News

Runner Up: Earthly revolutions

+ See all authors and affiliations

Science  20 Dec 1996:
Vol. 274, Issue 5295, pp. 1988
DOI: 10.1126/science.274.5295.1988f

If you think your day goes by too fast, consider that although the Earth spins once on its axis every 24 hours, it harbors at its center what is in essence a second planet: the inner core. In 1996, direct measurements of this mysterious crystalline-iron realm revealed that it rotates faster than the bulk of the planet, perhaps hastened by the magnetic effects of the molten outer core.

Clocking this swift rotation took patience, because the inner core gains a full turn on the rest of the planet only every 400 years. Seismologists depended on the woodlike grain of the inner core, which alters the speed of seismic waves passing through it, and compiled 30 years of data to pin down a change of a few tenths of a second in wave travel times.

The inner core's declaration of independence also accelerated theoretical studies. Computer models suggested that the magnetic field at the inner core is perhaps 200 times stronger than at the surface and may be the force hastening its rotation. Expect more revelations about Earth's final frontier as monitoring and modeling continue.

Quick spin.

Earth's inner core rotates faster than the rest of the planet.

ENGINEERING ANIMATION

ADDITIONAL READING

News Story:

  • R. A. Kerr, “Earth's Core Spins at Its Own Rate,” Science, 26 July 1996, p. 428.

Research Papers:

  • G. A. Glatzmaier and P. H. Roberts, “Rotation and Magnetism of Earth's Inner Core,” Science, 13 December 1996, p. 1887.

  • B. Romanowicz, X.-D. Li, J. Durek, “Anisotropy in the Inner Core: Could It Be Due To Low-Order Convection?” Science, 8 November 1996, p. 963.

  • X. Song and P. G. Richards, “Seismological Evidence for Differential Rotation of the Earth's Inner Core,” Nature 382, 221 (1996).

  • W.-J. Su, A. M. Dziewonski, R. Jeanloz, “Planet Within a Planet: Rotation of the Inner Core of Earth,” Science, 13 December 1996, p. 1883.

Link:

Navigate This Article