Births on February 2

Nicolaus Reimers, German astronomer (d. 1600)

Nicolaus Reimers Baer: An Autodidact Astronomer and Imperial Mathematician

Nicolaus Reimers Baer (2 February 1551 – 16 October 1600), also widely known by his Latinized name Reimarus Ursus ("bear"), and occasionally as Nicolaus Reimers Bär or Nicolaus Reymers Baer, was a prominent astronomer and mathematician of the late 16th century. His remarkable journey from humble beginnings to the esteemed position of imperial mathematician to Emperor Rudolf II in Prague highlights his exceptional intellect and perseverance. The title of imperial mathematician signified a highly respected scientific role within the Holy Roman Empire, often involving astronomical observations, calendar reform, and the application of mathematics for various imperial needs.

Early Life and Unconventional Education

Born in Hennstedt, a small village in Schleswig-Holstein, Reimers' early life offered little indication of his future scholarly achievements. He received hardly any formal education in his youth, spending his formative years herding pigs until the age of 18. This challenging background makes his later accomplishments even more extraordinary, showcasing his inherent talent and relentless drive for knowledge. His path diverged significantly when he was discovered by Heinrich Rantzau (1526–1598), a powerful and enlightened statesman, humanist, and patron of arts and sciences in Holstein. Rantzau recognized Reimers' nascent abilities and employed him as a geometer from 1574 to 1584. In this role, Reimers gained practical experience in land surveying, cartography, and applied mathematics. This period of patronage was crucial for his intellectual development, enabling him to self-educate extensively. During this time, he published a Latin Grammar in 1580, demonstrating his mastery of the language essential for scholarly discourse, and his significant work, Geodaesia Ranzoviana, in 1583, a treatise on geodesy dedicated to his patron. It was also through Rantzau's connections that Reimers had an initial, fateful meeting with the renowned Danish astronomer, Tycho Brahe.

Collaborations and Key Astronomical Works

Following his time with Rantzau, Reimers continued to expand his intellectual horizons. From 1585 to 1586, he served as a private tutor in Pomerania. Subsequently, from 1586 to 1587, Reimers spent time at the progressive court of William IV, Landgrave of Hesse-Kassel (1532–1592), in Kassel. William IV was himself an avid astronomer who maintained a well-equipped observatory, making his court a significant center for astronomical research. It was in Kassel that Reimers met the brilliant Swiss clockmaker and instrument builder, Jost Bürgi (1552–1632). Their shared status as largely self-taught, or "autodidact," individuals fostered a unique intellectual bond. A notable collaboration between them involved a crucial astronomical text: given that Bürgi did not understand Latin, the scholarly lingua franca of the time, Reimers undertook the monumental task of translating Nicolaus Copernicus's groundbreaking work, De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres), into German for Bürgi. This translation, known today as the "Grazer Handschrift" because a copy survived in Graz, Austria, is a testament to Reimers' linguistic skill and his commitment to disseminating complex astronomical ideas, making them accessible to a wider audience, including ingenious craftsmen like Bürgi who lacked formal classical education but possessed profound practical and mathematical insights.

The Intense Rivalry with Tycho Brahe

Nicolaus Reimers Baer's career, particularly after his appointment as imperial mathematician to Emperor Rudolf II in Prague, became inextricably linked with, and indeed overshadowed by, his bitter rivalry with Tycho Brahe. This contentious relationship arose primarily from a dispute over the intellectual property of cosmological models and mathematical techniques. Tycho Brahe, who would later succeed Reimers as imperial mathematician, vehemently accused Ursus of plagiarizing two key innovations:

• The Tychonic System: A geoheliocentric model of the Solar System where the Earth remains stationary at the center, the Sun orbits the Earth, and the other planets orbit the Sun. Tycho claimed Reimers attempted to present this system as his own invention.
• Prosthaphaeresis: A mathematical method used to simplify complex multiplication and division operations into simpler additions and subtractions, particularly useful for trigonometric calculations. This technique was a crucial precursor to logarithms and revolutionized astronomical computations in an era without electronic calculators.

On the latter issue, the historical consensus has largely sided with Ursus. Reimers explicitly stated that the technique of prosthaphaeresis was the invention of the German astronomer and mathematician Paul Wittich (c. 1545–1586) and the very same Jost Bürgi with whom Reimers collaborated. This intellectual dispute highlights the fierce competition and nascent concepts of intellectual property within the scientific community of the late Renaissance.

Reimers' Unique Cosmological Model

In 1588, Nicolaus Reimers published his own cosmological model, which he claimed to have devised. This model proposed a Solar System where the planets revolved around the Sun, while the Earth merely spun on its axis. This placed Reimers' model in a unique position, differing from both the traditional geocentric (Earth-centered) Ptolemaic model and Copernicus's heliocentric (Sun-centered) model.

• Difference from Copernicus: While Copernicus postulated that the Earth orbited the Sun as well as rotating on its axis, Reimers' model retained a stationary Earth in terms of its orbital path around the Sun. His Earth only rotated daily.
• Adherence to Aristotelian Principles: A key driver for Reimers' objection to the full Copernican model was its perceived violation of prevailing Aristotelian physics. The Aristotelian principle, deeply ingrained in medieval and early modern thought, posited that a body could only possess one "natural movement." For the Earth, its natural motion was to be stationary at the center of the cosmos. Copernicus's model, with the Earth both rotating on its axis and orbiting the Sun, implied two natural motions for a single body, which was seen as problematic by many contemporaries, including Ursus.

Reimers' geoheliocentric model, sometimes referred to as the "Ursine system," attempted to reconcile the observed planetary motions with the prevailing philosophical and physical objections to a fully heliocentric system, particularly concerning the Earth's motion.

