A Gravitational Battle Within the Earth Is Changing the Length of Days
Geophysicists have identified a gravitational interaction between the Earth's inner core and the mantle as a potential cause for fluctuations in the planet's rotation. This mechanism helps explain long-term variations in the length of days that were previously attributed only to surface-level factors.
Why it matters
Understanding the internal dynamics of the Earth provides deeper insight into planetary physics and the factors influencing global timekeeping.
Scientists have already pinpointed a handful of compounding causes. Fluctuations in the atmosphere and oceans can slightly speed up or slow down the Earth’s rotation; major earthquakes can redistribute part of the planet’s mass; and by depositing enormous amounts of water into the oceans, melting continental ice is also a factor.
These influences account for some of the more sudden and recent changes, but on a several decades-long timescale, some of the variation appears to originate from a source much deeper within the Earth. Beneath our planet’s rocky mantle lies the outer core—a 1,400 mile thick layer of ultra-hot liquid metal that is in constant motion. As these flows change, they can slightly alter the speed at which the rest of the planet rotates.
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