History of Time

18 History of Time Long ago, humans lived a nomadic life, wandering from place to place. When the sun came up, people began to gather food. When the sun went down, they went to sleep for the night. All of that changed once they began to settle and develop towns. At this point, they needed a way to tell time. This is when the first useful time-telling tool was invented: the sundial. As the sun travelled across the sky, it cast shadows on the face of the sundial. Using these shadow marks, it was possible to get a general idea of the time of the day. The hourglass was another basic time-telling tool. It consisted of two glass containers connected by a narrow glass tube. As sand flowed from the top glass container through the narrow neck to the bottom glass container, it was possible to get a general idea of the time.

Different types of water clocks were invented next. A measured substance (this time, water) flowed out of one container into another container. When all of the water had flowed into the second container, people would know that a specific amount of time had passed. In the 11th century, mechanical clocks were invented, but they weren't very accurate. They lost fifteen minutes each day. Mechanical clocks became more accurate when small springs were added to move the hands of the clock. As a result of this invention, clocks became smaller and for the first time, watches were built using this spring system. Over the next 300 years, many improvements were made to clocks. Mass production made them increasingly cheaper. Soon many people could afford a clock or watch. By the 1950s, digital watches were invented. The measurement of time had entered the modern age. In 1967, the atomic clock was developed. In 1999, further improvements were made. The atomic clock is now accurate to within one second every twenty million years. An early caveman looked up at the sun to get a general idea of the time of day. Physicists in the 21st century use atomic clocks to assist them with important experiments. The history of time is indeed the history of human advancement.