millisecond ミリ秒, 1秒の1000分の1を表す非常に小さな時間単位。
precise精密な
gravitational pull 重力の引力
leap second: うるう秒, 地球の自転速度の変化に合わせて、標準時を調整するために加えられる1秒。
subtract 引く／差し引く
Antarctica 南極大陸）、氷に覆われている。

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This summer, Earth is spinning a little faster than before, making days slightly shorter. On July 10, 2025, the day was 1.36 milliseconds shorter than usual. While we can’t feel these changes, they affect atomic clocks, GPS systems, and the internet, which rely on very precise time.

The length of a day can change slightly because of the Moon’s gravitational pull, weather patterns, and movement inside the Earth’s core. Scientists use atomic clocks to measure time accurately. In the past, they sometimes added a “leap second” to adjust the time, but now, for the first time, they may need to subtract one instead.

Climate change and melting ice in places like Antarctica and Greenland can also change how Earth spins, just like a skater spinning faster when pulling their arms in. It’s still difficult to predict how Earth’s speed will change in the future.
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