What happens if Earth stops rotating?
Etan Meyer
Boca Raton, FL
I will assume you’re referring to what would happen if Earth stopped rotating all at once, without any gradual reduction in velocity. In that event, most things on Earth would be almost immediately destroyed.
To illustrate, let’s say you’re riding in a car. If the car is traveling at 70 mph (112.7 km/h), your body will also be traveling at 70 mph. If the car suddenly stops, your body initially continues to move at 70 mph — which is why a seatbelt is necessary to prevent you from moving rapidly toward the windshield. We don’t feel motion when we travel at a constant velocity. We do feel motion when our vessel experiences a sharp acceleration or deceleration.
Now, most of Earth is moving much more quickly than a car. A point along the equator moves at approximately 1,037 mph (1,668 km/h). This tangential velocity decreases with increasing distance from the equator; for instance, Earth’s speed in New York City is about 794 mph (1,277.8 km/h), and at the poles, it is reduced to zero. (You can figure out this speed V in mph at any latitude with the formula V = 1,036cos(latitude).) If Earth stopped spinning in an instant, all the water, air, and structures on Earth would still be moving at speeds corresponding to their latitudes.
So on the equator, you’d experience wind speeds in excess of 1,000 mph, a velocity nearly five times greater in speed (and 25 times greater in force) than the strongest wind speed ever recorded on Earth’s surface to date. Anybody who’s ventured outside to experience a 75-mph wind gust can begin to appreciate the power of 1,000-mph winds. Almost all structures would collapse at once, and everyone and everything not firmly anchored to the ground would be violently displaced. Even the ground itself would buckle, split, and tear in response to a sudden stop.
Not to mention the oceans: Remember that the water in the oceans will also be moving along Earth’s surface at a speed corresponding to its latitude. If Earth were to stop turning suddenly, that water would continue to move at a rapid velocity, inundating coastal and possibly even inner regions with a deluge of displaced ocean water. The ocean surface might yield to our touch, but anyone who has waded in a swift current will know water’s immense power.
We would experience other effects as well, such as the distortion of Earth’s shape. We often describe our planet as spherical, but Earth is actually an oblate spheroid (the distance across the equator is slightly greater than the distance separating the poles). This oblateness results from the centrifugal force of the planet’s rotation. Without that centrifugal force, the planet would quickly become more spherical, causing the ocean waters to migrate rapidly toward the poles.
Oceans drowning large swaths of the continents; winds far more intense than humans could withstand; Earth’s surface cracking violently open; volcanoes erupting worldwide and spewing megatons of ash, fire, and debris into the atmosphere — in short, the end of the world could be achieved merely by stopping its spin.
Incidentally, after the introduction of atomic clocks, scientists became aware that Earth’s rotation rate fluctuated, both speeding up and slowing down. Over time, the general trend was toward diminishing — but the decrease in speed was very gradual, only fractions of milliseconds per year. Beyond the occasional addition of “leap seconds” to compensate, ramifications over the short term were negligible. (Between 1972 and 2020, 28 leap seconds were added to atomic time.) However, recent measurements have shown a trend toward an increased rate of rotation, suggesting a leap second may actually need to be subtracted in 2029. Tidal forces, seismic events, climate change, and many other factors can affect Earth’s rotation rate, so even though fluctuations will continue, you can rest assured that Earth will never actually stop rotating.
Edward Herrick-Gleason
Astronomy Educator, St. John’s, Newfoundland and Labrador
