Vocabulary
dehydration: A condition that happens when your body loses more water than it takes in. 脱水症
heatstroke: A serious illness caused by the body overheating, often due to long exposure to high temperatures.熱中症
precaution: An action taken in advance to prevent danger or harm, 予防策
diuretic: A substance that makes the body produce more urine, which can lead to water loss. 利尿剤
vulnerable: Explanation: Easily harmed or hurt, especially in certain conditions.傷つきやすい
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Watching sports in person is exciting, but summer heat can be dangerous. Extreme heat can cause dehydration, heatstroke, or even death. Both players and fans are at risk. Cases in Korea, England, and Japan show that people of all ages can be affected, even in the shade or on cloudy days. Most illnesses happen in July and August, especially between noon and 3 p.m. To stay safe, check the weather forecast, avoid the hottest hours, and bring plenty of non-alcoholic drinks. Alcohol increases dehydration risk. Children, the elderly, and people with health problems should take extra care or stay home during heat alerts. Organizers can help by preparing safety manuals, training staff, and working with emergency services. If you notice dizziness, nausea, or confusion, move to a cool place, drink water, cool your body, and get medical help immediately.
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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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