沧海桑田 The sea turns into farmland
Explanation
这个成语用来比喻世间万物变化很大，如同大海变成桑田，桑田变成大海一样。
This idiom is used to describe the great changes of all things in the world, just as the sea can turn into farmland and farmland can turn into the sea.
Origin Story
传说，很久以前，东海边住着一位名叫麻姑的美丽仙女。有一天，她与一位名叫王远的仙人相约到朋友蔡经家去饮酒。王远很快便到了蔡经家，却没有看到麻姑的身影。于是，他便派人去请麻姑。麻姑来到蔡经家后，对王远说，她奉命去巡视蓬莱仙境，三次看到东海变成桑田，现在海水又退去了一半。王远感叹地说：“那里又要扬起尘土了。”麻姑笑着说：“不，那里还会变成大海。”麻姑的这句话告诉我们，世事变幻无常，沧海桑田，变化无穷，我们要以积极的心态面对人生的各种变化。
Legend has it that long ago, there was a beautiful fairy named Ma Gu who lived by the East China Sea. One day, she made an appointment with a hermit named Wang Yuan to go drinking at her friend Cai Jing's house. Wang Yuan arrived quickly at Cai Jing's house, but he didn't see Ma Gu. So, he sent someone to fetch Ma Gu. When Ma Gu arrived at Cai Jing's house, she told Wang Yuan that she had been ordered to inspect the fairyland of Penglai. She had seen the East Sea turn into farmland three times, and now the seawater had receded by half. Wang Yuan sighed,
Usage
这个成语用来比喻事物变化很大，常用于形容时代、社会、科技等的快速发展。
This idiom is used to describe the great changes of things, often used to describe the rapid development of times, society, technology, etc.
Examples
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历史的进程就像沧海桑田，充满了变革与发展。
li shi de jin cheng jiu xiang cang hai sang tian, chong man le bian ge yu fa zhan.
The course of history is like the sea turning into farmland - full of change and development.
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人生一世，如白驹过隙，沧海桑田，唯有珍惜眼前。
ren sheng yi shi, ru bai ju guo xi, cang hai sang tian, wei you zhen xi yan qian.
Life is like a fleeting glimpse of a white horse passing by, the world changes like the sea turning into farmland - only the present moment is worth cherishing.
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时代在变，社会在变，科技在变，一切都在沧海桑田般变化着。
shi dai zai bian, she hui zai bian, ke ji zai bian, yi qie dou zai cang hai sang tian ban bian hua zhe.
Times are changing, society is changing, technology is changing, everything is changing like the sea turning into farmland.