Earth’s Spin Is Slowing Down, What Does It Mean?

By Kelly Bjornstad

The Earth’s spin is slowing down and experts say it’s not the beginning of the end, but rather something that’s been happening for billions of years. Sid Perkins from writes “Overall, Earth’s spin has slowed by about 6 hours in the past 2740 years, the team reports today in the Proceedings of the Royal Society A. That sounds like a lot, but it works out to the duration of a 24-hour day being lengthened by about 1.78 milliseconds over the course of a century.” With the slowing of earth’s rotation, the days get ever so slightly longer; a matter of milliseconds. This new data also allows scientists to better understand the movements of matter deep below Earth’s surface. For example, Earth’s molten hot, liquid iron level surrounding the core (which gives Earth an electromagnetic field). 

 Leslie Morrison, an astronomer, now retired, from the Royal Observatory Greenwich in London talks about these variations in spin rate, saying “These glitches are apparent from astronomical observations of occultations of stars by the moon—miniature eclipses that occur when the moon passes in front of the distant star. The variations stem from momentum shifts between Earth’s liquid outer core and the solid mantle that overlies it,”

This slowing can be mainly attributed to the moon and its influence on Earth’s tides. The sea’s constant, intense break on Earth’s landmasses causes the Earth to lose momentum as it spins. Global warming has only fed into this effect, as large sheets of ice continue to melt and add to the oceans force as it meets with shores across the planet. Morrison builds on this idea, explaining previous variations in which the Earth rate rotation speed was increasing, compared to the current decrease we’re experiencing. Saying “…the crust is springing upward at high latitudes, at lower latitudes the planet is shrinking inward. Like an ice skater bringing her arms inward to spin faster, that overall shift of mass is speeding up Earth’s rotation.”

Actionnews5 breaks down this slight shift, explaining “For billions of years, the moon has been ever so gently tugging at the Earth and slowing down its rotation.” Which only affirms the idea mentioned previously as the moon has great influence over our tides. Some researchers have taken it upon themselves to study the length of our days some 1.4 billion years ago, estimating that our days used to be just 18.7 hours long. Actionnews5 wrote “ At that time, the moon was likely some 27,000 miles closer to Earth than it is now, they say.”

A slowing in Earth’s rotation speed may be concerning, but experts explain that actually, the variation has caused an increase in Earth’s oxygenation. Meaning, there’s more oxygen on Earth. The great Oxidation event on Earth billions of years ago allowed cyanobacteria to be so plentiful on Earth that the amount of oxygen took a sharp increase. Without this, it’s likely that humans would never have been able to sustain life here on this planet. Sciencealert notes  “…the team found that lengthening days were linked to the increase in Earth’s oxygen – not just the Great Oxidation Event, but another, second atmospheric oxygenation called the Neoproterozoic Oxygenation Event around 550 to 800 million years ago.” And adds “It’s pretty exciting. This way we link the dance of the molecules in the microbial mat to the dance of our planet and its Moon.”

As the Earth’s spin continues to change, it’s important not to panic! This slowing isn’t a cause of worry, but rather bringing us new evidence of microbial connections and environmental changes. 

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