While tracking seismic waves as they travel from the Earth’s crust to its core, geophysicist John Vidal noticed something surprising.
The Earth’s center, a solid sphere of iron and nickel floating in an ocean of molten rock, appears to be slowing down compared to the Earth’s own motion. The inner core has slowed down so much that it is essentially rotating in the opposite direction.
The findings of Vidale and Wei Wang’s study are: Chinese Academy of Sciencesrecently published in the journal Naturepresents the most compelling evidence yet that the core appears to operate with a mind of its own.
“It could be going back and forth, or it could be a random walk,” Bedale said. “It’s going one way for a while, then it goes back another way. Who knows what it’ll do next?”
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The changes happening 3,000 miles below the Earth’s surface aren’t likely to have a noticeable effect on life on the planet’s surface, at least for now, Vidal said.
“From what we’ve seen, there’s essentially no impact on humans,” said Vidale, chair of the Department of Earth Sciences in the Doon Seif College of Arts and Sciences at USC. “This is basically part of understanding the evolution of the Earth. What we want to know more about is what are the forces that are driving the inner core.”
Scientists first had a hunch that the inner core was moving in the 1990s, he said, but it took years to back up that theory with solid evidence, mainly because of the difficulty of studying such a remote, inaccessible mass, suspended in a hellish ocean of liquid iron at 8,000 to 10,000 degrees.
Instead, Vidale, who served as director of the University of Southern California’s Southern California Seismological Center from 2017 to 2018, peered closely at the planet by tracking seismic waves from an earthquake off the southern tip of South America. As the waves passed through the Earth’s center, they were recorded on the other side of the planet by 400 seismometers in Alaska and northern Canada. The sensors were the same kind used to measure ground vibrations during nuclear testing.
He compared these precise measurements with previously recorded seismic signals to see where they matched up, and found that the rotation has been slowing down since 2010. Before that, the core was spinning faster.
Bidale said the discovery adds to the mystique of one of the most mysterious parts of the Earth. Literature and folklore about the Earth’s core have filled in the gaps in knowledge with a variety of fantastical ideas.
“I’m no philosopher, but we’ve all had nightmares about what goes on under the Earth,” says Vidale. “Only 200 years ago, people thought the Earth was hollow and inhabited. It’s so bizarre. It’s like Jupiter, but it’s under our feet.”
In Jules Verne’s 1864 sci-fi classic Journey to the Center of the Earth, a German professor, his nephew and a guide descend to Earth through an Icelandic volcano, encountering caves, an underground ocean, living dinosaurs, strange sea creatures and even a giant prehistoric mastodon along the way before being spat out of a volcano off the coast of Sicily.
In the 2003 disaster movie The Core, the Earth’s center has stopped rotating, the magnetic field surrounding the planet has been damaged, violent thunderstorms have destroyed Rome, and “invisible microwaves” have melted the Golden Gate Bridge. A team of brilliant scientists drills into the Earth’s layers and activates the Earth’s center with a nuclear bomb.
In the real world, even if someone had a vehicle capable of tunneling to the core, no human could withstand the unimaginable heat and bone-shattering pressures, Vidar said.
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While it’s true that the outer core generates the electric currents that maintain the planet’s magnetic field, changes in the inner core, which is the size of Texas, are too small to have any effect, Vidale said.
The reality of the planet’s underground is less fantastical than depicted in novels and Hollywood movies, but it’s still intriguing to people like Vidar, whose job it is to counter speculation with fact.
What’s becoming increasingly clear is that the inner core is affected in many ways by activity in the layers of the Earth that surround it.
“The way it works is that the outer core circulates and creates a magnetic field that pulls the inner core back and forth,” Vidar said.
Another element of the never-ending tug-of-war inside the planet is the planet’s lower mantle, where a unique mix of hard and less dense material creates magnetic forces, Vidale said.
“We think the outer core is churning the inner core, but the mantle is trying to keep it aligned, and that could be the reason for the vibrations,” he said.
The latest discoveries about the inner core have sparked fierce disagreement among the world’s top geoscientists, pitting a variety of theories of differing plausibility, Vidal said. Some don’t believe the core rotates at all, while others say surface forces like earthquakes can temporarily alter its rotation.
Over the phone, Vidale reads out a review by an Australian scientist who was highly skeptical of Vidale’s recent findings: The Australian asserts that the analysis will lead to “the decline of seismology as a credible branch of science and the downfall of seismologists as credible researchers.”
“I think he’s just frustrated. He knows he lost,” Vidale gently teased his companion.
“It’s exciting because the nucleus is pretty big, it’s moving in measurable amounts, and it’s full of mysteries,” Vidal said. “We’re making progress, we’re seeing more, we’re discussing it with people around the world, we’re getting more data… Our paper is largely of the community.”
This story was originally Los Angeles Times.
