What If Earth Stopped Spinning?

A sudden stop would be catastrophic. A slow stop would give us six months of daylight, six months of night, and oceans that drain toward the poles. Here is what would happen.

Earth rotates once a day, which means a point on the equator moves at about 1,670 km/h. We do not feel it because everything — air, oceans, us — moves along with the ground. That is what makes the question interesting.

If it stopped suddenly

This cannot actually happen — no known natural process could stop a planet in an instant — but as a thought experiment it shows how much is moving. The solid Earth would halt, while the atmosphere and oceans kept going. Near the equator, winds would sweep across the surface faster than the strongest tornadoes, and oceans would surge over the land. Anything not attached to bedrock would keep moving too.

If it slowed down gradually

The more interesting version is a slow stop over a long time.

One day per year

If Earth stopped rotating relative to the stars, it would still orbit the Sun. Each place would get about six months of daylight followed by six months of night. The day side would bake and the night side would freeze, and winds would constantly carry heat from one to the other.

The oceans move

Earth's spin makes it bulge at the equator — the equator is about 21 km farther from the centre than the poles. The oceans follow that bulge. If the spin stopped, the solid Earth would slowly relax towards a rounder shape, but the water would respond faster: it would flow towards the poles, forming two large polar oceans with one giant continent wrapped around the equator.

Weather changes

Hurricanes and the swirling patterns of weather systems depend on Earth's rotation through the Coriolis effect. Without spin, global weather would be organised mainly by the difference between the day side and the night side.

The magnetic field

Earth's rotation helps organise the flow of liquid iron that generates the magnetic field. A non-rotating Earth might have a much weaker or less organised field, though scientists cannot say exactly how it would behave.

Earth is actually slowing down

Tidal friction from the Moon is gradually slowing Earth's rotation. The day gets longer by roughly 2 milliseconds per century. Hundreds of millions of years ago, a day was only about 22 hours. Earth will not stop spinning before the Sun changes — but the slowdown is real.

Real planets that barely spin

Venus rotates once every 243 Earth days, and many planets around red dwarfs are probably tidally locked, always showing the same face to their star.