Leonhard Euler's Letters to a German Princess

Leonhard Euler wrote 234 letters in French to Princess Friederike Charlotte of Prussia over two years starting in 1760. The letters were first published in 1768 and 1774, with later editions adding more planetary information. In the letters, Euler discusses concepts like magnitude and extension, using examples like the distance between cities and the size of celestial bodies. He also explains the idea of velocity, comparing speeds of different modes of transportation and natural phenomena like wind and sound. Euler's letters aim to educate the princess on various mathematical and scientific principles in a clear and engaging manner. The letters provide insights into Euler's teaching methods and his ability to explain complex ideas in a simple and understandable way, making them valuable educational resources.