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New research has confirmed that our planet’s core has been rotating unusually slowly over the past 14 years. If this mysterious trend continues, it will likely lengthen Earth’s days, although the effects will likely be imperceptible to us.
Earth’s inner core is a roughly moon-sized chunk of solid iron and nickel located more than 3,000 miles (4,800 kilometers) beneath our feet. It is surrounded by the outer core – an extremely hot layer of molten minerals similar to that of the inner core – which is surrounded by a much solider sea of molten rock, known as the mantle, and the crust. Although the entire planet rotates, the inner core can rotate at a slightly different speed than the mantle and crust due to the viscosity of the outer core.
Since scientists began mapping the Earth Inner layers With detailed records of seismic activity from about 40 years ago, the inner core is rotating slightly faster than the mantle and crust. But in a new study published on June 12 in the journal natureThe researchers found that since 2010, the inner core has been slowing down and is now rotating slightly slower than our planet’s outer layers.
“When I first saw the seismograms that hinted at this change, I was puzzled.” John VidalUniversity of Southern California seismologist Dornsife said in A statement. “But when we found twenty other observations pointing to the same pattern, the conclusion was inevitable.”
If the rotation of the inner core continues to slow down, its gravity could eventually cause the outer layers of our planet to rotate a little slower, changing… All our days The researchers wrote.
However, Vidal said any potential change would be on the order of a millisecond, which would be “very difficult to notice.” As a result, we likely won’t have to change our clocks or calendars to account for this difference, especially if it’s just a temporary change.
Related: Discovering a “new hidden world” in the Earth’s inner core
This is not the first time scientists have suggested that the Earth’s inner core is slowing down. This phenomenon, known as “regression,” has been discussed for about a decade, but has been very difficult to prove.
In the new study, researchers analyzed data from more than 100 recurrent earthquakes — seismic events that occur repeatedly at the same location — along the Tectonic plates Boundaries in the South Sandwich Islands in the South Atlantic Ocean between 1991 and 2023.
Each earthquake allowed scientists to map the location of the core relative to the mantle, and by comparing these measurements, the team was able to see how the rotation rate of the inner core changed over time.
Vidal said the new study is the “most convincing” evidence to date of a decline.
It is currently unclear why the inner core is retracting, but it is likely caused by either “the churning of the outer core of liquid iron that surrounds it” or “gravitational forces of gravity from dense regions of the overlying rocky mantle,” the researchers wrote.
It is also unclear how frequent the decline will be. It is possible that the rotation of the inner core is constantly accelerating and decelerating, but these changes are likely to occur over decades or more. Therefore, longer data sets are needed to infer anything about long-term trends.
The inner core remains one of Earth’s most mysterious hidden layers. But in recent years, new techniques have allowed researchers to learn more about the inner core, including what it is A little unbalancedThis is it Softer than expectedit is likely It oscillates off the Earth’s axis And it contains Separate deeper core.
The study authors will continue to analyze seismic data to learn more about the core of our planet and how it changes over time.
“The dance of the inner heart may be more vibrant than we know,” Vidal said.
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