The article traces the evolution of time measurement from ancient civilizations to modern atomic clocks. Initially, time was measured indirectly as intervals between events. Ancient Egyptians and Greeks made early attempts at dividing time into standard units, but it wasn’t until the late medieval period that mechanical clocks were developed for fixed prayer and work periods.
The concept of minutes and seconds also has ancient roots, originating from the Sumerians’ division of a circle into 360 degrees, which was later applied to the sky by Babylonian astronomers and Greeks. In the 150s CE, Ptolemy defined the division of each degree into 60 minutes and each minute into 60 seconds in his treatise Almagest.
In modern times, atomic clocks based on the oscillations of atoms have become the most precise timekeeping devices. Cesium clocks define the second by counting 9,192,631,770 microwave oscillations. Modern cesium clocks maintain time to within 1/3,000,000 of a second per year, far surpassing the precision of any mechanical clocks. Additional experimental atomic clocks are even more precise, potentially opening new applications.
The evolution of time measurement demonstrates the importance of accurate timekeeping for coordinating human activities and advancements across various fields. From early mechanical clocks to atomic standards, time has been critical to human progress. The development of increasingly precise atomic clocks represents a key advancement in defining and dividing the second, the international unit of time.
Source: https://www.nist.gov/si-redefinition/second-introduction
Keywords: precise, measurement, atomic clocks
