How likely is it that the Sun will rise tomorrow?
This is more a philosophical question than a scientific one, and it's something we've been muddling over for 250 years.
Asked by: Paul Rhodes, Mansfield
This is one of those questions with hidden depth, and it's fascinated philosophers ever since David Hume pondered it around 250 years ago. That's because it raises the question of how we turn past experience into belief about the future - or, as philosophers call it, the Problem of Induction. In the case of the rising Sun, we use induction to turn the fact that the Sun has risen for the last few billion years to conclude it will rise tomorrow. Hume pointed out, however, that there's no guarantee that something won't go wrong with the Sun overnight to prevent sunrise. He therefore concluded that induction is just a handy rule of thumb that cannot be rigorously demonstrated. Whether Hume was right or not continues to be hotly debated among philosophers to this day.
Robert is a science writer and visiting professor of science at Aston University.