Could the rotation of Earth ever stop?

The alternation of day and night may seem natural, yet our planet’s motion is constantly changing. But what would happen if the familiar rhythm of the rotation of Earth were suddenly disrupted? Will the Earth keep spinning forever, or could it one day come to a halt?

For centuries, the rotation of Earth has formed the basis of human timekeeping, yet few people consider that this motion is not constant. Our days are slowly getting longer, and although the change is barely noticeable at first, on a cosmic timescale it is a significant process. But could there come a moment when the Earth completely stops?

The rotation of Earth and its consequences

The Earth currently takes about 24 hours to complete one rotation around its axis. This has not always been the case, however. As an article by IFLScience points out, the planet rotated faster in ancient times. Scientific estimates suggest that around 600 million years ago, a day on Earth lasted only about 21 hours, meaning our planet’s rotation has slowed down considerably since then.

The slowing of the rotation of Earth can still be measured today. Research shows that the length of a day increases by an average of 1–2 milliseconds per century. Although this may seem negligible at first, over long periods it can lead to significant changes. According to NASA, between 2000 and 2018 the increase in day length reached 1.33 milliseconds due to the movement of ice and groundwater — a faster rate than in the previous hundred years.

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What processes slow down the rotation?

The most important factor slowing the rotation of Earth is the influence of the Moon. The Moon’s gravity is responsible for tidal forces, which create a form of friction that gradually slows the planet’s spin.

This process does not only affect the Earth, but also the Moon’s orbit. Our natural satellite is moving away from the planet by about 4 centimetres per year. The energy driving this recession comes from the movement of the oceans. As a result, the rotation of Earth continues to slow while the Moon drifts ever further away from us.

Climate change also affects the Earth’s rotation. The melting of ice and the redistribution of underground water reserves alter the planet’s mass distribution, which in turn influences rotational speed. According to NASA, if the situation does not change, the increase in day length could reach as much as 2.62 milliseconds per century, surpassing the effect of tidal forces linked to the Moon.

What would happen if the Earth suddenly stopped?

Although it is extremely unlikely that the rotation of Earth could cease from one moment to the next, it is worth considering the idea. Such an event would almost certainly have catastrophic consequences. Everything on the surface — water, rocks, buildings — would be hurled eastwards by the enormous momentum at speeds exceeding 1,600 km/h.

This would cause massive destruction, and debris would be thrown into the atmosphere and even into space. Falling rock fragments would continuously bombard the planet, causing the Earth’s crust to melt and forming a so-called “rock ocean”. Fortunately, the Earth cannot stop rotating this abruptly unless an enormous cosmic collision were to occur.

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The threat of tidal locking

If the relationship between the Earth and the Moon remained unchanged, our planet would eventually become tidally locked to the Moon over an extremely long period of time. This would mean that one side of the Earth would always face the Moon, while the other side would never see it. In this state, the length of days and nights would match the Moon’s orbital period.

However, this scenario would only occur in around 50 billion years — assuming the Sun does not swallow our planet first. Astronomical calculations indicate that the Sun will become a red giant in about 7.6 billion years, during which the Earth will most likely be destroyed.