Science & Scientists in Berlin. A Guidebook to Historical Sites in the City and Surroundings

By Brigitta von Rekowski and Andrew Fletcher

Science & Scientists in Berlin is a richly illustrated guidebook providing informative biographies of 22 major scientists and 11 mathematicians linked to the metropolis, from polymath Gottfried W. Leibniz (b. 1646) to computer inventor Konrad Zuse (d. 1995). As well as renowned figures like Albert Einstein, the book includes scientists who deserve to be better known, such as flight pioneer Otto Lilienthal. Their world-changing achievements are described in a lively and accessible style.
 
Follow in the footsteps of the protagonists using the comprehensive gazetteer and 18 colour maps which guide you to almost 200 sites associated with their lives: such as plaques, monuments, laboratories, museums, residences & graves.
 
Anyone who is interested in both science and Berlin’s history, and who wants to learn about the people who created this unique past and experience the places where it comes alive, needs a guidebook like this…

• Language: English
• Publisher: Troubador Publishing Ltd
• Release date: Apr 28, 2023
• ISBN: 9781803137933

Brigitta von Rekowski

A Berliner, Brigitta von Rekowski is a mathematician with a PhD in astrophysics. Following academic research in Berlin, Potsdam and Great Britain, she has researched Berlin’s science history and the work of its protagonists.

Book preview

PREFACE

Are you interested in science? Will you be visiting or do you live in Berlin? If so, this book is for you! There are plenty of guidebooks available for someone who is interested in the political and military history, arts, and culture of the city, but until now, there have been none that focus on the science and scientists of Berlin. This guidebook brings to life the unique scientific past of the metropolis over the last three centuries, featuring pioneering people and their stories, and it guides you to memorable places associated with this fascinating aspect of Berlin’s history.

About a decade ago, we started to seek out science-related sites during our regular visits to the city. Adding a theme to a sightseeing programme takes one to locations one would otherwise miss out on; it is a motivation to get out and explore beyond the usual tourist trail. In our case, it brought to our attention important and interesting disciplines, people and places we did not know very much about. We both have PhDs, Brigitta in astrophysics and Andrew in applied mathematics, and we have worked as academic researchers, but Andrew (a non-Berliner, unlike Brigitta) had never heard of Otto Lilienthal or Konrad Zuse.

Berlin has long been one of the major centres of the scientific world. Here, Einstein completed and presented his revolutionary theory of general relativity, Otto Hahn first split the atomic nucleus, and Robert Koch discovered the causes of tuberculosis and cholera and also laid down the basic rules for the control of epidemics. Other pioneers include Otto Lilienthal, who laid the scientific groundwork for aviation with his experimental hang-glider flights (which were the world’s first and cost him his life), and Konrad Zuse, who built the first freely programmable computer.

In this book, you will find richly illustrated chapters on 22 major scientists from the 17th to the 20th centuries, from Leibniz and Euler to Wernher von Braun, and an additional chapter covering 11 mathematicians. Each chapter describes the person’s life and scientific work. Uniquely, we provide an informative gazetteer of almost 200 associated sites – such as plaques, monuments, laboratories, museums, residences and graves – whose locations are given on a set of maps. Some of the places illuminate the more personal side of the scientist: the house where Lise Meitner spent her last night in the city before having to flee for her life, Einstein’s allotment, and the garden where Max Planck played tag with his children. We have included sites in the surroundings of the city, Potsdam and the Land Brandenburg, as they are too good to miss, and in any case, one of the attractions of Berlin is the ease with which one can get out into the surrounding towns and countryside.

We hope you enjoy tracking down the science history of this city and get a good understanding of the lives and work of the people involved!

Brigitta von Rekowski & Andrew Fletcher, 2022

CHAPTER 1

GOTTFRIED W. LEIBNIZ (1646–1716), POLYMATH

LEIBNIZ’S BIOGRAPHY

Gottfried Wilhelm (von) Leibniz was born in Leipzig, Germany, on 1 July 1646. He is often reckoned to be the last polymath; he was a notable mathematician, philosopher, logician and physicist. For four decades, he was in the service of the House of Welf in Hannover, working for 30 years on a compilation of the history of the Guelf dynasty, which he left unfinished. Leibniz may have been ennobled to the status of a Freiherr von (baron) towards the end of his life, but there is no clear historical record of this. The Leibniz-Butterkeks shortbread biscuit was created in the late 19th century by a Hanoverian merchant, who named it so in honour of his prominent fellow citizen.

