1 The sundial was one of the first timekeeping devices created, and dates back to ____ Roman and Greek societies. It used a central ____rod, called a gnomon, and the sun's light to cast a shadow onto a platform which was marked to show the hours of the day. 2 The first clepsydra or water-clock was created around 500-600BC, It was widely used in Egypt. Greece and the Arab world. The concept was quite simple and used the naturally consistent movement of water to ____ time. This was done by allowing water to ____, either in or out of a marked container. 3 By far the most modern device on this list, the atomic clock was developed in 1949. It is accurate to a couple of ____ over several million years, making it by far the most ____ timekeeping device to date The atomic clock is incredibly advanced. Amazingly it uses the rotation of subatomic particles to measure the passing of time! 4 Commonly seen even today, the hourglass uses similar ____ to that of a clepsydra. It uses two glass bulbs, one above the other, with a small opening in between. The sand inside gradually falls from top to bottom, indicating that a(n) ____ amount of time has passed. It is believed that it was first created in the 8th century, although it only truly became popular around the 1300s. 5 Obelisks were the next logical step from the sundial, and used the same basic ____. They were towering pointed ____, which cast a shadow across a large public area, similar to how a gnomon did. They made timekeeping easier for wider communities. There are still many famous obelisks around the world today, such as the Washington monument in the USA.

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