Chinese scientists have found that Earth's inner core wobbles around its rotational axis every 8.5 years. According to a study published in Nature Communications journal, a tiny misalignment between the inner core and the Earth's mantle, the layer below the crust, causes this movement.

Chinese scientists have found that Earth's inner core wobbles around its rotational axis every 8.5 years. According to a study published in Nature Communications journal, a tiny misalignment between the inner core and the Earth's mantle, the layer below the crust, causes this movement. Earth's core has two parts: a swirling liquid outer boundary and an almost solid inner layer. This region, starting 2,896 kilometres beneath the surface, is accountable for numerous geophysical dynamics of our planet, including the length of each day and Earth's magnetic field that protects humans from the Sun's harmful rays. The study noted that this shift can eventually alter the motion or shape of the liquid core, causing a change in the Earth's magnetic field. In 2019, Hao Ding of Wuhan University and his team of geophysical researchers examined the motion of Earth's rotational axis relative to its crust, also called polar rotation. They noticed a subtle deviation in polar rotation, which occurs every 8.5 years, leading to the discovery of "inner core wobble." To simplify things, the researchers have described the shift in Earth's inner core as similar to the wobble of a spinning top. ALSO READ | Spectacular! Japan's XRISM satellite provides first glimpse into X-ray cosmos Furthermore, Ding and his co-authors verified this cycle by measuring slight shifts in day length worldwide, controlled by the periodic movement of the Earth's rotational axis. They compared it to the deviations in polar motion. The researchers concluded that a tilt of 0.17 degrees between Earth's inner core and mantle causes this wobble. It rules out the traditional Earth rotation theory that "assumes that the rotation axis of the Earth's inner core and the rotation axis of the mantle coincide," Ding told Live Science. The research also suggests that the tilt implies that the inner core northern hemisphere might be a little denser than the rest of the layers, as there is a contrast between Earth's inner and outer core density. John Vale, a professor of Earth Science at the University of Southern California, told Live Science, "The new study helps discern the difference in composition between the metal in the solid inner and liquid outer core as well as estimates direction and speed of the wobble of the inner core." The research team did not consider atmospheric, oceanic, and hydrological influences that might have influenced the deviation in polar motion besides the inner core wobble. However, it's a crucial discovery as it could help researchers in the future comprehend the dynamics between Earth's inner core and natural events that impact humanity, like earthquakes. (With inputs from agencies)

Scientists might finally know why Earth's inner core wobbles every 8.5 years

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