Leibniz entered the University of Leipzig at the age of 15. He studied law (jurisprudence), philosophy, mathematics and logic, as well as some Latin and Greek poetry. In 1667, he gained a doctorate in canon and civil law from the University of Altdorf near Nürnberg. Although the university then offered Leibniz a position, he did not embark on an academic career but got involved with an alchemy group associated with the Rosicrucians in Nürnberg. Following contacts he made in Nürnberg, he became a juridical councillor in the service of the elector and archbishop of Mainz in 1670, and he worked on a reformed Civil Code.

Gottfried W. Leibniz.

In 1672, Leibniz went on a diplomatic mission to Paris. He liaised with the Paris Academy of Sciences (founded in 1666) and established many long-lasting contacts with leading scientists. Guided by the Dutch astronomer, mathematician and physicist Christiaan Huygens (1629–1695) (the discoverer of the correct shape of Saturn’s rings), he began intensive mathematical studies.

From Paris, Leibniz went on a diplomatic mission to London in 1673. While in London, he presented a prototype of his mechanical calculating machine to the Royal Society of London for Improving Natural Knowledge (the Royal Society) (founded in 1660). It was the first machine equipped to perform all four basic arithmetic operations: addition, subtraction, multiplication and division. A few months later, Leibniz would be elected a fellow of the Royal Society, and during the following years, he would develop the binary number system and design a calculating machine based on it (in lieu of the decimal number system). The technical realisation of such a machine was not made until 1938, though, when the world’s first freely programmable calculating machine was completed: a mechanical construction invented and manufactured by the German engineer Konrad Zuse (1910–1995) (see Chapter 21: Konrad Zuse). Leibniz’s diplomatic missions in London and Paris ended in 1673 when he learned that the elector-archbishop of Mainz had just died. He did not return to Mainz, however, but stayed in Paris for the next three years.

In Paris, between 1673 and 1675, Gottfried Leibniz developed the infinitesimal calculus, both differential and integral, independently of the English physicist, mathematician and astronomer Sir Isaac Newton (1643–1727), who had developed his form of calculus during the Great Plague of London from 1665–1666, but who had not published the work. In fact, Leibniz would publish several years before Newton – his differential calculus in 1684 and his integral calculus in 1686 – both in the scientific journal Acta Eruditorum (founded in Leipzig in 1682), while nothing would be formally published on Newton’s calculus until 1693. Newton’s main work on calculus – the Method of Fluxions, as Newton called it – was published posthumously, in 1736, although Newton had completed it back in 1671. As Leibniz’s calculus spread quickly (see section The spread of Leibniz’s calculus), these circumstances caused Newton to accuse Leibniz of plagiarism around the turn to the 18th century, which led to their priority dispute (known as the Great Sulk) that outlasted Leibniz’s life. Leibniz’s notation for differentiation and integration is still in use. Leibniz also introduced the concept of indices and the terms function and coordinate to mathematics.

As the Paris Academy was not interested in appointing him to a position or making him a member, Leibniz went back to Germany in 1676 where he was employed by the duke of Braunschweig-Lüneburg as a librarian and court councillor. On his journey back, via London, he visited the Dutch philosopher Baruch Spinoza (1632–1677) in Holland, to discuss the latter’s principal work, Ethics.

Gottfried Leibniz remained in the service of the House of Welf in Hannover until his death 40 years later. Furthermore, he also continued improving his calculating machines, immersing himself in philosophical and mathematical studies, and corresponding in Latin, French and German with over 1,000 scholars as well as secular and ecclesiastic sovereigns from Europe and beyond. He was also much-travelled, and at the time, this travel was by horse-drawn coach. He journeyed to the Harz mountains numerous times for a technical project on water drainage from the local mines. For his research on the history of the Guelfs, as commissioned by the new duke in 1685, he went on an extended trip through Germany, Austria and Italy to Naples, which lasted from 1687 until 1690. During the voyage, he – like in Paris in 1672 – seized the opportunity to meet with scholars of various subjects. He declined the offer to oversee the Vatican library, as he did not want to convert to Catholicism. In 1689, Leibniz was elected a member of the Academy of Sciences in Rome (founded in 1603), and in 1699, he was elected a member of the Paris Academy.

