One of 18th century Europe’s brightest minds, Swiss physicist Leonhard Euler was a pioneering figure in the history of mathematics.
A prominent figure in the growing universities of St Petersburg and Berlin, Euler’s contributions furthered the fields of geometry, trigonometry and calculus for decades, despite him going almost completely blind in later life.
But who exactly was Leonhard Euler?
Early life
Euler was born in Basel, Switzerland on 15 April 1707. His father, Paul III Euler, was a pastor of the Reformed Church, and his mother Marguerite Brucker belonged to a long line of well-known scholars in the classics. Soon after his birth the family moved to the Swiss town of Riehen near Basel, where he spent most of his childhood with his three younger siblings.
As a youth, Leonhard received schooling in mathematics from his father, who had taken courses from the prominent mathematician Jacob Bernoulli at the University of Basel while training to be a Protestant minister. At 8 years old, Leonhard was enrolled in the Latin school in Basel, and at 13 he enrolled in the University of Basel, not an uncommon practice at the time.
Portrait of Bernoulli in volume I of his 1742 ‘Opera omnia’
Image Credit: Bernoulli, Jean, 1667-1748, Public domain, via Wikimedia Commons
There he took a course on elementary mathematics by Johann Bernoulli, the younger brother of Jacob Bernoulli. In his autobiography, Euler later wrote: “the famous professor…made it a special pleasure for himself to help me along in the mathematical sciences”, and despite being too busy to give him private lessons, allowed the young boy to visit him every Saturday afternoon to go over difficulties in his reading.
During this time, Euler was given his father’s permission to set aside the career of pastor and become a mathematician.
Establishing his name
In 1723, Euler received his Master of Philosophy after submitting a dissertation comparing the philosophies of Descartes and Newton, and enrolled in the theological faculty of the university.
Continuing his studies, he wrote a further dissertation on propagation of sound before applying for a position to teach physics at the university. This was rejected.
Instead, he was offered a position at St. Petersburg Academy in Russia, established by Peter the Great in 1724. He had been recommended by Johann Bernoulli’s son Daniel, after his brother Nicholas Bernoulli had sadly died 8 months after taking up the position.
At Bernoulli’s behest, Euler was promoted to the mathematics department in St. Petersburg, and alongside his teaching served as a medical lieutenant in the Russian Navy. It was only after he became a professor and therefore a full member of the academy that he was able to quit this venture.
Swiss stamp with Leonhard Euler, c. 2007
Image Credit: rook76 / Shutterstock.com
In 1733, Daniel Bernoulli left his post as the Senior Chair of mathematics in St Petersburg, due to censorship by the Russian Orthodox Church and disputes over his salary. Euler then took over the position, allowing him to get married.
Family life
On 7 January 1734 he married Katharina Gsell, the daughter of painter Georg Gsell, who would remain his wife for 39 years until her death.
They had 13 children, 5 of which survived childhood, and by all accounts were a happy and loving family. Euler even once claimed to have made some of his best mathematical discoveries while holding a baby or with his children at his feet.
Work in Berlin
By 1740, Euler was renowned for his work and was personally offered a position at the University of Berlin by Frederick the Great of Prussia. Faced with mounting turmoil in Russia, he accepted, arriving in Berlin the following year.
He would spend the next 25 years there in what was his most productive period, writing 380 works (of which 275 were published). His most celebrated is perhaps his Introductio in analysin infinitorum, which laid the foundations of mathematical analysis and introduced the notation for sin(x) and cos(x).
Despite his outstanding academic record, he was passed for the position of President of the Berlin Academy, with Frederick taking the role instead. A simple and devout man, Euler stuck out like a sore thumb at Frederick’s court, who reportedly found him unsophisticated and badly informed on matters outside of mathematics.
Portrait of Frederick the Great by Johann Georg Ziesenis, c. 1763
Image Credit: Johann Georg Ziesenis, Public domain, via Wikimedia Commons
He clashed with the witty Voltaire, who held great standing at court, and the pair were often said to have gotten into lengthy debates at Euler’s expense.
Eventually, Euler was invited to return to St Petersburg following the country’s stabilisation under Catherine the Great, where he returned in 1766.
Blindness
As Euler grew older, his eyesight worsened following a severe and life-threatening fever in 1735. He blamed his vision issues on a period of intense cartographic work in 1738, and by 1740 he had lost all vision in his right eye, to the extent that Frederick the Great called him Cyclops.
Euler however jokingly stated “Now I will have fewer distractions”, and indeed, his productivity did not cease even after going almost completely blind in 1766. He produced half of his entire works during this time with help from his sons, colleagues and his grandson-in-law.
Death
On 18 September 1783, Euler had lunch with his family and was later discussing the newly discovered planet Uranus with a student. Suddenly, he collapsed and died from a brain haemorrhage at around 5pm, aged 76.
Euler was buried next to his wife at the Smolensk Lutheran Cemetery on Vasilievsky Island and in 1957, to commemorate the 250th anniversary of his birth, his tomb was moved to the Lazarevskoe Cemetery at the Alexander Nevsky Monastery.
Following his death, his huge body of work was continuously published for almost 50 years. So vast was the outpouring of his work throughout his life, it has been estimated he was the author of a quarter of the combined output in mathematics, physics, mechanics, astronomy, and navigation in the 18th century.
