Dec 142018
 

Today is the birthday (1546) of Tyge Ottesen Brahe, known in the English-speaking world as Tycho Brahe, a Danish nobleman, astronomer, and writer known for his accurate and comprehensive astronomical and planetary observations. He was born in the then-Danish (now Swedish) peninsula of Scania. His observations, done only with the naked eye before telescopes were available, were about five times more accurate than the best available observations at the time.

Tycho aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within a arcminute of their real celestial locations, and also claimed to have achieved this level. But, in fact, many of the stellar positions in his star catalogues were less accurate than that. To perform the huge number of multiplications needed to produce much of his astronomical data, Tycho relied heavily on a new technique called prosthaphaeresis, an algorithm for approximating products based on trigonometric identities that predated logarithms.

Although Tycho admired Copernicus and was the first to teach his theory in Denmark, he was unable to reconcile Copernican theory with the basic laws of Aristotelian physics, that he considered to be foundational. He was also critical of the observational data that Copernicus built his theory on, which he correctly considered to have a high margin of error. Instead, Tycho proposed a “geo-heliocentric” system in which the Sun and Moon orbited the Earth, while the other planets orbited the Sun. Tycho’s system had many of the same observational and computational advantages that Copernicus’ system had, and both systems could also accommodate the phases of Venus, although Galileo had yet to discover them. Tycho’s system provided a safe position for astronomers who were dissatisfied with older models but were reluctant to accept heliocentrism and the Earth’s motion. It gained a considerable following after 1616 when Rome declared that the heliocentric model was contrary to both philosophy and Scripture, and could be discussed only as a computational convenience that had no connection to fact. Tycho’s system also offered a major innovation: while both the purely geocentric model and the heliocentric model as set forth by Copernicus relied on the idea of transparent rotating crystalline spheres to carry the planets in their orbits, Tycho eliminated the spheres entirely. Kepler, as well as other Copernican astronomers, tried to persuade Tycho to adopt the heliocentric model of the solar system, but he was not persuaded. According to Tycho, the idea of a rotating and revolving Earth would be “in violation not only of all physical truth but also of the authority of Holy Scripture, which ought to be paramount.”

With respect to physics, Tycho held that the Earth was just too sluggish and heavy to be continuously in motion. According to the accepted Aristotelian physics of the time, the heavens (whose motions and cycles were continuous and unending) were made of “Aether” or “Quintessence.” This substance, not found on Earth, was light, strong, unchanging, and its natural state was circular motion. By contrast, the Earth (where objects seem to have motion only when moved) and things on it were composed of substances that were heavy and whose natural state was rest. Accordingly, Tycho said the Earth was a “lazy” body that was not readily moved. Thus while Tycho acknowledged that the daily rising and setting of the sun and stars could be explained by the Earth’s rotation, as Copernicus had said, he, nonetheless believed that, “such a fast motion could not belong to the earth, a body very heavy and dense and opaque, but rather belongs to the sky itself whose form and subtle and constant matter are better suited to a perpetual motion, however fast.”

With respect to the stars, Tycho also believed that, if the Earth orbited the Sun annually, there should be an observable stellar parallax over any period of six months, during which the angular orientation of a given star would change thanks to Earth’s changing position. (This parallax does exist, but is so small it was not detected until 1838, when Friedrich Bessel discovered a parallax of 0.314 arcseconds of the star 61 Cygni.) The Copernican explanation for this lack of parallax was that the stars were such a great distance from Earth that Earth’s orbit was almost insignificant by comparison. However, Tycho noted that this explanation introduced another problem: Stars as seen by the naked eye appear small, but of some size, with more prominent stars such as Vega appearing larger than lesser stars such as Polaris, which in turn appear larger than many others. Tycho had determined that a typical star measured approximately a minute of arc in size, with more prominent ones being two or three times as large. In writing to Christoph Rothmann, a Copernican astronomer, Tycho used basic geometry to show that, assuming a small parallax that just escaped detection, the distance to the stars in the Copernican system would have to be 700 times greater than the distance from the sun to Saturn. Moreover, the only way the stars could be so distant and still appear the sizes they do in the sky would be if even average stars were gigantic — at least as big as the orbit of the Earth, and of course vastly larger than the sun. And, Tycho said, the more prominent stars would have to be even larger still. And what if the parallax was even smaller than anyone thought, so the stars were yet more distant? Then they would all have to be even larger still. . . which, in fact, they are.

