From Quarks to Quasars
June 24 at 7:01 PM ·Get ready for shortest days on record as Earth spins unusually fast on July 9, July 22, and August 5.
Earth is a pretty reliable clock – each full rotation takes about 86,400 seconds, or exactly 24 hours. But it’s not perfect. Since 2020, atomic clocks have revealed something strange: the planet has been spinning slightly faster than usual, shaving off tiny slivers of time.
These changes are measured in milliseconds – thousandths of a second – and tracked using ultra-precise atomic clocks. In 2020, the shortest day ever recorded was just 1.47 milliseconds shorter than normal. Since then, Earth has kept breaking its own records. The shortest day yet came on July 5, 2024, clocking in at 1.66 milliseconds under the 24-hour mark.
And it’s happening again: Scientists predict that Earth will approach record-short days around July 9, July 22, and August 5, 2025.
Why is this happening? That’s the mystery. While the Moon’s position influences short-term spin changes, the long-term acceleration is likely driven by complex motions in Earth’s core. But even leading experts admit they don’t fully understand what’s going on beneath our feet.
For now, Earth remains an unpredictable – and surprisingly fast – timekeeper.
Learn more: https://www.timeanddate.com/.../earth-fast-rotation-2025
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