On 11 July 1700, Elector Frederick III of Brandenburg – prompted by Leibniz – founded the Kurfürstlich-Brandenburgische Societät der Wissenschaften (Electoral-Brandenburgian Society of Sciences) in Berlin. Upon Frederick’s coronation as King Frederick I in Prussia (not "of Prussia") in 1701, the society was renamed the Königlich-Preußische Sozietät der Wissenschaften (Royal-Prussian Society of Sciences). As a predecessor of today’s Berlin-Brandenburgische Akademie der Wissenschaften (Berlin-Brandenburg Academy of Sciences and Humanities), the society was modelled on Leibniz’s ideas, combining the natural sciences and humanities, and Leibniz was elected its first president. The society’s astronomical observatory, which was built in central Berlin, was inaugurated in 1711. From the late 1690s until 1711, Leibniz frequently travelled to Berlin.

From 1711, Leibniz took part in the planning of the St Petersburg Academy of Sciences (founded in 1724) alongside Tsar Peter I (the Great) of Russia. During his stay in Vienna as a political advisor from 1712 until 1714, Leibniz presented to the Holy Roman Emperor Charles VI a plan for an Academy of Sciences in Vienna; it was eventually founded in 1847.

Gottfried Wilhelm (Freiherr von) Leibniz died on 14 November 1716 at his home in Hannover, Germany. A month later, he was buried in the Neustädter Kirche, the church for the Lutheran members of the court at the time. Since 1993, Leibniz’s remains have been interred in a sandstone sarcophagus that is placed in front of an upright slab bearing the words "OSSA LEIBNITII". The legacy of Leibniz includes more than 15,000 letters.

Sir Isaac Newton is buried in Westminster Abbey in central London.

THE SPREAD OF LEIBNIZ’S CALCULUS

Gottfried W. Leibniz found supporters of his infinitesimal analysis in the two Bernoulli brothers Jakob I (1655–1705) and Johann I (1667–1748) – progenitors of the famous family of remarkable Swiss mathematicians (see Chapter 2: Leonhard Euler and Chapter 3: Johann III Bernoulli). The brothers took up correspondence with Leibniz in 1687, wanting to clarify aspects of the calculus the latter had just published. By the time Leibniz replied, upon his return from Italy in 1690, the Bernoullis had already understood the work. From then on, both parties stayed in close touch with each other.

The Bernoulli brothers played an important role in the further development of Leibniz’s calculus and its application to problems in a diverse range of fields. They originated the calculus of variations, which was a generalisation of infinitesimal calculus in some ways. Crucially, they also transmitted their knowledge to others, which led to the spread of Leibniz’s calculus throughout continental Europe. One of Johann I’s students, the French mathematician Guillaume François Antoine Marquis de l’Hôpital (1661–1704), compiled the first textbook on Leibniz’s calculus, published in 1696 (Analyse des infiniment petits, Pour l’intelligence des lignes courbes). In 1701, both Bernoullis became members of the Royal-Prussian Society of Sciences that was located in Berlin.

Beim Erwachen hatte ich schon so viele Einfälle, daß der Tag nicht ausreichte, um sie niederzuschreiben.

(On awakening I already had so many ideas that the day was not long enough to write them down.)

– G.W. Leibniz

Ohne GOTT [=1] ist NICHTS [=0].

(Without GOD [1], NOTHING [0] is.)

– G.W. Leibniz

Numero deus impare gaudet.

("Gott erfreut sich der ungeraden Zahl. / God rejoices in the odd number.")

– G.W. Leibniz quoting the Roman poet Vergil while commenting on his series expansion of π/4, which only involves odd numbers

The Leibnizstraße in Berlin-Charlottenburg was named after Gottfried Wilhelm Leibniz in 1869 (Map 6:12 and 6:13).

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From the Kurfürstlich-Brandenburgische Societät der Wissenschaften (Electoral-Brandenburgian Society of Sciences) in Berlin to the Berlin-Brandenburgische Akademie der Wissenschaften (Berlin-Brandenburg Academy of Sciences and Humanities); information boards, quotation plaque, bust and picture

> Jägerstraße 22/23, Mitte (Map 2:14)

On 11 July 1700, Gottfried Wilhelm Leibniz founded the Electoral-Brandenburgian Society of Sciences in Berlin, under the patronage of Elector Frederick III of Brandenburg. On 12 July 1700, he was elected the society’s first president. Over the centuries, the society underwent a number of renamings and reorganisations, as follows:

