The Earth as an Ellipsoid
During travels throughout Europe, Celsius became aquainted with Pierre Louis de Maupertuis, a French astronomer who supported Sir Isaac Newton's theory that the Earth was elongated near the equator and flatter near the north and south poles. There were many disputes about this theory, so in 1736 Maupertuis led an expedition on which he invited Celsius to join him.
The purpose of this expedition was to measure the length of a degree along a meridian close to the pole. Their measurements were compared to the measurements of another group of scientists on a similar expedition near the equator. These two expeditions were able to confirm Newton's theory that the Earth is in the shape of an ellipsoid flattened at the pole.
