No, this is not about a resuscitation of old ideas about the history of planet Earth, but these days I could learn that the Earth Is Smaller Than Assumed, according to geodesist from the University of Bonn who have discovered that the blue planet is really smaller than originally thought. Well - not really, I would say: these guys are talking about 5 millimetre, or 0.2 inch.
Anyway, this accurate result is really impressive! It results from the combined analysis of radio signals from distant quasars, observed by a worldwide net of more than 70 radio telescopes. Characteristic features in the radio signals from quasars are received at slightly different times at different places on Earth, and the combination of these measurements using the technique of Very Long Baseline Interferometry allows a very precise determination of the relative distance of the radio telescopes: These relative distances can be deduced up to 2 millimetre on 1000 km, or up to 2 parts per billion (ppb). From the network of radio telescopes distributed all around the globe, it is possible to calculate its dimension very precisely. This analysis, accomplished with improved precision over previous similar work by the Bonn geodesist, yields a diameter of the Earth 5 millimetre smaller than supposed so far. According to a report in the New Scientist about this result, the total diameter of the Earth at the equator is around 12,756.274 kilometres (7,926.3812 miles).
Axel Nothnagel of the University of Bonn, who heads the team that provided new and more accurate data about the diameter of the Earth. (Credits: University of Bonn Press Release, July 5, 2007, Frank Luerweg)
A propos shrinking Earth: Earth was shrinking by a huge step, in a metaphorical way, 45 years ago today, as I heard this morning on the radio: On July 10, 1962, TELSTAR was launched from Cape Canaveral, the first communications satellite which allowed live TV broadcast between Europe and North America, bridging by the speed of light a distance that is steadily growing by 18 millimetre per year...
The TELSTAR communications satellite, launched 45 years ago today (Source: Wikipedia on Telstar)
PS: The paper by the Axel Nothnagel team is: The contribution of Very Long Baseline Interferometry to ITRF2005, by Markus Vennebusch, Sarah Böckmann and Axel Nothnagel, Journal of Geodesy 81 (2007) 553-564, DOI: 10.1007/s00190-006-0117-x. If someone can tell me where I can find the 5 millimetre in that paper, I am very grateful ;-)