•Königlich-Preußische Sozietät der Wissenschaften (Royal-Prussian Society of Sciences) – it was so named in 1701 when the elector got himself crowned King Frederick I in Prussia

•Académie Royale des Sciences et Belles-Lettres de Prusse (Royal Academy of Sciences and Literature of Prussia) – this renaming occurred around 1745, under King Frederick II (the Great) in Prussia, upon its reform with the help of Euler (see Chapter 2 : Leonhard Euler )

•Königlich-Preußische Akademie der Wissenschaften zu Berlin (Royal-Prussian Academy of Sciences at Berlin) – this is the name given in 1812, upon its reform by the Humboldt brothers (see Chapter 4 : Alexander von Humboldt )

•Preußische Akademie der Wissenschaften (Prussian Academy of Sciences) – this renaming happened in 1918 when the monarchy ended

•Deutsche Akademie der Wissenschaften zu Berlin (German Academy of Sciences at Berlin) – this change was in 1946, on what would have been Leibniz’s 300 th birthday, under the Soviet Occupation of East Berlin

•Akademie der Wissenschaften der DDR [Deutsche Demokratische Republik] (Academy of Sciences of the GDR [German Democratic Republic]) – this name was given in 1972

In 1987, a parallel academy emerged in West Berlin: the Akademie der Wissenschaften zu Berlin (Academy of Sciences at Berlin). In 1992, on the German reunification, the original (Prussian) academy was reconstituted as the Berlin-Brandenburg Academy of Sciences and Humanities.

Until 1752, the society/academy was housed at its astronomical observatory near Unter den Linden (see 2). From 1752 until 1903, it resided at Unter den Linden 8, and from 1914 until World War II (WWII), it was in the current building at the same address. In 1949, the academy relocated to Jägerstraße. Boards outside provide information on the history of the academy in both German and English.

A Leibniz quotation. The text is displayed in both: block letters and the hand-writing of Leibniz (between the lines of print).

Inside the academy building, Leibniz is commemorated in multiple ways. In the foyer, a plaque displays Leibniz’s words from 1700:

Man müsste gleich anfangs das Werk samt der Wissenschaft auf den Nutzen richten

(Right from the start one should focus work and science on their usefulness)

On the third floor, a Leibniz bust, created in bronze by Janulis Tembridis in 1990, can be found in the corridor leading to the president’s office.

Also in the academy’s headquarters here at the Gendarmenmarkt is a portrait of Leibniz, which is surrounded by pictures of other notable academy scholars (see Chapter 2: Leonhard Euler).

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From the Berliner Sternwarte (Berlin Observatory) to the Sternwarte Babelsberg (Babelsberg Observatory); Humboldt bust

> An der Sternwarte 16, Babelsberg (Map 12:1)

The Berliner Sternwarte (Berlin Observatory) was founded, together with the Electoral-Brandenburgian Society of Sciences in Berlin, on 11 July 1700 (see 1); the astronomical observatory belonged to the society. A few months earlier, the Protestant states of the Holy Roman Empire had finally followed the Catholic states in abandoning the Julian Calendar in favour of adopting the more accurate Gregorian Calendar, and the patent for the production of the new calendar had been given to the planned observatory on 10 May 1700. The income generated from making and selling the calendars would be used to support the society financially; this was Leibniz’s idea.

The 27-metre-high observatory tower, erected near Unter den Linden in Berlin-Dorotheenstadt, was inaugurated in 1711; the society/academy was based there until 1752. From 1767–1787, Johann III Bernoulli (1744–1807) – grandson of Johann I – held the directorship of the old observatory (see Chapter 3: Johann III Bernoulli).

From 1832–1835, the new observatory was built near the Besselpark (Bessel Park) in Berlin-Friedrichstadt, then on the periphery of Berlin; the old tower was ultimately demolished in 1903. The new facilities, including better observational instruments, had been made possible thanks to the support of Alexander von Humboldt (see Chapter 4: Alexander von Humboldt). From May to August 1835, the German astronomer and mathematician Friedrich Wilhelm Bessel (1784–1846) carried out observations with his own pendulum clock in a magnetic lodge on the grounds of the observatory; these observations served to establish a new Prussian measurement of length. In 1846, the planet Neptune was discovered from the Berlin Observatory by Johann Gottfried Galle (1812–1910); he found it within 1 degree of the position predicted by the French astronomer, chemist and mathematician Urbain Le Verrier (1811–1877), and did so within one hour of looking for it (see Chapter 4: Alexander von Humboldt).

