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Date: January 23, 2023 at 09:44:48
From: ryan, [DNS_Address]
Subject: Earth's inner core seems to be slowing its spin |
URL: https://www.sfgate.com/news/article/Earth-s-inner-core-seems-to-be-slowing-its-spin-17735947.php |
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Earth's inner core seems to be slowing its spin
Carolyn Y. Johnson, The Washington Post
Jan. 23, 2023
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In the mid-1990s scientists found evidence that Earth's inner core, a superheated ball of iron slightly smaller than the moon, was spinning at its own pace, just a bit faster than the rest of the planet. Now a study published in Nature Geoscience suggests that around 2009, the core slowed its rotation to whirl in sync with the surface for a time - and is now lagging behind it.
The provocative findings come after years of research and deep scientific disagreements about the core and how it influences some of the most fundamental aspects of our planet, including the length of a day and fluctuations in Earth's magnetic field.
Three thousand miles below the surface, a scorching hot ball of solid iron floats inside a liquid outer core. Geologists believe that the energy released by the inner core causes the liquid in the outer core to move, generating electrical currents that in turn spawn a magnetic field surrounding the planet. This magnetic shielding protects organisms on the surface from the most damaging cosmic radiation.
Don't panic. The core's slowing down isn't the beginning of the end times. The same thing appears to have happened in the late 1960s and early 1970s, and the study authors at Peking University in China suggest it may represent a 70-year cycle of the core's spin speeding up and slowing down.
But while other experts praised the rigor of the analysis, the study will sharpen, not settle, the fierce scientific debate about what the mysterious metal sphere at the center of the Earth is up to.
"It's only contentious because we can't figure it out," said John Vidale, a geophysicist at the University of Southern California. "It's probably benign, but we don't want to have things we don't understand deep in the Earth."
The new study was led by Xiaodong Song, a geoscientist at Peking University whose work in 1996 first brought forward the evidence that the core was doing its own thing. Buried beneath the mantle and the crust, the core is too deep to visualize directly, but scientists can use seismic waves triggered by earthquakes to infer what's happening in the planet's innards. Seismic waves travel at different speeds depending on the density and temperature of the rock, so they act as a kind of X-ray for Earth.
The study examined seismic waves that traveled from the sites of earthquakes to sensors on the flip side of the planet, passing through the core on the way. By comparing waves from similar earthquakes that struck the same spot over the years, the scientists were able to search for and analyze time lags and perturbations in the waves that gave them indirect information about the core - or as some scientists call it, the planet within our planet.
"The inner core is the deepest layer of Earth, and its relative rotation is one of the most intriguing and challenging problems in deep-earth science," Song said in an email.
The behavior of the core may be linked to minute changes in the length of a day, though the precise details are a matter of debate. The length of a day has been growing by milliseconds over centuries because of other forces, including the moon's pull on Earth. But ultra-precise atomic clocks have measured mysterious fluctuations.
These variations may line up with changes in the core's rotation, Song and colleagues argue. The new paper finds that, when they remove predictable fluctuations in the length of a day due to the moon's tidal forces, there are changes that appear to track with the 70-year oscillations in the inner core's rotation.
Paul Richards, a seismologist at the Lamont-Doherty Earth Observatory at Columbia University, worked with Song to put forward the initial evidence that the core was spinning faster than the rest of the planet.
"Most of us assumed that the inner core rotated at a steady rate that was slightly different from the Earth," Richards said. "The evidence accumulates, and this paper shows that the evidence for [faster] rotation is strong before about 2009, and basically dies off in subsequent years."
Still, he cautioned that things get speculative quickly when trying to understand the influence of the core on other phenomena. That's because the behavior of the core itself is still a contested question - with simplistic assumptions increasingly refined over the years.
For example, there are lines of evidence to support other ideas about how Earth's core is behaving. USC's Vidale has studied seismic waves generated by nuclear explosions, and he favors a shorter, six-year oscillation for the core's rate of rotation.
Lianxing Wen, a seismologist at Stony Brook University, rejects altogether the idea that the core is rotating independently. He argues that changes over time to the surface of the inner core are a more plausible explanation for the seismic data.
"This study misinterprets the seismic signals that are caused by episodic changes of the Earth's inner core surface," Wen said in an email. He added that the idea the inner core is rotating independent of the surface "provides an inconsistent explanation to the seismic data even if we assume it is true."
