Yrjö Väisälä (6 September 1891 - 21 July 1971) was a Finnish astronomer and physicist. His main contributions were in the field of optics, but he was also very active in geodetics, astronomy and optical metrology. He had even an affectionate nickname of Wizard of Tuorla (Observatory/Optics laboratory), and there is a book with the same title in Finnish describing his works. Read more