In the early 1970s mathematician Donald Knuth spent a sabbatical with his wife in Norway. The time was meant to be spent relaxing. Yet one night he woke up his partner in a state of agitation. He ...

If you've got the time, we've got the riddle. And it's time for a riddle about time: How many numbers are on a clock? It begins with the simplest of questions that, nevertheless, has no simple answer.

Imagine a horizontal line. The very left is marked one thousand and the very right is marked one billion. On this line, where would you add a marker to represent one million? If you said somewhere in ...