In ancient Greece, people used a Clepsydra or water clock to measure the passage of time. Before we started this project we had so many questions: When was it invented? What was it made out of? How did it work? When and where the first water clock was made is not known but some historians believe that the Chinese had them as long ago as 4000 BC. The first water clocks in Greece appeared about 400 BC. When the Greeks found that water flowed at a constant rate, they knew it would be a reliable way to measure time. They made a simple clay jar with hour markings on the sides. Then another clay pot with a hole at the bottom and filled with water would be at the top of it. The water from the upper pot would simply drip into the measuring pot. When the water rose, it would reveal the time of day it was according to the markings. Pretty cool right? So, we here at the Galileo School made our own version of a Greek water clock. We took a couple of books, a milk jug (empty of course) and an empty glass salsa jar. We stacked up the books and put a very small hole in the milk jug then covered it with tape. Then we filled the milk jug with water and put it on top of the stacked books. Next we put the salsa jar underneath the raised jug of water. We then took the tape off the hole in the jug and started a stopwatch. Exactly when a minute passed, Payton made a mark on the jar exactly where the surface of the water was. She made a mark for every minute that passed until the jar was filled. Even though our “clock” only measured up to three minutes we proved that the water clock is accurate, and the flow of water is constant because of the gravitational pull of the earth. Over time water clocks were improved. The Greeks further advanced water clock design to include an early feedback system and gearing that resulted in improved accuracy. We love to do these kind of projects and we hope to do more like them!