In 1913, the observatory moved to Potsdam-Babelsberg, to take advantage of better observing conditions, and was renamed the Sternwarte zu Berlin-Babelsberg (Berlin-Babelsberg Observatory). Since 1946 it has been called the Sternwarte Babelsberg (Babelsberg Observatory).

The Sternwarte Babelsberg (Babelsberg Observatory) has belonged to the Astrophysical Institute Potsdam (AIP) / Leibniz Institute for Astrophysics Potsdam since 1992.

In 1992, the Astrophysikalisches Institut Potsdam (AIP) (Astrophysical Institute Potsdam) was founded, and the Babelsberg Observatory became the main institution affiliated with the AIP (see Chapter 15: Karl Schwarzschild). In 2011, the name of the institute changed to the Leibniz-Institut für Astrophysik Potsdam (Leibniz Institute for Astrophysics Potsdam).

Opposite the entrance to the main building is a bust by H. Drake in remembrance of Alexander von Humboldt as a patron of the observatory (see Chapter 4: Alexander von Humboldt). The bust was placed there in 1999.

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Rotes Rathaus (Red Town Hall); frieze with Leibniz scene

> Rathausstraße 15, Mitte (Map 2:20)

The town hall is open to the public on Monday to Friday, 9am–6pm.

A terracotta frieze around the façade of the Rotes Rathaus (Red Town Hall) depicts 36 scenes from Berlin’s history (see Chapter 4: Alexander von Humboldt). One of the scenes represents the foundation of the Electoral-Brandenburgian Society of Sciences in Berlin in 1700; it shows Elector Frederick III of Brandenburg and also Leibniz holding the deed of foundation.

The landmark building, which dates from the 1860s, served as the seat of Berlin’s magistrate. It is made out of red clinker bricks – hence the popular name; its official name is the Berliner Rathaus (Town Hall of Berlin). The frieze was created in the 1870s. Reconstructed in the 1950s, the town hall was the seat of the magistrate and mayor of East Berlin. Since 1991, it has been the seat of the governing mayor and the senate of reunified Berlin. The Goldenes Buch (Golden Book) – the official visitors’ book of the city of Berlin – is displayed in a showcase in the foyer. The Column Hall, with its 9-metre-high ceiling, formerly housing the council’s library, is now used for exhibitions and events.

The frieze at the Rotes Rathaus (Red Town Hall) depicting the Leibniz scene: in the centre is (presumably) Electress Sophie Charlotte (the wife of Elector Frederick III); to the left is Gottfried W. Leibniz; and to the right is Elector Frederick III.

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Humboldt-Universität zu Berlin (Humboldt University [at Berlin]); stained-glass window with Leibniz and Newton

> Unter den Linden 6, Mitte (Map 2:6)

On the first floor by the staircase leading to the Audimax (main lecture hall) in the main building of Humboldt-Universität zu Berlin (Humboldt University [at Berlin]), there are three multi-panelled, stained-glass windows that are the work of Walter Womacka from 1962–1963, entitled Die Wissenschaft erobern (To Master Science). The right window includes portraits of Leibniz and Newton side by side on a red panel.

Humboldt University was established in 1810, more than 100 years after the foundation of the Berlin society/academy and almost a century after Leibniz’s death. As with Leibniz and the academy, Wilhelm von Humboldt (see Chapter 4: Alexander von Humboldt) and his university co-founders included both the natural sciences and humanities. They also combined research and teaching. Among the first famous scholars to teach at the university was the philosopher Georg Wilhelm Friedrich Hegel (1770–1831), who held its philosophy chair between 1818 and 1831.

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Leibniz and Sophie Charlotte at the Schloss Charlottenburg (Charlottenburg Palace)

> Spandauer Damm 10–22, Charlottenburg (Map 6:1)

The palace is open to the public on Tuesday to Sunday, 10am–5.30pm (April to October) / 10am–4.30pm (November to March).

Gottfried Wilhelm Leibniz cultivated a close, mutual friendship with the wife of Elector Frederick III of Brandenburg (1657–1713) (King Frederick I in Prussia from 1701), Sophie Charlotte (1668–1705).

