Earth’s Rotation Is Slowing Down. And the Most Surprising Thing Is That It's Been Doing So for Millions of Years

Cosmology is one of the most challenging scientific disciplines. Astrophysicists have significantly advanced our understanding of the universe in recent decades. However, speaking transparently and honestly, humans are still entirely ignorant in this area. We don’t even understand the cosmological behavior of our planet very well. This is the conclusion of a study published in the Proceedings of the National Academy of Sciences by several geoscientists from different research institutions.

​​On this occasion, it’s worth starting with their conclusion, which is the most striking: The rotation of our planet is slowing down. Moreover, it's been doing so for millions of years. It seems reasonable to assume that the Earth’s rotational speed is constant, given its continuous gravitational interaction with the objects in its environment and the almost total absence of variation in its mass. But it’s not constant. And the explanation for this behavior isn’t simple at all.

The Slowdown of Earth’s Rotation Follows a Staggered Pattern

This isn’t the first study to show that our planet is slowing down, but it’s the first to measure the extent of the slowdown consistently. To reach this conclusion, the scientists studied sediment samples dating back at least 650 million years. More interestingly, however, they set out to analyze eight sets of geological data from 280 to 650 million years ago.

The first surprise of their research is that the slowing of the Earth’s rotation hasn’t been smooth. And the second is that it hasn’t been constant. This means the rate at which the planet’s rotation slows varies. In fact, according to the study's authors, the slowdown follows a stepwise pattern. In practice, this behavior suggests that periods of very pronounced slowing alternate with others where the rotation rate is stable.

The staggered pattern that describes this behavior is unexpected and challenging to explain. Nevertheless, the scientists have observed that one of the stable periods occurred during the enormous diversification of life in the Cambrian period and the other during the largest mass extinction known to date. The second happened at the end of the Permian period, which triggered the disappearance of approximately 96% of marine and 70% of terrestrial species. The devastation on our planet was so great that scientists refer to this period as the Great Dying.

The complexity of the phenomenon in question hasn’t prevented these researchers from concluding that tidal dissipation has caused the slowing of Earth's rotation in modern times. This mechanism results from the dissipation of orbital and rotational energy caused by the warming of the surface waters of the oceans, the behavior of the planet’s inner layers, or the Moon’s dynamics.

The Moon stretches and compresses as it moves away from and toward the Earth, causing a phenomenon known as “tidal heating.” Scientists are now trying to establish links between changes in the Earth’s rotation and major environmental events.

This article was written by Juan Carlos López and originally published in Spanish on Xataka.

Image | SpaceX

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