From - Sky & Telescope, By - Bob King Edited by -Amal Udawatta, The Big Dipper ascends the evening sky at nightfall in mid-March. Using Polaris and the Dipper's Pointer Stars, you can make a simple clock. Bob King Time-telling goes way back. Early humans watched the daily and nightly perambulations of the Sun and Moon to mark the passage of time. Even the shadow of a stick jabbed into the ground could serve as a primitive clock. The earliest manufactured timekeeping devices were sundials and water clocks. In a water clock, water dripped through a hole in the bottom of one container into another. Tower clocks that marked the hour by sounding bells appeared in the late 13th century. Clocks with familiar faces and hands made their appearance in the 1700s. Three hundred years later, cell phones and digital clocks help us keep track of the time. Cell phones get their time directly from Global Positioning (GPS) satellites or through the nearest cell tower, which also uses GPS. Eac