The Shape of the Earth: From Erosthenes to the Space Age

Presentation by Kurt Lambeck
President
Australian Academy of Science, Australia

Abstract
The study of the shape of the Earth is called Geodesy. This may appear to be an arcane subject but it has been a matter of speculation and measurement for millennia. Its very foundation may well be Egypt. There are good practical reasons for knowing the shape and dimensions of our planet for mapping, navigation, satellite trajectory calculations, etc. But there is also a very significant science interest. The shape of the Earth is determined by its mass distribution – in the solid earth, and on the surface including oceans, ice sheets, atmosphere and ground and surface waters. As deformations occur within the planet and as surface mass is redistributed on its surface, the shape of the earth is modified. The shape, and its changes, is therefore an integrated expression of what happens in the Earth system. It therefore plays a central role in geology – to determine the density variations inside the crust and mantle and hence the stress-state of the planet and a measure of tectonic and geological zonation. As accuracies of measurement have improved, it also provides a measure of the redistribution of mass in the oceans – of changing currents and of changing sea levels – in the ice sheets, in the atmosphere – of seasonal exchanges in atmospheric mass between the hemispheres – and in ground and surface water storage. Monitoring the shape of the Earth is therefore also a monitoring of the environmental state of the planet.

In this lecture I will discuss some of the methods that have been used to measure the Earth and will focus on what has been learnt about the Earth itself and the relevance of this information to the monitoring of the state of the planet.

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Speaker’s profile
Kurt Lambeck is Distinguished Professor of Geophysics at the Australian National University.  His research interests range through the disciplines of geophysics, geodesy and geology with a focus on the deformations of the Earth on intermediate and long time scales and on the interactions between surface processes and the solid earth.

Professor Lambeck has been at the Australian National University since 1977, including ten years as Director of the Research School of Earth Sciences. He is currently also strategic science advisor to National Geospatial Reference System of Geoscience Australia and President of the Australian Academy of Science.

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