Water clocks, known as a clepsydra in Ancient Greece, were widespread for centuries, and the philosopher Plato is credited with first adapting one into an alarm in the 5th Century BC. He trapped air inside a vessel which water was flowing into; as the water increased so did the pressure, eventually resulting in a loud kettle-like whistle. Water clocks were also some of the earliest automated village bells, notes Champion. They used large basins of water which when drained would lead to the striking of a bell – one 12th Century chronicle records such a water reservoir being used to put out a fire.
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Photograph: Ryan Waniata
When my son was in first grade, he came home from school in tears saying that he hated math. My wife and I are both engineers, so this was the sort of all-hands-on-deck shock that demanded our immediate attention. Before this my son had loved math. He would demand that we challenge him with math problems to do in his head in the car and over dinner. He loved doing flashcards. He played math games on his tablet unsupervised for hours. Even now, years later in 4th grade, he has decided he wants to learn calculus, so he insisted I start explaining it to him as best I could in the car, and started working through pre-algebra in Khan Academy on his own. How is it possible that a kid like this had decided he hated math?