|
Lebih lanjut, Euler diminta untuk menjadi tutor bagi [[:en:Friederike Charlotte of Brandenburg-Schwedt|Friederike Charlotte dari Brandenburg-Schwedt]], putri bangsawan [[:en:Anhalt-Dessau|Anhalt-Dessau]], yang adalah keponakan perempuan Frederick. Euler menulis lebih dari 200 surat kepadanya pada awal tahun 1760-an, yang kemudian dikumpulkan menjadi suatu volume terlaris berjudul ''[[:en:Letters to a German Princess|Letters of Euler on different Subjects in Natural Philosophy Addressed to a German Princess]]''.<ref name='Digital Copy of "Letters to a German Princess"'/> Karya ini memuat penjelasan Euler mengenai berbagai topik fisika dan matematika, selain juga pandangan berharga mengenai kepribadian dan kepercayaan agama Euler. Buku ini menjadi lebih banyak dibaca daripada karya-karya matematikanya, dan diterbitkan di seluruh Eropa dan Amerika Serikat. Kepopuleran buku ini membuktikan kemampuan Euler untuk menyampaikan hal-hal ilmiah secara efektif bagi orang awam, suatu kemampuan yang jarang ditemukan pada ilmuwan-ilmuwan peneliti yang berdedikasi.<ref name="Friedrich"/>
Meskipun Euler banyak berkontribusi bagi prestasi Akademi Berlin, ia akhirnya tidak disukai oleh [[Friedrich II dari Prusia|Friedrich]] dan harus meninggalkan Berlin untuk kembali ke St. Petersburg.
Meskipun Euler banyak berkontribusi bagi prestasi Akademi Berlin, ia akhirnya dimusuhi oleh [[Friedrich II dari Prusia|Friedrich]] dan harus meninggalkan Berlin.<!-- The Prussian king had a large circle of intellectuals in his court, and he found the mathematician unsophisticated and ill-informed on matters beyond numbers and figures. Euler was a simple, devoutly religious man who never questioned the existing social order or conventional beliefs, in many ways the polar opposite of [[Voltaire]], who enjoyed a high place of prestige at Frederick's court. Euler was not a skilled debater and often made it a point to argue subjects that he knew little about, making him the frequent target of Voltaire's wit.<ref name="Friedrich"/> Frederick also expressed disappointment with Euler's practical engineering abilities:
{{quote|I wanted to have a water jet in my garden: Euler calculated the force of the wheels necessary to raise the water to a reservoir, from where it should fall back through channels, finally spurting out in [[Sanssouci]]. My mill was carried out geometrically and could not raise a mouthful of water closer than fifty paces to the reservoir. Vanity of vanities! Vanity of geometry!<ref name=fredlett/>}}
-->
[[Image:Leonhard Euler.jpg|thumb|Lukisan portret Euler pada tahun 1753 karya [[:en:Emanuel Handmann|Emanuel Handmann]], menunjukkan masalah pada mata kanan Euler, kemungkinan [[:en:strabismus|strabismus]]. Mata kiri Euler yang saat itu nampak sehat kemudian terkena [[katarak]].<ref name="blind"/>]]
<!--
=== Penyakit mata ===
Euler's [[ eyesightPenglihatan]] worsenedEuler throughoutterus hismemburuk mathematicalsepanjang careerkarier matematikanya. InPada tahun 1738, threetiga yearstahun aftersetelah nearlyhampir expiringmati fromakibat fever, he became almost blind in his rightdemam eyetinggi, butmata Eulerkanannya ratherterkena blamedinfeksi thedan painstakinghampir worksama onsekali [[cartography]] he performed for the Stbuta. PetersburgSelama Academytinggal fordi hisJerman, condition.ia Euler'shanya visionbisa inmelihat thatdengan eyemata worsenedkiri. throughoutTidak hisberapa staylama insetelah Germany,tiba todi the extent that Frederick referred to him as "[[Cyclops]]"St. EulerPetersburg, latermata developedkirinya aterkena [[ cataractkatarak]] in his left eye, which was discoveredpada intahun 1766. JustHanya abeberapa fewminggu weeks after its discoverysetelahnya, heia wasmenjadi renderedbuta almost totally blindtotal. HoweverNamun, hisproduktivitasnya conditionmalah appearedmeningkat toberkat haveingatannya littleyang effectluar on his productivity, as he compensated for it with his mental calculation skills and exceptional memorybiasa. Upon losing the sight in both eyes, Euler remarkedberkata, " NowSekarang Iperhatianku willlebih havesedikit fewer distractionsgangguannya".