Abstract
KE. BULLEN has examined the recent develop-? ments in knowledge of the earth's interior (Ada Astronomica,4, April 1939). The most recent estimate of Gutenberg and Richter shows a radius of the core of 2,920 km., and work on near earthquakes suggests the existence of various crustal layers extending to a depth of the order of 30 km. from the surface of the earth. According to Bullen, if the variation of density between the earth's crustal layers and the central core were continuous, the moment of inertia of the central core wouldhave to beO –57 Ma2,where ?is mass of core and ais radius of core. This, being in excess of the value 0-40 Ma2which would hold for a homogeneous sphere, would appear to indicate a virtually impossible distribution of matter inside the central core. Thus some assumption made in obtaining these estimates appeared to need amendment. The amendment suggested by Bullen is that there is a change of material at a depth of the order of several hundred kilometres.
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The Earth's Interior. Nature 145, 599 (1940). https://doi.org/10.1038/145599a0
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DOI: https://doi.org/10.1038/145599a0