Earth s spinning innards

in spite of tremendous advancements in the technology of seismological tools, the deepest interior of the earth has remained inaccessible to geophysicists. So, when a team of seismologists led by Xiao Dong Song and Paul Richards of the Lamont Doherty Earth Observatory at Columbia University, New York, us , announced that the solid iron core of the earth spins faster than the rest of the planet, gaining a lead of almost a tenth of a rotation in the last three decades, it generated lot of excitement among geophysicists ( Science , Vol 273, No 5274).

Theoreticians had predicted that the innermost core rotates faster than the rest of the planet, but they too are taken aback by the high speed of rotation. This, according to David Stevenson, a planetary physicist at the California Institute of Technology, us , will pose additional constraints while making models of earth's magnetic field, which is generated in the molten-iron outer core. The new rotation rate can lead to the measurement of the strength of the magnetic field inside the core, which till date has been a matter of conjecture.

Dong and Richards set out to measure the rotation speed armed with two well known facts about the earth's interior. Firstly, for several years now seismologists have been showing how the crystalline iron of the inner core has a