Zhang Sixun facts for kids
Zhang Sixun (born in the 10th century) was a brilliant Chinese astronomer and engineer. He lived during the early Song dynasty (960–1279 AD) in a place called Bazhong, Sichuan. Zhang Sixun is famous for creating an amazing armillary sphere for his astronomical clock tower. This special clock used liquid mercury instead of water to keep time!
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Life of an Inventor
Zhang Sixun was very smart. He passed tough government tests in astronomy and math. Because of this, he got a job at the national astronomical observatory. This was a place where scientists studied the stars and planets.
Within just two years, around 977 or 979 AD, Zhang Sixun finished building his incredible armillary sphere. This was a big achievement, and he was rewarded for his hard work.
Building on Others' Ideas
Zhang Sixun was innovative, but he also learned from inventors who came before him. For example, a clever scientist named Zhang Heng (who lived from 78–139 AD) invented the first armillary sphere that used water power. Later, a Buddhist monk and engineer named Yi Xing (683–727 AD) improved on this. He added a special part called an escapement mechanism. This part helps a clock tick steadily and accurately.
Zhang Sixun took these ideas and added his own clever twists. His astronomical armillary sphere and clock were quite similar to one built later by a statesman named Su Song (1020–1101 AD). Both clocks used wheels and gears. Zhang Sixun's clock also had 19 small figures that would pop out to announce the hours and quarter-hours by ringing bells or beating a drum!
Why Mercury Was Key
One of Zhang Sixun's most important ideas was using liquid mercury in his clock instead of water. Older water clocks often had problems in winter because water would freeze. When water froze, the clock would stop working or become inaccurate.
Mercury, however, does not freeze easily. By using mercury, Zhang Sixun made sure his clock could run smoothly and keep accurate time even during the coldest parts of winter. This was a huge improvement! Later clocks, even in the Ming dynasty, also looked for ways to avoid freezing, sometimes using falling sand instead of water.
After Zhang Sixun passed away, no one could quite copy his amazing mercury-powered clock. It was a unique invention, much like Su Song's famous clock tower, which also couldn't be easily replicated after his time.
How His Amazing Clock Worked
Historical records from the Song Shi (written in 1345 AD) tell us more about Zhang Sixun's incredible clock.
His clock was built inside a tower that was more than ten feet tall. All the complex machinery was hidden inside. The top of the tower was round, like the sky, and the bottom was square, like the earth.
Inside, there were many wheels, shafts, and gears. These parts worked together to make the clock move. There were also special bearings to hold everything in place and coupling devices, including the escapement mechanism, which helped the clock keep steady time.
The clock had seven small figures that would ring bells and beat a drum to mark the passing of the quarter-hours. Every day and night (24 hours), the machinery would complete one full rotation. This showed how the sun, moon, and planets moved across the sky.
Other wooden figures would appear every two hours, holding tablets that showed the current time. The clock could even adjust for the different lengths of days and nights throughout the year. It showed how the sun's movement caused changes in temperature, from hot to cold.
The power for the clock came from liquid, just like older clocks by Zhang Heng and Yi Xing. But those older clocks often rusted, and their water would freeze in winter. Zhang Sixun's genius was using mercury instead. This meant his clock worked perfectly all year round, without errors caused by cold weather.
His clock also had models of the sun and moon that moved automatically. Before, people had to move these by hand each day. This automatic movement was considered truly marvelous! Zhang Sixun was seen as being as skilled as the best clock-makers of the Tang dynasty.
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