While we are used to thinking of a day as lasting exactly 24 hours, the Earth is actually experiencing small but noticeable fluctuations in its rotation speed.
Báo Khoa học và Đời sống•11/07/2025
During July and early August 2025, on July 9, July 22, and August 5, Earth will rotate faster than usual due to the Moon's proximity, shortening days by 1.3 to 1.51 milliseconds. Billions of years ago, the Earth's rotation slowed down as the Moon moved away, lengthening the length of the day to the current 24-hour length.
However, since 2020, scientists have recorded the phenomenon of the Earth's rotation speeding up again, with July 5, 2024 being the shortest since 1970, 1.66 milliseconds short.
In addition to the Moon, human activities such as ice melting and groundwater extraction also contribute to changes in the Earth's rotation speed. Some natural disasters, such as the 2011 Japan earthquake, can also shorten days, even if only by a few microseconds.
However, this difference is too small to affect daily life, and only when the difference exceeds 0.9 seconds, international organizations need to add a "leap second" to calibrate standard time.
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