Earth’s rotation is speeding up. This summer, our planet will spin faster than usual, creating the shortest day since records began. Though we cannot sense these changes, they show the forces that reshape our world.
Most people assume days last exactly 24 hours, but Earth’s spinning speed changes constantly. Scientists found our planet completing rotations faster than ever before. July 9, 2025, broke all previous records, while July 22 and August 5, 2025, will each be between 1.3 and 1.51 milliseconds shorter than normal.
July 9 Breaks All Previous Marks
On July 9, the planet completed its rotation 1.3 to 1.6 milliseconds quicker than the standard 86,400 seconds, breaking the previous record of the shortest day from July 5, 2024. Which was 1.66 milliseconds shorter than the standard 24-hour day.
Scientists predicted this record. The moon sat at its furthest point from Earth’s equator, creating perfect conditions for faster rotation. Scientists worldwide confirmed the new record within hours as they watched Earth outpace their atomic clocks.
Scientists can now predict these individual fast days, but they remain confused by the overall trend. Earth has been speeding up since 2020, and no one knows why. Each record brings us closer to a problem that has never happened before.
By 2029, Earth may spin fast enough for us to subtract a second from official time. Computer systems worldwide have never been programmed to remove time, only add it. This first-ever negative leap second could cause widespread technical problems when it happens.
Breaking Records in Planetary Motion
August 5 could challenge July 9’s new record. The predicted 1.51-millisecond reduction for August 5 would fall short of July 9’s new record, but it would still rank among the shortest days ever measured.
Since 2020, Earth has spun faster than normal. That year alone produced 28 of the fastest rotations recorded since 1960. Each year since has continued this pattern, with rotations completing faster than the standard 86,400-second timeframe.
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How We Measure Such Tiny Changes
Finding these tiny changes requires extreme precision. Atomic clocks use atoms that vibrate over 9 billion times per second to track planetary rotation. Regular clocks can gain or lose minutes over time. Atomic clocks stay accurate for 300 million years without losing even one second. This lets researchers detect millisecond shifts that humans cannot feel. Our reaction time averages 200 to 300 milliseconds, making these rotation changes completely invisible to us.
Scientists Worldwide Keep Watch
Scientists around the world watch Earth’s spin using several methods. Radio telescopes track distant stars and use them as reference points to measure Earth’s position. Laser systems bounce beams off mirrors placed on satellites to gather additional data. This monitoring began in the 1970s, and today multiple systems cross-check each other’s findings. When Earth spins too fast, scientists adjust official world time to keep our clocks aligned with Earth’s actual position relative to the sun.
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The Moon’s Pull Creates the Shortest Day
The moon drives most rotation changes. On July 9, the moon was at its furthest distance from Earth’s equator. On July 22 and August 5, it will again reach this position, placing it closer to the poles. When the moon sits closer to Earth’s poles rather than its equator, Earth spins faster and days shorten.
Other forces also affect how fast the Earth spins. Melting ice and groundwater pumping move mass around the planet, slowing rotation by 1.33 milliseconds per century since 2000. Earthquakes change rotation instantly. Japan’s 2011 earthquake moved underground rock closer to Earth’s center, shortening each day by 1.8 microseconds. That’s 1.8 millionths of a second, much smaller than the millisecond changes we’re seeing recently. Even seasons matter. When northern trees grow leaves in summer, the extra weight slows Earth’s rotation slightly. Right now, the moon’s pull overpowers these slowing effects.
Why This Matters for Your Phone
Accurate timing keeps modern technology working. Your phone’s GPS calculates location by measuring how long signals take to travel from satellites. Stock trading computers execute thousands of trades per second. Internet networks coordinate signals across the globe. All need exact timing to work.
When Earth’s rotation drifts more than 0.9 seconds from official time, international organizations adjust the clocks. If Earth keeps speeding up, experts may need to subtract a second for the first time to keep everything synchronized.
Nobody Knows Why Earth’s Spin Is Accelerating
The moon’s position explains why days like July 9 are shorter than others. But the overall pattern of Earth spinning faster since 2020 remains unexplained. Scientists can predict individual short days based on lunar cycles, yet the broader acceleration trend confuses researchers because the moon’s average influence hasn’t changed.
Leonid Zotov, an Earth rotation expert, says, “The cause of this acceleration is not explained,” he notes. “Most scientists believe it is something inside the Earth. Ocean and atmospheric models don’t explain this huge acceleration.”
Earth’s rotation has slowed since the planet formed. Days lasted only 19 hours two billion years ago. Scientists study decades of rotation data to understand these competing forces. Some believe Earth has reached peak speed in this cycle and will slow again, but no one knows when.
Our Changing Planet
Each brief day adds another data point to solve the mystery of our planet’s changing rhythm. The shortest day records show Earth as an active, changing system. Atmospheric pressure, ocean currents, lunar gravity, and human activities all affect how our planet spins. While millisecond differences remain too small to sense, they provide measurable evidence of the forces that shape our world. They offer a window into the processes that make Earth active rather than static.
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