Kepler used Tycho’s records of the motion of Mars to deduce laws of planetary motion, enabling calculation of astronomical tables with unprecedented accuracy (the Rudolphine Tables) and providing powerful support for a heliocentric model of the solar system. Galileo’s 1610 telescopic discovery that Venus shows a full set of phases refuted the pure geocentric Ptolemaic model. After that it seems 17th-century astronomy mostly converted to geo-heliocentric planetary models that could explain these phases just as well as the heliocentric model could, but without the latter’s disadvantage of the failure to detect any annual stellar parallax that Tycho and others regarded as refuting it.

The three main geo-heliocentric models were the Tychonic, the Capellan with just Mercury and Venus orbiting the Sun such as favored by Francis Bacon, for example, and the extended Capellan model of Riccioli with Mars also orbiting the Sun whilst Saturn and Jupiter orbit the fixed Earth. But the Tychonic model was probably the most popular, albeit probably in what was known as ‘the semi-Tychonic’ version with a daily rotating Earth. This model was advocated by Tycho’s ex-assistant and disciple Longomontanus in his 1622 Astronomia Danica that was the intended completion of Tycho’s planetary model with his observational data, and which was regarded as the canonical statement of the complete Tychonic planetary system.

The ardent anti-heliocentric French astronomer Jean-Baptiste Morin devised a Tychonic planetary model with elliptical orbits published in 1650 in a simplified, Tychonic version of the Rudolphine Tables. Some acceptance of the Tychonic system persisted through the 17th century and in places until the early 18th century; it was supported (after a 1633 decree about the Copernican controversy) by “a flood of pro-Tycho literature” of Jesuit origin. Among pro-Tycho Jesuits, Ignace Pardies declared in 1691 that it was still the commonly accepted system, and Francesco Blanchinus reiterated that as late as 1728. Persistence of the Tychonic system, especially in Catholic countries, has been attributed to its satisfaction of a need (relative to Catholic doctrine) for “a safe synthesis of ancient and modern”. After 1670, even many Jesuit writers only thinly disguised their Copernicanism. But in Germany, the Netherlands, and England, the Tychonic system vanished from scientific literature much earlier.

No dish better suits the celebration of Tycho Brahe than spettekaka or spettkaka (spiddekaga in native Scanian) a dessert that originates in the province of Scania (Skåne) where he was born.  The name means “cake on a spit” which, as you will see from the video, exactly describes its production. A mixture consisting mainly of eggs, potato starch flour and sugar is squirted slowly on to a conical spit which is being rotated over an open fire or other heat source. So, a spinning dessert for an advocate of spinning bodies in space. Spettekaka can range in size anywhere from a few inches to several feet in height and over a foot in diameter. The very large cakes are served by sawing cuboids from the cake, leaving as much standing as possible. Spettekaka is frequently served accompanied by dark coffee, vanilla ice cream and port wine.

This video shows how spettekaka is made. Sorry it is in Swedish, but you’ll get the gist:

Jun 142017
 

Today is the traditional date of the founding of Munich, capital of Bavaria, in 1158 by Henry the Lion who built a bridge there across the river Isar. The name of the city is derived from the Old/Middle High German term Munichen, meaning “by the monks” deriving from the fact that monks of the Benedictine order ran a monastery there, and hence the monk depicted on the city’s coat of arms. The date is, in fact, arbitrary based on the fact that this is the earliest date that the city is mentioned in a document, signed in Augsburg. Henry the Lion, Duke of Saxony and Bavaria built a toll bridge over the river Isar as part of the Old Salt Route, a vital trade route for centuries.

The Old Salt Route (Alte Salzstraße) was a medieval trade route in northern Germany, one of an ancient network of salt roads which were used primarily for the transport of salt, but also for other staples. Salt was a very valuable commodity at that time, sometimes known as “white gold.” The vast bulk of the salt transported on the road was produced from brine near Lüneburg, a city in the northern central part of the country and then transported to Lübeck, a major seaport on the Baltic coast.

It is generally assumed that the Old Salt Route was part of a much longer path connecting the northern and southern towns of the region. One of the oldest documents that confirms Lüneburg’s role in refining and transporting salt dates from 956. According to that document, King Otto I the Great granted the St. Michaelis Monastery in Lüneburg the customs revenue from the saltworks. In those days the city’s wealth was based in large part on the salt found in the area. However, the Old Salt Route attained its peak of success between the 12th and the 16th centuries.

The trade route led from Lüneburg northward to Lübeck (also founded by Henry). From that port city, most of the salt was shipped to numerous destinations that also lie on the Baltic Sea, including Falsterbo, with its renowned Scania market (Danish Skånemarkedet) whose herring trade was one of the cornerstones of Hanseatic League. Salt was used for the preservation of herring which was of immense importance in the Middle Ages. The salt trade was a major source of power and wealth for both Lübeck and the Hanseatic League.

