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... Though we sum up a day as 24 hours and a year as 365 days, Earth's rotational and orbital speeds aren't exactly consistent. Instead, both fluctuate, swayed by atmospheric drag, tidal forces, changes within Earth's core, and the planet's elliptical orbit around the Sun. It's why atomic clocks are so important; without them, the stretching or shrinking of time would be extremely difficult to measure.
Thanks to atomic clocks (and all the worldly forces that influence them), scientists know that Earth's rotation has begun to slow down, thanks in large part to the loss of ice coverage in polar regions. But for a few days this year, our planet will actually spin faster.
On average, a single Earth day is 86,400 seconds. (A controversial leap second is tacked on every now and then to accommodate tiny stretches in astronomical time.) Variations away from this average are measured in milliseconds and referred to as "length of day," or LOD. On June 29, 2022, Earth's angular momentum was so low (and the atmosphere's angular momentum so high) that the planet saw an LOD of -1.59 milliseconds"the shortest day ever recorded.
This year, though, Earth will see three short days, indicating an overall increase in the planet's rotational speed. According to a chart designed by the folks at TimeAndDate.com (based on data from the US Naval Observatory and International Earth Rotation and Reference Systems Service), today, July 9, is predicted to be 1.30 milliseconds shorter (LOD -1.30 milliseconds) than the average day. July 22 has an anticipated LOD of -1.38 milliseconds, while August 5 corresponds to an LOD of -1.51 milliseconds.
Part of this is because of the Moon's position relative to Earth on those days. Our planet spins faster when the Moon "pulls" it from the poles, not the equator, and on July 9, July 22, and August 5, the Moon will be closer to the former. It certainly helps that the distribution of Earth's mass is trending equatorial, too; as polar ice melts into the world's oceans, there's less mass at the "top" and "bottom" of Earth for the Moon to tug on, and the planet can spin more freely on its axis.
Of course, we won't notice the changes to Earth's rotational speed. ...