As Sophie Charlotte was interested in philosophy, she frequently invited Leibniz to her palace, where he often stayed for weeks at a time. While they strolled in the palace grounds, he explained philosophy to her and her court ladies. For example, he illustrated the principle of individuation to them by showing them that no two leaves are identical.

Elector Frederick III had arranged for the palace to be built for his wife because she desired a dwelling in close proximity to nature and near Berlin. At the time, the palace was situated near the village of Lietzow in the environs of Berlin. It was completed in 1699 and named the Schloss Lietzenburg (Lietzenburg Palace). Frederick himself, since he was the elector, resided in the Berliner Schloss (Berlin Palace). When he crowned himself king, he had the Lietzenburg Palace transformed into a royal residence. After Sophie Charlotte’s death in 1705, the palace was renamed the Schloss Charlottenburg (Charlottenburg Palace); it was substantially extended under Frederick the Great in the 1740s, heavily damaged in WWII, and reconstructed in the 1950s. The small settlement around the Schloßstraße formed the town of Charlottenburg, of which Lietzow became a part in 1719. Today, Charlottenburg is a part of Berlin.

Schloss Charlottenburg (Charlottenburg Palace).

CHAPTER 2

LEONHARD EULER (1707–1783), MATHEMATICIAN

EULER’S BIOGRAPHY

Leonhard Euler was born in Basel, Switzerland, on 15 April 1707. He was the most outstanding mathematician of the 18th century, not least because of the many symbols and terms he introduced or standardised in scientific notation that we still use today: e (Euler’s number), i, π, f(x), Σ, Δy, sin, cos, tan, cot and many more.

Euler’s mathematical education began through his father, who was well acquainted with those distinguished mathematicians the Bernoulli brothers; Euler’s father attended lectures by Jakob I Bernoulli, together with the latter’s younger brother Johann I Bernoulli, and he also knew the Bernoullis socially. This not only inspired Euler to study but also put him in contact with the Bernoullis. Johann I taught him mathematics privately, encouraged his talented pupil and was available for mathematics questions every Saturday afternoon. Before the age of 20, Euler finished his university studies in philosophy and mathematics, and he was then offered a position at the St Petersburg Academy of Sciences. This appointment to the academy had been facilitated by his good friend Daniel I Bernoulli (1700–1782), son of Johann I, who had been called to the academy as a mathematics professor two years earlier. The St Petersburg academy had just been founded, inspired by Leibniz and on the initiative of Tsar Peter I (the Great) of Russia, and it was looking for suitable foreign members. Euler arrived in St Petersburg in the spring of 1727.

Leonhard Euler.

In St Petersburg, Euler was initially an assistant in the medical section of the academy. A few years later, he became a professor of physics (aka natural philosophy) and a member of the academy, and in 1733, he obtained the senior chair as professor of mathematics, succeeding Daniel I, who had gone back to Basel. This post made Euler the chief mathematician at the academy, and during the following decade, he was very productive scientifically. The publication of his book Mechanica in 1736, which was the first book to treat Newton’s method of fluxions using techniques from mathematical analysis, helped him to establish himself as a leading mathematician. During that time, Euler was also involved in Russian map-making.

In 1741, one year after ascending to the throne, Frederick II (the Great), king in Prussia (from 1772 onwards, king of Prussia), called Euler to Berlin. He wanted to reform the Königlich-Preußische Sozietät der Wissenschaften (Royal-Prussian Society of Sciences) with Euler’s help, to meet the standards set out by Gottfried Leibniz at the society’s foundation in 1700 (see 3 and Chapter 1: Gottfried W. Leibniz). Euler arrived in Berlin with his wife and children in the summer of 1741.

Delayed by the Silesian Wars, the society was eventually transformed into the Académie Royale des Sciences et Belles-Lettres de Prusse (Royal Academy of Sciences and Literature of Prussia) in around 1745. The French mathematician, astronomer and philosopher Pierre-Louis Moreau de Maupertuis (1698–1759) – who in 1737 was called the flattener of the Earth when he showed that the Earth was flattened at the poles according to the theory of Newton – became the academy’s president, and Euler became the director of its Mathematical Class. Voltaire had made a recommendation to the king that he appoint Maupertuis as president, and the French mathematician, physicist and philosopher – and future Voltaire friend – Jean-Baptiste le Rond d’Alembert (1717–1783) had endorsed Euler as the greatest mathematician.