Legend has it that the herring fishery off the Scanian coast was so rich, that one could scoop up the fish with one’s hands. After a visit to the region in 1364, the French crusader Philippe de Mezieres wrote:

Two months a year, that is in September and October, the herring travel from one sea to the other through the Sound, by order of God, in such large numbers that it is a great wonder, and so many pass through the sound in these months, that at several places one can cut them with a dagger.

As early as the 12th century the peninsula had become a center for the herring trade; the Scanian name for the town Falsterbo was Falsterbothe, which meant “the booths for fish from Falster.” The 13th-century German chronicler Arnold of Lübeck, author of Chronicon Slavorum, wrote that the Danes had wealth and an abundance of everything thanks to the yearly catches of herring at the Scanian coast.

Salt wa brought from Lüneburg to a crossing of the Elbe river at Artlenburg (near Lauenburg) and from there, via Mölln, to Lübeck. However, for the most part, the historic trade route was composed of unsurfaced, sandy and often muddy roads through heathland, woods and small villages, making the transport of salt an arduous task. In addition, the route was dangerous given that the valuable cargo attracted thieves, bandits and marauders of all stripes. The dangers faced by those making the long trek, combined with the fact that only relatively small quantities of salt could be carried in any single journey, made moving salt via overland routes very expensive.

In 1175 Munich, fast becoming a vital link on the Salt Road, was officially granted city status and was fortified. In 1180, after the trial of Henry the Lion (in absentia for insubordination by a court of bishops and princes), Otto I Wittelsbach became Duke of Bavaria and Munich was handed over to the Bishop of Freising. (Wittelsbach’s heirs, the Wittelsbach dynasty, ruled Bavaria until 1918.) In 1240, Munich was transferred to Otto II Wittelsbach and in 1255, when the Duchy of Bavaria was split in two, Munich became the ducal residence of Upper Bavaria. Duke Louis IV, a native of Munich, was elected German king in 1314 and crowned as Holy Roman Emperor in 1328. He strengthened the city’s position by granting it the salt monopoly, thus assuring it vital income for its growth and prosperity.

No trouble finding a recipe today, of course, although I should talk about salt in the diet in general first. I pretty much always put “salt to taste” in recipes rather than giving precise amounts because tastes vary so dramatically, as well as dietary needs. In certain recipes, notably yeast products and some pastries, a small amount of salt is essential, but for the most part you can do without it if you train your palate. I almost never use salt in recipes but I get more than my recommended daily allowance, which is only about 1 to 2 grams, without trying. The thing is that salt was such an important part of food preservation in antiquity forwards that in general people’s taste buds became habituated to foods with high salt content so that foods with lower salt content tasted bland. Nowadays salt is no longer needed for preservation but the habituation remains. Clinical research results are not entirely definitive, but there seems to be a strong correlation between high salt intake and high blood pressure. In my humble opinion, it’s best not to take risks. For many years I had very low blood pressure, but I stopped using salt in cooking anyway. If you are habituated to high salt content and try to limit it when you develop high blood pressure, you are too late. It takes several months but you can reduce your salt intake slowly – day by day – and you’ll find that over time your taste buds adjust so that low salt or no salt recipes taste fine.

Herring spoils very quickly and so for centuries it had to be preserved by salting or smoking, or both, and these methods are still used because the results are not just practical but produce distinctive tastes as well. Because I don’t commonly cook with salt, heavily salted fish tastes overpowering to me. The usual instructions for cooking salt herring start by telling you to cover the fish in water in a large bowl and refrigerate overnight. I go a few steps further by placing it in a colander which I immerse in a large bowl of cold water, for about 8 hours, changing the water every hour. The colander facilitates lifting the fish out each time. Then I immerse the fish in a bowl of water, cover, and refrigerate overnight.

Herring is a bony fish, so before you cook it you need to fillet it and remove the bones. A pair of tweezers is more or less essential.  Then the salted variety can be prepared in a number of ways. Breading the fillets and frying them  in a little olive oil with garlic is very traditional, but I’m more partial to making it into a classic English fish pie which I have mentioned before.  I make it easier to debone the fish by poaching it lightly first and then scraping the meat (in chunks as much as possible) from the bones. Then I prepare mashed potatoes with leeks and onions, mix it together with the fish, and bake in a hot oven until the top is golden. Proportion of fish to potatoes is entirely up to you.  About 1 part fish to 2 parts potato works for me.