Size matters ... Our planet isn`t as big as we thought.
- World`s diameter 5mm smaller than we thought
- Figure vital for monitoring climate change
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THE world is smaller than first thought, according to German researchers at the University of Bonn.
They took part in an international project to measure the diameter of the world that showed it is 5mm smaller than the last measurement made five years ago.
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Dr Axel Nothnagel, who led the Bonn researchers, said the difference was crucial in the study of climate change.
"It may seem a very small difference, but it is essential for the positioning of the satellites that can measure rises in sea level," he said.
"They must be accurate to the millimetre. If the ground stations tracking the satellites are not accurate to the millimetre, then the satellites cannot be accurate either."
The scientists have rounded the diameter measurement up to 12,756.274km for the general public.
The system of measurement used by the Bonn geodesists in the two-year project consisted of radio waves transmitted into space.
"A network of more than 70 radio telescopes worldwide receives these waves. Because the gauging stations are so far apart from each other, the radio signals are received with a slight time-lag," Dr Nothnagel said.
"From this difference we can measure the distance between the radio telescopes to the preciseness of 2mm per 1000km."
The procedure is called VLBI, which stands for "Very Long Baseline Interferometry". The technique can be used, for example, to demonstrate that Europe and North America are moving apart at a rate of about 18mm a year.