The Keplerian Interlude and Model Discrepancies

The intricate web of astronomical rivalries and theoretical advancements of the era saw Johannes Kepler, then a young and ambitious astronomer, inadvertently caught in the middle. Early in his career, while seeking the patronage of Tycho Brahe, Kepler sent a laudatory letter to Reimers, likely hoping to curry favor. Ursus, however, took advantage of this by publishing the letter in the preface to his own work, Fundamentum Astronomicum (1588), ostensibly to lend credence to his claims of priority for cosmological ideas similar to Tycho's, or at least to highlight Kepler's perceived endorsement. This "faux pas" created a significant breach between Kepler and Tycho, which required considerable effort to mend.

The differences between the various geoheliocentric models were subtle yet profound:

• Tycho's System: The Earth was stationary. The Sun orbited the Earth, and the other planets orbited the Sun. Crucially, Tycho's calculations and observations, as he understood them, implied that the orbits of Mars and the Sun intersected. This intersection led Tycho to a significant conclusion: that there could be no solid celestial spheres, as proposed by earlier astronomers to carry the planets, because such spheres could not interpenetrate.
• Ursus's and Roslin's System: In contrast, the model advocated by Ursus and his follower, Helisaeus Röslin (1545–1616), proposed that the Earth underwent a daily rotation on its axis. Furthermore, their models posited that the Martian and Solar orbits did not intersect, thereby avoiding Tycho's conclusion about the non-existence of solid celestial spheres based on orbital interpenetration. However, Reimers' illustration of his model presented its own set of orbital overlaps, notably showing the orbits of Mercury and Venus intersecting the Martian orbit, and even Jupiter's orbit, which were inconsistencies.

  Kepler's Pivotal Discoveries and Historical Legacy

  The resolution of these orbital discrepancies and the broader debate over cosmological models ultimately came through the meticulous work of Johannes Kepler. After Tycho Brahe's death, Kepler inherited his extensive and remarkably accurate observational data. Kepler discovered that Tycho had concluded that the Martian and Solar orbits intersected because he had mistakenly inferred from his data that Mars, at opposition, was closer to the Earth than the Sun was. The root of this error lay with a research assistant's mistaken calculation of Mars's daily parallax from observations made during its 1582-83 opposition. The assistant had calculated Mars's parallax as greater than the Sun's presumed 3-arcminute parallax.

  However, Kepler's rigorous re-analysis of Tycho's raw observations revealed little or no Martian parallax, which accurately implied that Mars was, in fact, further than the Sun at opposition. This critical correction had profound implications: it directly refuted Tycho's original intersecting-orbit configuration and, paradoxically, lent support to the non-intersecting orbital arrangements found in the models of Ursus and Roslin, at least concerning the Mars-Sun relationship. This revelation could have tipped the scales in favor of Ursus's and Roslin's systems over Tycho's in terms of orbital geometry.

  The historical question of whether the dominant astronomical system of the 17th century was Tycho's geoheliocentric system or that of Ursus and Roslin (especially regarding non-intersecting Solar and Martian orbits and the Earth's rotation) remains a complex subject of scholarly debate. While Tycho's name is often more prominently associated with geoheliocentrism, the nuanced differences and Kepler's later corrections highlight the fluidity of astronomical thought during this transformative period. Ultimately, Reimers' contributions, despite the controversies, were an integral part of the intellectual ferment that paved the way for Kepler's laws of planetary motion and Isaac Newton's universal gravitation.

  Death

  Nicolaus Reimers Baer passed away in Prague on 16 October 1600. His life, marked by self-taught brilliance, groundbreaking contributions, and intense intellectual rivalries, left an undeniable, albeit complex, imprint on the history of astronomy.

  Frequently Asked Questions About Nicolaus Reimers Baer

  Who was Nicolaus Reimers Baer?

  Nicolaus Reimers Baer, also known as Reimarus Ursus, was a German astronomer and mathematician who served as Imperial Mathematician to Emperor Rudolf II in Prague during the late 16th century.

  What was Nicolaus Reimers Baer's background and education?

  Born into humble circumstances in Hennstedt, he received little formal education in his youth, herding pigs until age 18. He was largely self-taught, later employed as a geometer by Heinrich Rantzau, who became his patron.

  What was the "Grazer Handschrift"?

  The "Grazer Handschrift" is a surviving German translation of Nicolaus Copernicus's De Revolutionibus Orbium Coelestium. Reimers translated this pivotal astronomical text for the instrument maker Jost Bürgi, who did not understand Latin.

  Why was Reimers a rival of Tycho Brahe?

  Their rivalry stemmed from disputes over the originality of cosmological models, specifically the geoheliocentric system, and the mathematical technique of prosthaphaeresis, which Tycho accused Ursus of plagiarizing. History has largely sided with Ursus regarding the origin of prosthaphaeresis, crediting Paul Wittich and Jost Bürgi.

  What was unique about Reimers' cosmological model?

  Reimers' model proposed that the planets revolved around the Sun, while the Earth itself only spun on its axis. This differed from Copernicus's model, which also had the Earth orbiting the Sun. Ursus's model aimed to reconcile planetary motions with the Aristotelian principle of a single natural movement for a body.

  How did Johannes Kepler get involved in the Reimers-Tycho rivalry?

  Kepler, early in his career, sent a laudatory letter to Reimers while seeking Tycho's patronage. Reimers controversially published this letter, causing a rift between Kepler and Tycho that had to be later reconciled.

  What was the significance of Kepler's findings regarding Mars's orbit?

  Kepler discovered that Tycho's conclusion of intersecting Martian and Solar orbits was based on a mistaken calculation of Mars's parallax. Kepler's re-analysis showed little or no Martian parallax, implying Mars was further than the Sun at opposition. This correction supported the non-intersecting orbital models, including Ursus's, over Tycho's original assertion.