Sundials tell time during the day, when it’s sunny. How did the Egyptians tell time at night?
Way back around 1500 bc (over 3,500 years ago) some clever Egyptian invented the water clock so they could tell time at night. A water clock is a jar with sides that taper from a wide brim to a small base. Almost at the bottom is a small hole. The idea is: you fill the jar with water and water leaks out the hole. There are marks on the inside of the jar for every hour. As the water level slowly sinks, it reaches each mark and that’s how you know what time it is.
It sounds like a swell idea, but I have a few problems with it. Number One: I don’t know exactly how big these jars were, but it doesn’t seem like there’d be nearly enough water inside them to last all night long. Even if the hole at the bottom were a mere pinhole, I think the water would run out in an hour. Did they wake up every hour to refill the water clock? That seems like a pain in the neck.
Number Two: to function as an accurate time-measurer, that jar would need to be filled precisely on the hour. You’d need to coordinate with a friend outside looking at a sundial so he could tell you the moment to fill it up.
Number Three: where did the water go after it leaked out? Did they just let it run all over the floor; did they collect it in another jar?
Number Four: Did their dogs see puddles of water on the floor and think, “What the heck, it must be okay to pee in the house now?”
Number Five: Didn’t the sound of dripping water keep them from sleeping?