Programme details

The European Commission has decided to award the 2003 Descartes Prize to a project which is increasing our knowledge of the ways in which the Earth moves. Although it might not look that way, the Earth moves in space a bit like a wobbling top. This project is led by the Belgian scientist Véronique Dehant.

The Team

This research has gathered teams from the Royal Observatory of Belgium in Brussels, Belgium, the BIPM in Sèvres, the Observatory of Paris, the IMCCE in Paris, France, the Space Research Centre of the Polish Academy of Sciences in Warsaw, Poland, the University of Valladolid, the University of Alicante, the Complutense University of Madrid, Spain, the University of Dresden, the University of Munich, the Geoforschungszentrum in Potsdam, Germany, the Technical University of Vienna, Austria, the Academy of Sciences of the Czech Republic in Ondrejov, the National Academy of Sciences of Ukraine in Kiev, and the Moscow State University, Russia.

The Objective

The aim of this research is to develop a new model of nutation, in other words a model of the variations in the Earth's inclination in space. These variations are periodic, and are caused mainly by the effect that the gravitational attraction of the Moon and the Sun has on the Earth.

New Nutation Model

The new Nutation model being developped had to attain the accuracy which comparable to that of current observations. In 1980, when the old model was being used, we didn't have that kind of accuracy, it was more in the region of 10-20 metres, the sort of accuracy we need today is in the region of a centimetre.
To attain this accuracy they had to look beyond the attraction of the Moon and the Sun, and take into account other phenomena.

Impact of the Earth's Interior

The Earth's orientation in space can be compared with two spinning eggs. Two eggs won't spin in the same way. For the Earth it's exactly the same thing. In the Earth's interior there is a liquid core, and this liquid core accentuates the phenomenon of nutation.
It proved necessary to pool existing knowledge about the entrails of our planet and to bring together specialists from all the Earth sciences. Geophysicists like Pascal Defraigne looked at the structure of the Earth's interior in search of phenomena which might affect nutation.

Earth's Interior

This research has led to an improved understanding of the structure of the Earth's interior.
Véronique Dehant :
While developing this model, we discovered quite a number of things about the dynamics of the Earth's interior, and in particular we have managed to obtain information about the shape and size of the Earth's liquid outer core, and about the existence and amplitude of an electromagnetic field at the boundary between the solid inner core and the liquid outer core.

Impact of Atmosphere and Oceans

Three mechanisms of interaction between the Earth, the atmosphere and the oceans have a noticeable effect on the nutations.
The first mechanism is friction, the wind at the Earth's surface, and ocean currents, drag the Earth along with them.
The second mechanism is due to the pressure of the atmosphere and of seawater at the Earth's surface and on the sea floor.
The third effect is the interaction between the masses in the Earth and the masses in the atmosphere.

Conclusion

The nutation model will mainly be of benefit to astronomers, geophysicists and engineers. For the general public it will mean better navigation systems, both for GPS and for the future European system, GALILEO.