1. Time-Keeping: Water Clocks By: Toan Luong (thl5045) Tyler Feng (tpf5081)

2. Time-Keeping Since ancient times, people have realized how important it is to keep track of time. Even in many of the earliest civilizations discovered, evidences of time-keeping methods were found.

3. Sundials Sundial is a type of time-keeping device that utilizes the Sun to keep track of time. The sun casts a shadow from its style onto a surface marked with lines indicating the hours of the day.

4. Problem Despite how great the concept behind this device was. When there is no sunlight, it is impossible to tell time with a sundial. Therefore, the people of ancient time faced a problem. How are they going to know the time during the night ? Solution Due to the limitation that the Sundial poses, the Water Clock was invented in order to view time more conveniently.

5. The Earliest Water Clock The oldest water clock found was dated to be around 1417-1379 BCE, during the reign of Amenhotep III where it was used in the Temple of Amen-Re. (I tried to look for a photo, however, I could not find any photo of that specific water clock mentioned above)

6. Types of Water Clock There two distinctive types or water clocks. One of them is called the outflow water clock and the other one called inflow. The differenced are based on the way liquid moves in relationship to the primary vessel.

7. Outflow Water Clock Time is measured with an outflow water clock by filling a vessel with water and slowly draining it away at as even a rate possible. Markings inside the vessel are observed to gage how much time passes. This type of water clock is similar to the clepsydras used in ancient Greece around 325 B.C. Greek clepsydras were stone bowls with sloping sides that permitted water to drip at a nearly constant rate from a small hole near the bottom.

8. Inflow Water Clock An inflow water clock works in the reverse manner as the outflow model. This type of water clock uses liquid to fill up a container rather than drain it away. As the water rises, time can be measured against hour and minute marks made inside the vessel. Some designs of inflow water clock is still used to this day in parts of North Africa. For example the Persian water clock, which is a metal bowl with a hole in the bottom is set within a larger body of water, and as the water seeps slowly into the bowl, it sinks within a set amount of time.

9. Impact on Society The water clock marked a milestone in the history and development of timekeeping devices. It was a success for people during that time since it enabled the ability to keep-time when there is no sunlight. In which proved itself to be very useful during its time. Despite being such a simple device compared to the technology today, some water clock designs are still in use to day.

10. Problem Even-though the water clock was ground breaking and successful, there were problems with it. The most significant issue is the difficulty to control the water flow accurately (changes in temperature affect liquid flow, etc), and therefore, both types of water clocks have a varying margin of error.

11. The End

12. Sources http://www-groups.dcs.st- and.ac.uk/~history/HistTopics/Water_clocks.html http://www-groups.dcs.st- and.ac.uk/~history/HistTopics/Water_clocks.html http://en.wikipedia.org/wiki/History_of_timekeeping_devices http://en.wikipedia.org/wiki/Sundial http://www.ask.com/history/water-clocks-work-94c825812fff0b89