<ref>[https://books.google.ca/books?id=KUYLhOVkaV4C&pg=PA17&lpg=PA17&dq=%22now+i+will+have+fewer+distractions%22&source=bl&ots=cELiNguUQ9&sig=vGQmYpZ7EUbtpOyh8CIb3uDCgh8&hl=en&sa=X&ved=0ahUKEwiX6c_V7KLSAhWH6YMKHabkCbYQ6AEILjAE#v=onepage&q=%22now%20i%20will%20have%20fewer%20distractions%22&f=false]</ref> ForDalam examplekeadaan buta, Euler coulddapat repeatmengatakan theisi ''[[Aeneid]]'' ofkarya [[Virgil]] fromdari beginningawal tosampai endakhir withouttanpa hesitationragu-ragu, anddan foruntuk everysetiap pagehalaman inedisi theitu editionia hedapat couldmenunjukkan indicatebaris whichpertama linedan wasbaris the first and which the lastterakhir. WithDengan thebantuan aidseorang ofjuru his scribestulis, Euler'sia productivitysemakin onbanyak manyberkarya areasdalam ofberbagai studybidang actually increasedilmu. HeRata-rata produced,ia onmenerbitkan average,satu oneartikel mathematicalmatematika papersetiap everyminggu weekpada in the yeartahun 1775.<ref name="volumes"/> <!--The Eulers bore a double name, Euler-Schölpi, the latter of which derives from ''schelb'' and ''schief'', signifying squint-eyed, cross-eyed, or crooked. This suggests that the Eulers may have had a susceptibility to eye problems.<ref>{{cite book |last=Calinger |first=Ronald |date=2016 |title=Leonhard Euler mathematical genius in the Enlightenment |url=http://press.princeton.edu/titles/10531.html |location= |publisher=Princeton University Press |page=8 |isbn=9781400866632 }}</ref> ▼
▲Euler's [[eyesight]] worsened throughout his mathematical career. In 1738, three years after nearly expiring from fever, he became almost blind in his right eye, but Euler rather blamed the painstaking work on [[cartography]] he performed for the St. Petersburg Academy for his condition. Euler's vision in that eye worsened throughout his stay in Germany, to the extent that Frederick referred to him as "[[Cyclops]]". Euler later developed a [[cataract]] in his left eye, which was discovered in 1766. Just a few weeks after its discovery, he was rendered almost totally blind. However, his condition appeared to have little effect on his productivity, as he compensated for it with his mental calculation skills and exceptional memory. Upon losing the sight in both eyes, Euler remarked, "Now I will have fewer distractions".<ref>[https://books.google.ca/books?id=KUYLhOVkaV4C&pg=PA17&lpg=PA17&dq=%22now+i+will+have+fewer+distractions%22&source=bl&ots=cELiNguUQ9&sig=vGQmYpZ7EUbtpOyh8CIb3uDCgh8&hl=en&sa=X&ved=0ahUKEwiX6c_V7KLSAhWH6YMKHabkCbYQ6AEILjAE#v=onepage&q=%22now%20i%20will%20have%20fewer%20distractions%22&f=false]</ref> For example, Euler could repeat the ''[[Aeneid]]'' of [[Virgil]] from beginning to end without hesitation, and for every page in the edition he could indicate which line was the first and which the last. With the aid of his scribes, Euler's productivity on many areas of study actually increased. He produced, on average, one mathematical paper every week in the year 1775.<ref name="volumes"/> The Eulers bore a double name, Euler-Schölpi, the latter of which derives from ''schelb'' and ''schief'', signifying squint-eyed, cross-eyed, or crooked. This suggests that the Eulers may have had a susceptibility to eye problems.<ref>{{cite book |last=Calinger |first=Ronald |date=2016 |title=Leonhard Euler mathematical genius in the Enlightenment |url=http://press.princeton.edu/titles/10531.html |location= |publisher=Princeton University Press |page=8 |isbn=9781400866632 }}</ref>
-->
|
