TYCHO BRAHE 1 – Corsairs & Captives

This week, we’re going to look at something a little different. Instead of focusing on corsairs or captives directly, we’ll be looking at some background—at an issue that affected everybody who ever sailed a ship.

Navigation.

We take navigation for granted these days. Sailors have detailed nautical charts, sophisticated navigational instruments, and GPS. Four centuries ago, however, none of these things existed., and navigating while at sea was a huge challenge—whether you were an ordinary pirate, a European privateer, of a Barbary corsair.

One of the ways to navigate, if you lack sophisticated instruments, is to keep track of the position of the stars. If you have a star chart that accurately depicts the position of the stars in the sky at a given location and time of year, and if you can match you observation of the night sky with that chart… presto! You have your location.

The problem was that, four hundred years ago, no such accurate star chart existed—until one man created it.

That man was Tycho Brahe, a Danish astronomer, who lived from 1546-1601.

This week and next, we’re going to look at Tycho Brahe’s life.

Tycho Brahe was born into the Danish nobility. While still an infant, he was fostered by his paternal uncle, Jørgen Brahe, who was childless (some versions of the story have it that Jørgen Brahe abducted the infant Tycho, so desperate was he to have a son to rear). Growing up a child of privilege as he did, it was natural that, when the time came, Tycho attended university—the University of Copenhagen.

His uncle Jørgen intended that Tycho should study law and eventually take up a career in government. A problem emerged, however. Tycho found something else that fascinated him far more than the law: astronomy. This precipitated a classic parent/child struggle. It is easy to imagine uncle Jørgen lecturing his nephew: “Astronomy may be fine as a hobby, but it’s no fit pursuit for a serious person. You must be practical! A degree in Law will enable you to build a prestigious career and make your family proud.”

The arguments and lectures had limited effect, though, and in an effort to remove his nephew from temptation, uncle Jørgen sent him off to Leipzig University with a hired tutor to chaperone him and make sure he stuck to studying Law. This ploy failed, for in Leipzig, Tycho eluded his tutor’s control and continued his pursuit of Astronomy.

Some little time after Tycho’s returned to Denmark (by now, he was nineteen), his uncle Jørgen Brahe died. This put an end to the pressure for Tycho to study Law. A year later, he was off to the University of Rostock, where he developed a new interest: Alchemy.

While in Rostock, only a couple of weeks after his twentieth birthday, he famously got into a sword duel and had part of his nose sliced off (he wore a metal prosthetic over his nose ever after; you can see it depicted in the illustration of him at the top of this post).

For the next few years, Tycho led a peripatetic existence, coming and going from Denmark and the German states and spending time in places like Basel, Freiburg, and Augsburg, all the while pursuing Astronomy. During this period, he began to develop a reputation as a serious Astronomer. One of the events that cemented that reputation was the appearance of a supernova in 1572—a nova stella, as Tycho called it (Latin for “new star”), a term that eventually morphed into our modern name.

One of the fundamental tenets of Astronomy up until this point (taken from the standard text: Almagest, a treatise written in the second century AD by the Greek astronomer Ptolemy) was that the stars were fixed and eternal—that they were ‘the heavens’ in a literal sense, and therefore perfect and immutable. The sudden appearance of a brand-new star apparently out of nowhere upended this.

The standard response at the time was to dismiss this new ‘star’ as a mere sub-lunar phenomenon, that is, as an event taking place below the level of the moon and so below the level of the perfect and immutable ‘heavens’—thus averting the threat to the perfection of the Ptolemaic system. Tycho, however, did not buy this dismissal. Through a series of observations, he demonstrated that this new star showed no evidence of parallax.

Parallax is the apparent displacement of an object against its background when measured from different points of observation. For example, if you observe Mars simultaneously from Copenhagen and Bologna, it will appear, as seen from each position, to be in a slightly different position relative to the stars behind it. When observing stars, the difference in position of two cities is actually too small to be significant, and one must rely on the shift in position that happens as the Earth orbits the Sun (the relative position from which one views, say, the North Star in December is different from that of July).

After closely observing the new star of 1572 for months, Tycho determined that it showed no parallax—no shift in position relative to the stars behind it—and so he argued that it must be a new fixed star among the other fixed stars. This was a revolutionary claim, but one that was backed up by meticulous—and indisputable—observation records. The use of such careful, continuous observation was to characterize Tycho’s career for the rest of his life.

By the time he finally returned to Denmark to settle in the early 1570s, Tycho had a reputation as a renowned astronomer—though he was still not yet thirty years old. On the basis of that reputation, the Danish King, Frederick II, granted him the island of Hven on which to build an observatory, along with an annual stipend of 500 rigsdalers—serious money in those days (the average annual wage for an ordinary farm hand or day laborer in that time would have been about 40 rigsdalers). Brahe was paid extra to take on students and instruct them in mathematics, the theory of navigation, and astronomy.

Tycho Brahe received such generous treatment because the times were changing.

The change is sometimes referred to as the ‘scientific revolution.’ It was intimately bound up with Humanism, the (then) new sense of the primacy of human thought and experience over the traditional Scholastic approach that prioritized knowledge contained in a canon of approved texts. This humanist/scientific revolution was an epistemological shift—a change in how people came to know about the world. Rather than focus on interpreting the knowledge expounded in the old texts, the practitioners of this new approach focused on interrogating the world. This meant making observations, doing experiments, and then moving on from there to devise possible explanations (hypotheses) that accounted for what they had observed. This is the ‘scientific method’—a profoundly different approach from the scholastic form of book knowledge that dominated the Middle Ages.

Tycho Brahe played an important role in all this.

For further details about Tycho Brahe and the observatory he built on the island of Hven, see the next post here in this blog.