Length of Earth's day is changing – scientists' discovery
An international group of geophysicists has revealed the mechanism explaining microscopic fluctuations in the length of Earth's days. The study showed that gravitational interaction between the solid inner core and the mantle creates a rotational torque that changes the planet's rotation speed. The discovery closes a long-standing gap in geophysics.
An international team of scientists has revealed the mechanism explaining microscopic fluctuations in the length of Earth's days. Geophysicists have known for three decades that the liquid outer core periodically accelerates and decelerates, and the mantle compensates for these shifts to conserve angular momentum, which changes the length of the day. However, the mechanism of force transfer remained a mystery—ordinary friction between the core and mantle is too small. The study showed that the answer lies in gravitational interaction: the solid inner core rotates at a different speed, creating a displacement relative to dense anomalies in the mantle. Gravitational forces push the planet's layers, generating a rotational torque. External factors affecting rotation speed include seasonal atmospheric movements, ocean currents, glacial melting, and earthquakes. The discovery allows for more accurate modeling of the planet's long-term dynamics.