Earth smaller than thought, researchers find
The Earth is smaller than previously thought, according to new research from scientists at the University of Bonn in Germany who have just remeasured our planet. Although the discrepancy is small, just a few millimetres, it is nevertheless important for scientists wishing to measure sea level rise for example. The measurements were made using a technique called VLBI, which stands for Very Long Baseline Interferometry, in which radio waves are transmitted into space from sources called Quasars. These radio waves are received by a network of over 70 radio telescopes. Due to the vast distances between the gaging stations, the radio signals are received with a slight time delay. 'From this difference we can measure the distance between the radio telescopes - and to the preciseness of two millimetres per 1,000 kilometres,' said lead researcher Dr Axel Nothnagel of the university's Geodesy Institute. By knowing the distances between the gaging stations, the researchers are able to determine the size of the Earth or the exact location of the centre of the Earth. The system also allows researchers to demonstrate, for example, that Europe and North America are moving apart at a rate of around 18 mm a year. 'We have analysed the measurements and calculations from 34 partners in 17 countries,' said Dr Nothnagel. 'A combination of GPS and satellite laser measurements will enable the availability of the coordinates from almost 400 points on the surface of the Earth with unparalleled exactness.' This information will provide the basis for a new coordinates system for the planet which will allow the track of Altimeter Satellites to be determined extremely precisely. Altimeter Satellites measure their altitude over the Earth's surface and so can measure changes in sea level. However, if the satellite deviates from its flight path, for example by flying higher than it should, there will be errors in the data. The study is published in the Journal of Geodesy.
Countries
Germany