Brain‑Melting Discovery: Why July 9’s Record‑Breaking Earth Spin Could Crash Your Clock—and What Experts Are Doing About It
On July 9, 2025, Earth’s length of day was predicted to be −1.30 ms, the fastest day of 2025 and close to 2024’s all‑time −1.66 ms. A 1 millisecond timing error can yield GPS position errors of hundreds of meters and disrupt high‑frequency trading algorithms. Leading explanations for the spin‑up include an unusual Moon alignment, deep core fluid motions, and mass redistribution from melting ice. Future ultra‑short days are forecast for July 22 and August 5, 2025. The International Earth Rotation and Reference Systems Service may introduce the first negative leap second as early as 2029. More than 450 cesium
