A group of scientists tracking the Earth’s rotation predicts that today will be slightly shorter than normal due to variations in the planet’s spin. According to the International Earth Rotation and Reference Systems Service, July 22 is expected to come out about a millisecond short of a standard 24-hour spin.
This variation is not uncommon, as the Earth’s rotation has been influenced by factors such as the gravitational pull of the moon, winds, and atmospheric conditions for thousands of years. Researchers use data from radio telescopes pointing at quasars, GPS systems, and observations of solar eclipses to forecast the day length.
Over millions of years, the Earth’s rotation has been slowing down due to the moon’s effect on ocean tides, a process known as “tidal braking.” However, recent days have seen shorter-than-normal spins, with last year’s shortest day being 1.65 milliseconds shorter than usual.
While these variations are not significant in themselves, they raise questions about the possibility of instituting “negative leap seconds” – taking away a second rather than adding one. However, most experts believe that this would be unlikely due to the growing trend towards regular “leap seconds.”
Understanding and predicting the Earth’s rotation is crucial for various applications, including navigation, missile launches, and high-tech farming. Climate change, in particular, has been found to be influencing the planet’s rotation by melting ice at the poles and redistributing water, which can lengthen days.
Despite these variations, scientists continue to monitor the Earth’s rotation to improve predictions and adapt to changing conditions.
Source: https://www.npr.org/2025/07/22/nx-s1-5475167/hurry-up-scientists-predict-today-will-be-slightly-shorter-than-normal