Solid evidence in the inner core

摘要

The indications are that a solid ball of iron lies at Earth's centre. But only the identification of an elusive seismic signature can confirm the long-standing assumption that it is indeed solid. It is widely accepted that Earths inner core is solid. Seismologists have long been trying to find direct evidence of this assertion - which could come in the form of the identification of a particular kind of seismic wave, called a shear wave, travelling through the inner core. Perhaps, as reported by Wookey and Helffrich on page 873 of this issue, that elusive wave has now been teased out of the background seismic noise.