Jan Guichelaar – författare

Founded in 1961 and still thriving today, the recreational magazine Pythagoras has given generations of high school students in the Netherlands a perspective on many branches of mathematics that are not taught in schools. This book is a selection of the best and most inspiring articles from Pythagoras magazine. It contains a mix of problems - some easy, some challenging, always original - as well as playful introductions to subjects in algebra, geometry, topology, number theory, and more. Concepts like sudoku and the magic square are given a whole new dimension. Articles on Escher's 'impossible objects', a recurring subject over the years, are part of a special section on mathematics and art. Smart high school students and anyone else with a sharp and inquisitive mind will find in this book a treasure trove rich enough to keep one's mind engaged for many weeks and months.

This is a thorough, very readable and excellently illustrated biography of Willem de Sitter (1872-1934), one of the most influential astronomers of his time, and also a co-author and correspondent of Einstein.