SHAPE OF THE EARTH:
The Enlightenment
The theory
The results
Later research

Later research

The result of de Maupertuis’ experiments was met with great enthusiasm in the French scientific community. Before long the deviance of the result from other corresponding experiments gave reason to assume that the result might contain errors. Compared to Cassini’s result the de Maupertuis expedition presented a flattening ratio of 1/123 as that of the Peruvian expedition was 1/300. This was so big a deviance and led to suspicions of errors in de Maupertuis’ measurements. Other measurements of that era also came close to the results achieved by the expedition to Peru.

On the ground of this the Swedish Academy of Science planned new measurements as early as in the 1740’s. The project was undertaken only in 1801 when Jöns Svanberg was commissioned the measurements in the Tornionlaakso Valley. He used 22 measuring points instead of 11 used by de Maupertuis. Svanberg’s result was 57 196,159 toise, i.e. 209 toise (407,30 m) shorter than that of the Frenchmen.

The Finn Yrjö Leinberg carried out some re-measurements in 1928. He concludes that de Maupertuis’ result , too long by 400 meters, was due to the following error factors:

There was an error in the calculations of the triangular measurements. This is why the distance between Kittisvaara and Tornio de Maupertuis states is 45 meters loo long. The biggest error was caused by the change of degree zero of the sector during the transport. The error was 7’87’’. An error of over 2’ also resulted from the deviance of the vertical line between Tornio and Kittisvaara, a fact Maupertuis had no way of knowing of.

By the mid 1900’s an exact value of 1/298,25 for the earth’s flattening could be attained with the help of triangular measurement and astronomical observations. After this the measurements have been made by the satellites and the triangular measurement has become a method of the past.

Monument in Kittisvaara

Monument of Maupertuis