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Earth's Day Length is Changing: When Will We Reach 25 Hours?

Published December 30, 2025, 12:14
Earth's Day Length is Changing: When Will We Reach 25 Hours?

The Earth's day length is not constant and will not remain at 24 hours forever. Scientists have known for decades that the planet's rotation is gradually slowing down, primarily due to the gravitational interaction with the Moon and the resulting tides. This slowdown, although subtle, leads to a gradual lengthening of the day. The duration of the day has never been perfectly stable, exhibiting small variations recorded through astronomical observations and atomic clocks. International organizations continuously monitor the Earth's rotation to ensure global time remains synchronized with the planet. The slowing is caused by the loss of rotational energy due to tidal forces, which are not perfectly aligned with the Moon. Based on current trends, estimates suggest that the Earth will reach 25-hour days in approximately 200 million years. This change occurs on a geological and astronomical timescale and is not expected to directly impact human civilization or our calendars. However, monitoring the Earth's rotational speed is crucial for maintaining the accuracy of global time and understanding the complex interactions between the Earth and the Moon.