Humans have been measuring time for a relatively short period in our long history. The desire to synchronize our activities came about 5,000 or 6,000 years ago as our nomadic ancestors began to settle and build civilizations [source: Beagle]. Before that, we divided time only into daylight and night, with bright days for hunting and working and dark nights for sleeping. But as people began to feel the need to coordinate their actions, to be prompt for public gatherings and such, they needed a unified system of keeping time.
Of course, scientists will tell you that we're fooling ourselves if we think we're really keeping track of time. Albert Einstein said "the distinction between past, present and future is only a stubbornly persistent illusion" [source: AMNH]. His daily walks past the clock tower in Bern, Switzerland, led him to some world-changing ideas on the nature of time that we'll look at later.
Whether time is real or not, the measuring of time has become vital to our lives. Over the centuries, people have come up with some creative methods of timekeeping, from the most basic sundials to the cesium-powered atomic clocks of today. In this article, we'll take a look at a variety of methods, including one from China that uses your sense of smell to tell you the time and others that are as old as time itself.