What geoscientists do agree on is that as more data have accrued, many of the initial ideas about the core's behavior have grown more complicated.
"Ultimately I don't think that things being complicated is a problem in geoscience," Elizabeth Day, a geophysicist at Imperial College London, said in an email. "We know the surface of our planet is complex . . . so it is reasonable to assume the deep interior is also complicated! To definitely say how the inner core is rotating relative to the outer layers of the planet, we will need to keep collecting as much data as we can."
The stakes of this scientific debate are high in part because the core is a mystery that lurks, unsolved, so tantalizingly close to home.
"This is not something that's going to affect the price of potatoes tomorrow," Richards said. But the debate speaks to more profound questions about Earth's formation and how its inner layers support life on its surface, something that may aid studies of habitability on rocky planets circling other stars.
"When you think . . . what our planet consists of and what its history is," Richards said, "a deep understanding of the inner core gets you into 'How did all these divisions of planet Earth evolve?'"
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[7241] [7243] [7244] [7245] |
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Date: January 23, 2023 at 23:26:39
From: ryan, [DNS_Address]
Subject: Re: Earth's inner core seems to be slowing its spin |
URL: https://thehill.com/homenews/nexstar_media_wire/3827244-earths-inner-core-may-have-paused-its-rotation-and-reversed-new-study-suggests/ |
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Earth’s inner core may have ‘paused’ its rotation and reversed, new study suggests
by Addy Bink - 01/23/23 8:07 PM ET
(NEXSTAR) – Deep in the center of the Earth is the inner core, which spans roughly 746 miles and is composed of primarily pure, solid iron, NASA explains. Though we’ve long believed – and research has shown – that the inner core rotates, a new study suggests it may have “paused” its spin and could even have reversed.
The liquid outer core that surrounds the inner core causes Earth’s magnetic field. According to NASA, as the molten iron and nickel in the outer core move, they create electrical currents that result in a magnetic field. The outer core also allows the inner core to spin on its own, Nature explains.
Though scientists can’t track the core directly, they can analyze seismic waves caused by earthquakes – and Cold War-era nuclear weapon tests – as they reach the core. That’s what study co-authors Yi Yang and Xiaodong Song, seismologists at Peking University in Beijing, did for their new research, which was published in the Nature Geoscience journal on Monday.
Based on their analysis of seismic waves caused by similar earthquakes dating back to the 1960s, Yang and Song said they found that the inner core’s rotation seems to have “paused” between 2009 and 2020 and could even be reversing “by a small amount.”
Sounds concerning, right? Don’t be alarmed – this likely isn’t the first time our inner core has come to a halt. Instead, they believe the change is “associated with a gradual turning-back of the inner core as part of an approximately seven-decade oscillation.”
According to Yang and Song, results from their study also suggest “another overturn or a slowdown of the rotation around the early 1970s.”
The seismologists said their findings – changes in how fast seismic waves traveled through the inner core – coincide “with changes in several other geophysical observations, especially the length of day and magnetic field,” which are both areas that are impacted by the inner core’s movement, research has shown.
While the changes are “valid,” what Yang and Song found may not be exactly what’s happening in the depths of our planet. John Vidale, a professor of earth sciences at the University of Southern California that wasn’t involved in the study, noted “several competing ideas” about the Earth’s core to The Wall Street Journal.
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This includes theories that the inner core reverses its rotation more frequently than the 70 years Yang and Song determined and that it stopped rotating in the early 2000s.
“No matter which model you like, there’s some data that disagrees with it,” Vidale told The New York Times.
Vidale recently co-authored a study that showed the inner core changed its spin between 1969 and 1974, and that it seems to oscillate “a couple of kilometers every six years.”
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Date: January 25, 2023 at 04:42:47
From: Eve, [DNS_Address]
Subject: Re: Earth's inner core seems to be slowing its spin |
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Thanks. I don't visit this board often and saw an article
on this and posted it on earth watchers...I see now your
post here. I was thinking,...hmm which board? doh on me.
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Date: January 25, 2023 at 09:49:44
From: ryan, [DNS_Address]
Subject: Re: Earth's inner core seems to be slowing its spin |
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earthwatchers is fine for it too...
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Date: January 25, 2023 at 10:07:09
From: Eve, [DNS_Address]
Subject: Re: Earth's inner core seems to be slowing its spin |
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Responses:
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