HR: 1340h
AN: G33A-0892    [Abstracts]
TI: Is the Earth Expanding ?
AU: * Shen, W
EM: wbshen@sgg.whu.edu.cn
AF: Wuhan University, Luoyu Road 129, Wuhan, HB 430079, China
AU: * Shen, W
EM: wbshen@sgg.whu.edu.cn
AF: Key Lab. of Geospace Environment and Geodesy, Luoyu Road 129, Wuhan, HB 430079, China
AU: Chen, W
EM: daniel135@126.com
AF: Wuhan University, Luoyu Road 129, Wuhan, HB 430079, China
AU: Li, J
EM: ljee000@163.com
AF: Wuhan University, Luoyu Road 129, Wuhan, HB 430079, China
AB: Whether the Earth is expanding or contracting is an interesting problem in geoscience. The information of the secular change of the Earth's gravity field supports the conclusion that the Earth is expanding at least in recent years. The gravitational potential could be expressed as a spherical harmonic series outside the Earth. In practical applications, it could be approximately realized by a truncated series, e.g., EGM96 (the Earth Gravity Model 96), EIGEN-GL04C, etc. The principal moments of inertia of the Earth are related to the second-order coeffients of the spherical harmonic series. Based on EGM96 as well as EIGEN-GL04C, the principal moments of inertia and especially their temporal variations are determined. All the three principal moments of inertia are gradually increasing at almost the same rate in recent 10 years, which might be due to the following three causes: 1) the rise of the sea level; 2) the increase of the total mass of the Earth; 3) the expansion of the Earth in the general sense. Calculations show that the rise of the sea level has too week influence on the variation of the principal moments of inertia comparing with the actual observations, and consequently the cause 1) could be given up. As to the increase of the total mass of the Earth, there does not exist any definite evidence, especially, it has not been found that the geocentric constant GM (where G and M are gravitational constant and the total mass of the Earth respectively) varies with time by various satellite approaches. Hence, it is reasonable to assume that the increase of the principal moments of inertia is caused by the expansion of the interior of the Earth or at least the whole mantle. This clearly demonstrates that the Earth is expanding at least in recent 10 years. Preliminary numerical calculations show that the Earth is expanding at the rate around 0.6 mm/yr at least in recent 10 years. Taking into account the Dirac's large number postulate, it could be concluded that the Earth expansion has and will have happened continuously in a long geological history.
DE: 0999 General or miscellaneous
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1299 General or miscellaneous (1709)
SC: Geodesy [G]
MN: 2007 Fall Meeting