Scientists Explain the Real-World Consequences if Earth's Rotation Accelerated

Scientists have recorded tiny, millisecond-scale changes in the length of Earth’s day in recent years and say researchers are examining several natural drivers, from atmosphere and ocean circulation to mass redistribution in the planet’s core and melting ice. While authors of a recent novel imagine an extreme, civilization-shattering acceleration of rotation, geophysicists and other experts say such a scenario would require a major transfer of angular momentum and is not supported by observed physics. They also detail the physical effects that would arise if the planet’s spin did increase substantially.

Atomic clocks and global observational systems show that the length of a solar day is not perfectly constant. The fastest day recorded in recent data occurred on July 5, 2024, when Earth completed a rotation about 1.66 milliseconds shorter than the nominal 24‑hour period. Other days this year — July 9, July 22 and Aug. 5 — were between about 1.3 and 1.51 milliseconds shorter than 86,400 seconds, the standard count used to define a 24‑hour day. Scientists say those small variations are expected and have been tracked more precisely only since high‑precision atomic timekeeping became widely available in the 1970s.

Researchers are considering several natural processes that can alter rotation by tiny amounts. Seasonal and large‑scale shifts in atmospheric circulation, changing ocean currents and accelerated melting of glaciers can alter the distribution of mass on and within the planet and thus the moment of inertia, producing slight speedups or slowdowns. Motion in the molten outer core and changes in the geomagnetic field are additional possible contributors, experts say. "Scientists are looking at the moon's orbit, core activity, ocean flow and wind patterns together to figure out what's going on," one researcher told reporters.

In public commentary prompted by a new novel titled Circular Motion, which imagines days shrinking from 24 hours down to two hours, some scientists have been asked to assess the real consequences of a much faster rotation. Geophysicist Duncan Agnew at the University of California, San Diego, said the largest near‑term changes would appear in the oceans: a faster spin increases the centrifugal effect at and near the equator, causing water to bulge outward. That redistribution of mass would raise sea levels around the equator and make polar seas shallower, increasing the risk of regional flooding and changing tidal behavior.

"Change [rotation] by 10 percent and the tides in some places would get larger and in others smaller," Agnew said. He added that sliding and interacting of tectonic plates could accelerate under altered rotational and centrifugal stresses, increasing geological strain and the potential for more frequent or larger earthquakes.

An increase in rotation rate would also amplify the Coriolis force, which influences atmospheric circulation and the spin of storms. NASA‑affiliated astronomer Sten Odenwald warned that hurricanes and cyclones would likely spin faster and carry more energy if the Coriolis effect intensified, producing more extreme wind fields and altered storm tracks. Faster rotation would shorten the length of daylight and night, with implications for biological circadian rhythms and human activities. "Humans have a circadian rhythm closely attuned to the 24‑hour day," scientists note; abrupt shifts in day length would pose physiological and societal challenges.

Technological systems could also be affected. Satellites are placed into orbit and phased with respect to Earth's rotation; a sustained change in spin rate would require adjustments to many satellite constellations to preserve communications, navigation and remote sensing services. Timing systems and legal definitions of civil time would require recalibration if changes became large enough to matter for everyday scheduling.

Despite those plausible consequences of a materially faster rotation, multiple experts emphasized that the extreme, progressive acceleration depicted in the novel — in which days rapidly shorten to hours — is not consistent with known planetary dynamics. "This cannot happen and nothing like it has ever been observed for any planet or star," Agnew said in comments reported in the media. He noted that, over geologic time, Earth has generally been slowing due to tidal friction with the Moon, not speeding up.

Judah Levine, a fellow at the U.S. National Institute of Standards and Technology, noted that any sustained speedup of Earth's rotation would have to be accompanied by an exchange of angular momentum elsewhere in the Earth–Moon system or by a rare and massive external event. "If the speed‑up had to be accompanied by something else losing angular momentum, maybe the orbit of the Moon," Levine said. Were the Moon to transfer significant angular momentum to Earth, its orbit would change and tidal effects would grow stronger and more frequent.

Scientists stress that the small millisecond variations observed in recent years do not indicate a runaway acceleration. Earth’s rotation has natural fluctuations on short time scales and a long‑term trend of gradual slowing; for instance, paleontological and geological evidence suggests that a billion years ago the length of a day may have been shorter, perhaps around 19 hours, and in the planet’s earliest history rotation was much faster before the current Earth–Moon configuration was established. But the magnitudes of short‑term changes recorded by modern instruments — a few milliseconds — are tiny compared with the changes required to produce major geophysical reconfiguration.

Researchers continue to study the causes of the observed millisecond variations, comparing atomic‑clock timekeeping with astronomical measurements and models of mass redistribution within the Earth system. Understanding the interplay of atmosphere, ocean, cryosphere and the deep interior remains an active area of research because even small changes in rotation can provide insight into internal and surface processes.

In the meantime, experts say, dramatic fictional scenarios of rapid planetary spin‑up make useful premises for storytelling but should not be read as plausible near‑term outcomes grounded in current geophysics. Real‑world concerns remain focused on understanding and adapting to the small but measurable fluctuations that modern instruments can now detect, and on the physical mechanisms that produce those changes rather than on catastrophic alterations that would violate conservation of angular momentum without an extraordinary cause.