With his wild hair, merry eyes, baggy T-shirt and sockless ankles, Albert Einstein (1879–1955) looked the way the world wants a scientist to look. ‘Why does everybody love me when nobody understands me?’ he puzzled. Some of the explanation for his celebrity may lie in a gift for aphorism that has been compared to Oscar Wilde's.

As Walter Isaacson reminds us in this brilliant biography, rich with newly available archival material, Einstein was unquestionably a genius. His great discoveries were the result of ‘thought experiments’. No equipment needed. Just an empty room and time to think. What might it be like to ride at the speed