Scientists Confirm Earth’s Core Has Slowed So Much It’s Now Moving Backward—Here’s What This Could Mean

By: Georgia | Published: Jul 06, 2024

Scientists have confirmed a significant reversal in the movement of Earth’s core, observing that it has slowed to the point of moving backward. 

This surprising phenomenon marks a crucial development in geophysical research, providing new insights into the dynamic processes at Earth’s center.

Historical Discovery and Ongoing Research

The solid inner core of the Earth, discovered by Danish seismologist Inge Lehmann in 1936, rotates independently from our planet. 

A diagram showing Earth's structure with labeled layers including the crust, mantle, outer core, and inner core, drawn to scale

Source: Wikimedia Commons

Its behavior has been the subject of scientific scrutiny and debate for decades, leading to various theories about its speed and direction of rotation.


Techniques in Studying the Earth’s Core

Studying the Earth’s core relies on indirect methods due to its inaccessibility. Seismologists use seismic waves from large earthquakes to probe its movement. 

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By examining how these waves differ when passing through the core at different times, researchers can deduce changes in its position and spin.

Visual Evidence from Space

The Visible/Infrared Imager Radiometer Suite (VIIRS) on the Suomi NPP satellite provides crucial data about Earth.

An image of a satellite with large solar panels and golden foil, floating against the backdrop of space

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This data includes aspects that indirectly inform studies of the core’s dynamics through the monitoring of geophysical phenomena from space.

The Concept of Differential Core Rotation

The concept of differential rotation of Earth’s inner core was first proposed during the 1970s and 1980s. 

An image captured from space showing Earth's atmosphere and cloud patterns with a portion of a space station in the frame

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However, it wasn’t until the 1990s that this theory was substantiated with seismological evidence, according to Dr. Lauren Waszek, a senior lecturer of physical sciences at James Cook University in Australia.

Challenges in Interpreting Core Data

Interpreting data about the core’s movement presents significant challenges due to its remote location and the limited data available. 

A simple educational diagram illustrating the different layers of the Earth, including the crust, mantle, and core, with labels and a side view showing the layers beneath a section of Earth's surface

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Dr. Lauren Waszek noted, “Studies which followed over the next years and decades disagree on the rate of rotation, and also its direction with respect to the mantle.”


Recent Findings and Historical Patterns

Recent research supports a model where the core previously spun faster than the Earth itself but has since slowed, aligning with Earth’s spin before slowing further to a backward motion. 

An artistic depiction showing a cutaway view of Earth with its core and multiple layers separated and floating against a starry space background

Source: kohd1957/X

This model suggests a cyclical pattern in core dynamics spanning decades.


The Role of Earth’s Magnetic Field

The inner core, composed primarily of iron and nickel and as hot as the sun’s surface, interacts with Earth’s magnetic field. 

A scientific diagram illustrating the sun's magnetic field and its interaction with Earth, showing lines that represent magnetic forces extending from the sun to Earth

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This interaction is crucial as the core’s movement influences the magnetic field, which in turn offers protection against solar radiation.


Seismic Wave Analysis

Innovative studies using seismic waves from consistent locations over time have revealed patterns in core movement. 

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“When the core turns, that affects the arrival time of the wave,” explained Dr. John Vidale, highlighting how these findings help confirm the core’s rotation cycle.


Understanding the Core’s Rotation Cycle

The research indicates that the core’s rotation follows a 70-year cycle, involving periods of speeding up and slowing down. 

Long exposure photograph capturing circular star trails centered around Polaris, the North Star, showing the Earth's rotation

Source: Fred Moon/Unsplash

This cyclical behavior is crucial for understanding the temporal dynamics of Earth’s deepest layers.


Implications of Core Activity

Although changes in the core’s spin are subtle, they have a measurable impact on Earth’s rotation and consequently the length of a day. 

Highly detailed and colorful artistic rendering showing a cross-sectional view of Earth’s interior layers including the core, mantle, and crust

Source: EndTimeHeadline/X

However, these changes amount to only milliseconds, often imperceptible in daily life but significant over geological time scales.


Future Research Directions

The continued study of the inner core is vital for understanding Earth’s geophysical behavior. 

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Dr. Lauren Waszek emphasized the need for more data and improved interdisciplinary tools to explore these deep Earth processes further, indicating that the debate over core dynamics is far from settled.