Study: Earth's Inner Core May Be Changing Speed
2023-01-27
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1A recent study suggests that the rate at which the Earth's center is turning is slowing down compared to the outer parts of the planet.
2Earth scientists, or geologists, say that the center or core of the Earth can rotate, or turn, at a different rate than the outer areas.
3The latest research appeared in the scientific publication Nature Geoscience.
4The writers of the research are Xiaodong Song and Yi Yang of China's Peking University in Beijing.
5They used information about seismic waves from earthquakes to study the core.
6Earth's inner core is a ball of hot iron that is a little smaller than the Moon.
7Because it floats in the liquid metal of the outer core, it can spin at a different speed than the rest of the planet.
8In the 1930s, scientists discovered the Earth's core by studying changes in the speed of seismic waves as they travelled through the planet.
9The changes in speed showed that the core was a solid center made mostly of iron.
10The new research by Song and Yang studied what they called "repeated seismic waves from the early 1990s."
11They looked for changes in the amount of time seismic waves take to travel over the same paths inside the Earth.
12The scientists suggest changes in the spin of Earth's core can explain the changes in travel times.
13"We believe the inner core rotates, relative to the Earth's surface, back and forth, like a swing," they told The French news agency AFP.
14They added that its relative rotation changes about once every 35 years.
15They also said these changes correspond with very small changes in "length of day"-the exact amount of time it takes for Earth to rotate on its axis.
16In June 2022, John Vidale and Wei Wang, Earth scientists at the University of Southern California (USC), published a study in Science Advances.
17They reported that between 1969 and 1971 the core rotated more slowly than the outer layers.
18They also said that after 1971, the core rotated faster than the outer layers.
19In their study, Wang and Vidale used data on seismic waves from nuclear test explosions.
20Earth scientists say the Earth's core is difficult to understand and study.
21They disagree about how much, and how often, the spin might change.
22Some scientists argue that the speed of the spin does not change at all.
23They say the changes in seismic waves are caused by changes on the surface of the inner core instead of differences in how fast the core is spinning.
24Hrvoje Tkalcic is a geophysicist at the Australian National University.
25He thinks scientists will disagree about the latest research.
26He compared seismologists, who study earthquakes and seismic waves, to doctors "who study the internal organs of patients' bodies using imperfect or limited equipment."
27He added: "Our image of the inner Earth is still blurry."
28Song and Yang said scientists need years of seismic data to answer questions about Earth's core.
29Vidale of USC said, "Something's happening and I think we're going to figure it out. But it may take a decade."
30I'm Andrew Smith.
1A recent study suggests that the rate at which the Earth's center is turning is slowing down compared to the outer parts of the planet. 2Earth scientists, or geologists, say that the center or core of the Earth can rotate, or turn, at a different rate than the outer areas. 3The latest research appeared in the scientific publication Nature Geoscience. 4The writers of the research are Xiaodong Song and Yi Yang of China's Peking University in Beijing. They used information about seismic waves from earthquakes to study the core. 5Earth's inner core is a ball of hot iron that is a little smaller than the Moon. Because it floats in the liquid metal of the outer core, it can spin at a different speed than the rest of the planet. 6In the 1930s, scientists discovered the Earth's core by studying changes in the speed of seismic waves as they travelled through the planet. The changes in speed showed that the core was a solid center made mostly of iron. 7The new research by Song and Yang studied what they called "repeated seismic waves from the early 1990s." They looked for changes in the amount of time seismic waves take to travel over the same paths inside the Earth. 8The scientists suggest changes in the spin of Earth's core can explain the changes in travel times. 9"We believe the inner core rotates, relative to the Earth's surface, back and forth, like a swing," they told The French news agency AFP. They added that its relative rotation changes about once every 35 years. 10They also said these changes correspond with very small changes in "length of day"-the exact amount of time it takes for Earth to rotate on its axis. 11Different research results 12In June 2022, John Vidale and Wei Wang, Earth scientists at the University of Southern California (USC), published a study in Science Advances. 13They reported that between 1969 and 1971 the core rotated more slowly than the outer layers. They also said that after 1971, the core rotated faster than the outer layers. In their study, Wang and Vidale used data on seismic waves from nuclear test explosions. 14Earth scientists say the Earth's core is difficult to understand and study. They disagree about how much, and how often, the spin might change. Some scientists argue that the speed of the spin does not change at all. They say the changes in seismic waves are caused by changes on the surface of the inner core instead of differences in how fast the core is spinning. 15Hrvoje Tkalcic is a geophysicist at the Australian National University. He thinks scientists will disagree about the latest research. 16He compared seismologists, who study earthquakes and seismic waves, to doctors "who study the internal organs of patients' bodies using imperfect or limited equipment." He added: "Our image of the inner Earth is still blurry." 17Song and Yang said scientists need years of seismic data to answer questions about Earth's core. 18Vidale of USC said, "Something's happening and I think we're going to figure it out. But it may take a decade." 19I'm Andrew Smith. 20Andrew Smith adapted this story for Learning English based on reporting from Agence France-Presse 21_______________________________________________________________ 22Words in This Story 23core -n. the very center of something 24spin -v. to turn 25seismic -adj. related to earthquakes 26swing -v. to move back and forth between two positions 27correspond with -v. (phrasal) to have a direct relationship to or with something or someone 28imperfect -adj. having some fault or incomplete part or area 29blurry -adj. unclear 30figure (something) out -v. (phrasal) to understand or find something by thought 31decade -n. a 10-year period 32______________________________________________________________ 33We want to hear from you. 34We have a new comment system. Here is how it works: 35Each time you return to comment on the Learning English site, you can use your account and see your comments and replies to them. Our comment policy is here.