With his new role, Euler was busy at Frederick the Great’s court for the next 20 years. The academy wanted to become a leading centre of science in Europe, and a number of other assignments were to come to Euler. Leonhard Euler acted as academy organiser, supervised the academy’s observatory, tended to the academy’s publications, and was also entrusted by the king with a variety of practical tasks, such as works for the king’s botanical gardens, the levelling of the Finowkanal (Finow Canal) linking the Oder and Havel rivers (see 5), the drainage of the Oderbruch marshland, dam and bridge construction in East Friesland, and financial calculations in the service of Prussia. During the Seven Years’ War (1756–1763), Euler also acted as the translator for the Prussian state, thanks to his excellent knowledge of the Russian language. In 1749, Frederick the Great asked Euler to make calculations for the hydraulic system of the eagerly anticipated Große Fontäne (Great Fountain) in the park of his summer residence Sanssouci in Potsdam (see 4).

The water reservoir for the Große Fontäne (Great Fountain) in Sanssouci (see 4).

Despite all this work for the king and academy, Euler was also extremely productive in his own scientific research. During his 25 years in Berlin, he published hundreds of scientific articles, wrote several textbooks, gave lectures, and also published popular scientific and philosophical works. In 234 letters – which were composed from 1760–1762, addressed to a juvenile Prussian aristocrat and published as Lettres à une princesse d’Allemagne […] from 1768–1772 – Euler wrote in the French language on various topics of physics and philosophy in an accessible, non-technical style. Those letters revealed his profound religious faith.

Euler hat in seiner Berliner Zeit die gesamte Mathematik umgestaltet.

(During his time in Berlin Euler has transformed all mathematics.)

– C. G. J. Jacobi (1804–1851)

Over time, Euler’s relationship with the king deteriorated, and he therefore left Berlin in 1766 to return to St Petersburg. Euler’s departure was largely caused by Frederick the Great’s distrust of things he did not comprehend, most of all mathematics. Although the king did acknowledge some usefulness in the mathematical sciences, he was not interested in Euler’s mathematical work. For example, he did not listen to Euler’s expertise regarding the Sanssouci fountain; the king and his engineers ignored Euler’s advice on the design of the pipework, and this – along with Frederick the Great’s stinginess – resulted in the fountain project being a fiasco during the king’s lifetime.

Furthermore, Frederick the Great’s Francophilia demanded that his academy president have French elegance and spirit and be glamorous and scintillating. But the sociable, cheerful and uncomplicated – yet modest, critical and orthodox – Euler could not offer him this. Thus, the flute playing, philosophising king did not offer Euler the academy’s presidency; in particular, not after Maupertuis’s death in 1759, as in his eyes, Euler was not sufficiently aesthetic. Euler resented this, as he had often covered for Maupertuis in the latter’s function as academy president.

When Euler finally requested his release from the academy in 1766, however, Frederick the Great told him to withdraw his resignation. But Euler had made up his mind, and eventually, the intervention of Tsarina Catherine II (the Great) of Russia moved the king to let him go. Once back at the St Petersburg Academy of Sciences, with which he had remained in close contact during his time in Berlin, Euler was received honourably.

In that same year of 1766, the Italian-French mathematician and astronomer Joseph-Louis Lagrange (1736–1813) (who was made a count by Napoleon in 1808) became Euler’s successor as the mathematical director of the Royal Academy of Sciences and Literature of Prussia, on the recommendation of d’Alembert. Lagrange had corresponded with Euler in the mid-1750s and respected him greatly, and therefore he accepted the position in Berlin only when Euler had left the city. Lagrange would stay in Berlin until 1787 (the year after the king’s death in 1786), which was almost as long as Euler, working in analytical and celestial mechanics, number theory, and algebraic and differential equations. Those 21 years in Berlin were very fruitful for Lagrange’s scientific work: here, his Mécanique Analytique came into being.

In 1771, Euler’s house in St Petersburg was destroyed by fire, but he rescued his mathematical manuscripts. Around that time, he went completely blind; he had already lost sight in his right eye after an illness during his first stay in St Petersburg, taking the loss with humour. Euler stayed in St Petersburg for the rest of his life, continuing to work right until his death. Thanks to his phenomenal memory (he could recite Vergil’s Aeneid by heart) and his aptitude for mental calculations, he could carry on with his research despite his blindness, writing down his results with chalk on big slates, and receiving assistance from his sons and academy members. His extraordinary ability to concentrate helped too, and almost half of his scientific work was done after his return to St Petersburg, where he was much valued. Euler was so productive that the academy needed nearly five decades to publish his legacy posthumously.

