Skip to main content
Physics LibreTexts

3.4: Tycho Brahe

Tycho Brahe took the next step towards confirming Copernicus' hypothesis. Tycho (as he is known) was a colorful character who was perhaps the greatest observer of the pre-telescopic era. His life was marked by swift changes of fortune. Born to a penniless family, he was raised by a foster father who could not have children of his own. His foster father died of pneumonia after saving the King of Denmark from drowning in an accident, and in gratitude the king made Tycho a rich man. Tycho wore a silver nose to cover a dueling mutilation — suffered in an argument over who was a better mathematician! At age 16, he noticed the errors in the planet positions predicted by the old Ptolemaic system. This led to his lifelong interest in recording positions of planets. 

Portrait of Tycho Brahe. Click here for original source URL

Tycho Brahe made observations that challenged key elements of Aristotle's conception of the universe. In 1572, when he was only 25 years old, he observed an exploding star that temporarily brightened and then faded. This exciting observation refuted the ancient belief that the stars were forever unchanging, mounted on their starry crystalline sphere. Five years later he tracked the motion of a bright comet from night to night and compared his data with that of observers in other parts of Europe. The comet always formed the same pattern with respect to the stars as seen by any observer. Tycho was able to show that it was much further away than the Moon and not an atmospheric phenomenon as Aristotle had taught. Moreover, the path of the comet required that it traverse the orbits of several planets, calling into question the whole idea of crystalline spheres. By demonstrating that stars and planets show no angular shift compared to the stars as our position shifts with the rotation of Earth, Tycho proved that stars and planets were many times farther away than the Moon.

Sketches made by Brahe in one of his notebooks, depicting his observations of the Great comet of 1577. Click here for original source URL

With funds from the king of Denmark, Brahe built the first modern European observatory, named Uraniborg or Sky Castle, on an island near Copenhagen. The telescope had not yet been invented, but Tycho made the most accurate set of astronomical observations ever, thanks to his fine experimental technique. He used fittings made of rigid metal rather than wood. He sighted objects with a precise angular scale, using a large rotating device like a giant protractor (you should be clear on the distinction between precision and accuracy). He made multiple independent measurements as a way of improving accuracy. Or he combined independent measurements made by himself and his assistants. He improved on the accuracy of previous star and planetpositions by a factor or three or four — his best measurements were accurate to 1-2 minutes of arc. Tycho toiled for twenty years, making observations on every clear night. This formidable set of data would be crucial in understanding the orbits of the planets.

SN 1572, Tycho's Supernova, the remnant of the supernova explosion that Tycho Brahe noticed in 1572. Click here for original source URL

Then Tycho's luck took a turn for the worse. His royal patron King Frederick died, and the young new king was less inclined to tolerate Tycho's troublesome personality. Tycho became an itinerant astronomer, taking a series of posts around Europe. In 1600, he hired a 30-year old mathematician named Johannes Kepler. Tycho's death was as colorful as his life. One evening, while dining at the house of a nobleman, Tycho drank copiously and suffered a burst bladder. Before he died he named Kepler as his successor. And so the brilliant young mathematician inherited the mass of Tycho’s observations and began analyzing the planetary positions.

A colored print of?Tycho Brahe's?Uraniborg?palace-observatory from his 1598 book. This is his plan of the gardens, with the main building in the center and servants' quarters, a printing studio, and other buildings just inside the outer walls. Note that Tycho's design was influenced by buildings he had seen in Venice, and was also constructed in a highly geometrical form. The castle and its ground were perfectly oriented in the points of the compass. Click here for original source URL.