin Ltd., London. The work was first published by Wereld-Bibliotheek in 1951 with the title De Groei van ons Wereldbeeld.