Euler said that some of his best ideas came when he had a baby on his arm and children playing around his feet. He had married Katharina Gsell in 1734 (she was one day younger than him) and had 13 children with her, of whom five had reached adulthood and three would outlive him. In 1776, three years after his wife’s death, he married her stepsister Salome Abigail Gsell (1723–1794).

Leonhard Euler died on 18 September 1783 in St Petersburg, Russia. In the morning, he had – as usual – taught one of his grandchildren mathematics and made calculations on his slates. Over lunch, he had discussed the orbit of the recently discovered planet Uranus (identified in 1781 by F. W. Herschel [1738–1822]). Around 5pm, while allegedly sipping tea, he had suddenly suffered a stroke and cried out, I am dying, before losing consciousness. He died from a cerebral haemorrhage at 11pm.

EULER’S SCIENTIFIC WORK

There exist over 800 publications by Leonhard Euler in the form of papers, and more than 20 books. During his lifetime, Euler’s mathematical research output averaged about 800 pages a year, which is more than that of any other mathematician.

Euler was theoretically and practically active across a broad spectrum of scientific and technical fields, and he contributed profoundly to almost every branch of the mathematics of the time. Being both one of the greatest scholars and the most prolific mathematician of all time, he did fundamental work in/on mechanics, calculus of variations, analysis, (complex) function theory, trigonometry, geometry, algebra, infinitesimal calculus, differential equations, differential geometry, graph theory and topology (he invented this field with his resolution of the problem named The Seven Bridges of Königsberg), number theory, philosophy (through which he influenced Immanuel Kant), fluid dynamics, hydraulics, artillery and ballistics, marine engineering, astronomy, orbits of planets and comets, lunar motion (which was helpful for navigation), geodesy, optics, the wave theory of light, the theory of sound, acoustics, elasticity, and possibly others.

Moreover, Euler introduced the concept of the modern textbook, which leads systematically from the simple basics to the forefront of research, incorporating his and others’ work. Combining excellent teaching methods with a clear style, his textbooks could still be used today; in particular, his two-volume algebra book Vollständige Anleitung zur Algebra (Complete Instructions on Algebra) from 1770. However, he wrote most of them in Latin (though he wrote in French and Russian too). Euler did not mean to impress or hide facts, but he wanted to be understood, and he did indeed succeed in presenting highly complex things in an intelligible form.

The theory of pipe flow that Euler had developed while working on the Sanssouci water fountain project led to his formulation in 1755 of the general equations of motion for inviscid fluids, which are known as the Euler equations. In the first half of the 19th century, friction was taken into account, which turned Euler’s equations into the general equations of motion for viscous fluids: the Navier-Stokes equations. These are the foundation of the theory of fluid flow (fluid dynamics).

Das Studium der Werke Eulers bleibt die beste Schule in den verschiedenen Gebieten der Mathematik und kann durch nichts anderes ersetzt werden.

(Studying the works of Euler remains the best training in the various fields of mathematics and cannot be replaced by anything else.)

– C. F. Gauß (1777–1855)

CH2: 1

Euler’s residential address in Berlin from 1743–1766; commemorative plaque

> Behrenstraße 21–22, Mitte (Map 2:12)

In 1907, on the occasion of what would have been Leonhard Euler’s 200th birthday, a bronze plaque was installed here at Behrenstraße 21–22, the house in which Euler had resided from 1743 until he left Berlin in 1766. In 1912, the original house was replaced by today’s building, which – after alterations – has housed the Bayerische Landesvertretung (Representation of the Land Bavaria) in Berlin since 1998, and the plaque that commemorates Euler’s stay at this address was installed at the new building.

The plaque at Euler’s former residential address in Mitte.

CH2: 2

Euler’s former country estate

> Alt-Lietzow, Charlottenburg (Map 6:2)

In 1753, Leonhard Euler bought a large manor in the village of Lietzow (or Lützow), which was then a part of the town of Charlottenburg (which is now a part of Berlin). The motive was to be able to supply his rather large family with fresh produce at a reasonable cost; the (main) residence of the Euler family remained the one in Behrenstraße in Berlin-Mitte (see 1).

During the Seven Years’ War, in 1760, Euler’s Lietzow estate was