A Little Tribute to Leonhard Euler

300 years ago last Sunday Leonhard Euler was born. The event is being celebrated in Basel this week. With Newton, Archimedes and Gauss he is generally considered to be one of the four pre-eminent mathematicians in history. Today I've been reading the book Leonhard Euler: Life, work and Legacy. It is a series of academic essays. Euler seems to have been a genial man, kind to the humans he found around him, not terribly interested in stirring up controversy and, of course, a genius.

One of the many things he demonstrated, from observations from various geographical expeditions, was that the earth was an oblate spheroid (flattened on the top, rather like a mandarin orange) - just as Newton had thought - rather than the elongated spindle favoured by the followers of Descartes (the Cartesians).

Euler was born in Basle, educated in Germany and spent his working life in St Petersburg with an interim period in Berlin where he seems to have done a lot of his most important work. He was an incredibly productive man and left a huge legacy of publications behind him. One of the most interesting was a compilation of 'Letters to a German Princess'. The princess concerned was a girl of fifteen called Charlotte. In these letters (about two a week from April 1760- May 1763) he wrote about science and philosophy and they are a valuable example of the popularisation of science of the time. It sounds to me that Charlotte was quite lucky - if she had managed to ingest all of this information she would have been incredibly well educated - but wonder if she appreciated her opportunity.

'Charlotte?'
'What?'
'A letter's come for you.'
'Another one? Is it from Berlin?'
'Yes.'
'Ah. Maybe I'll open it later.'

By the end of his life Euler was blind. He lost his first eye to an abscess in middle age and his second eye after an operation to remove a cataract became infected. But by this time he had declared sight to be a distraction. His memory was phenomenal and apparently at the age of 16 he could recite long passages from Virgil's Aeneid by heart and at the age of seventy he still knew the work in its entirety. This photographic memory was particularly useful once he was blind because he could remember and follow entire tracts of mathematical expressions that his students read out to him which enabled him to continue working well into old age.

On the day of his death ( September 18th 1783) he gave his grandson a maths lesson, made mental calculations on how high a hot air balloon could rise, discussed the orbit of the planet of Uranus and then had his tea. It was then that his pipe fell from his hand. He stooped to pick it up but rose again empty handed. Then, clapping both hands to his chest he exclaimed 'I am dying' and collapsed. As usual he was right. He died about six hours later without regaining consciousness.

Having a memory like Euler's must be very useful in many professions. My brother has always been good at remembering the most obscure facts and then regurgitating them at will. I, in contrast, frequently have trouble remembering the end of a sentence I have just begun. Somehow I lose interest in it and my mind wanders...And just as I finish writing this remember where I first read about Euler - in that Draaisma book about life speeding up as we get older. Which is all about memory, ironically enough.