In Clocks and More Clocks, the protagonist Mr. Higgins has a problem. He has a clock on every floor of his four-storey house, but when he goes around the house to check on them, they each show him a different time. Yet when he asks a clockmaker for help, he is told that they are all in perfect working order. What’s going on?

  
While the premise of this Pat Hutchins classic is deliberately silly, it’s a brilliant way to illustrate a fundamental understanding of time itself — i.e. it ticks along even when you are not looking at a clock.