The Scientific Invention of Clocks: Liang Lingzhan and Zhang Sui Nowadays we can tell the time just by looking at a clock. We regard this as a natural thing. But for thousands of years, there was no precise way to measure time. People tell time by the position of the sun in the sky, or by devices like sundials or hourglasses. In an hourglass, time is indicated by sand falling from a double-ended glass container. The person who changed the above situation was an outstanding Chinese astronomer named Yi Xing (a monk from the Tang Dynasty, commonly known as Zhang Sui - translation annotation) who lived in the 8th century AD. Together with another Chinese inventor, Liang Lingzhan, he designed the "escapement" device, the set of gear cogs at the center of all mechanical clocks. Mechanical clocks came to Europe in the Middle Ages. By the 14th century, Europe had built mechanical home clocks that were both large and cumbersome. They are driven by clock hammers and are accurate to within approximately one hour per day. Such clocks usually have little trust in people's eyes. They are connected with a bell that tells the time. But since they are so imprecise, there is no point in showing minutes and seconds in a mechanical device! In the 15th century, the German locksmith P. Henlein developed a spring-driven clock, and then in the 17th century, C. Huygens made a more accurate clock with a pendulum in 1656. In 1859, he made a clock in Wis Minster Abbey installed Big Ben, which became the standard for all accurate bell towers. In 1929, quartz crystals were first used for timekeeping, and the error of the observatory's quartz clock was only one ten thousandth of a second per day. The first atomic clock began operation in 1951, with an error of less than one part per billion per day, making it the most accurate clock currently available. In the Middle Ages, clockmakers created clocks that could show the movement of the sun, the phases of the moon and planets, and the time. An anthropomorphic mechanism rang a bell from time to time, announcing the hours and quarters of an hour with a voice.