Pierre Louis Maupertuis and the trip to Tornio

Pierre Louis de Maupertuis

Pierre Louis de Maupertuis was born 28 September 1698 in Saint Malo, France. He was a French philosopher, mathematician and geodesist who became a member of the French Academy of Sciences in Paris in 1731. In 1732 he introduced Newton’s theory of gravitation to France.

He was sent out to Lapland to determine, with as exact measurement as possible, the shape of the Earth at the poles. This trip took place between the years 1736 and 1737.

Maupertuis gained fame for his expedition and he was invited to Germany by Frederick the Great. He became a member of the Berlin Academy of Sciences in 1741 and served as its president from 1745 to 1753.

In 1744 he first enunciated the Principle of the Least Action and he published it in Essai de cosmologie in 1750. Maupertuis was accused by Samuel König of plagiarising Wilhelm Leibniz’s work but Leonard Euler defended him. Voltaire was so critical of Maupertuis’ work that eventually Maupertuis left Berlin in 1753.

Maupertuis died 27 July 1759 in Basel, Switzerland.

The meaning of the trip

The reason for this trip was the scientific brouhaha between two scientists. According to the French philosopher René Descartes (1596–1650) theory the Earth by spinnig its own axis, take the shape of a lemon.

The English scientists Isaac Newton’s theory was different. He thought that the centrifugal force leads to the enormous mass of the Earth swelling out at the equator, flattening the poles, and giving the Earth a similar shape to that of an orange.

To prove the Newton’s theory the French Academy of Sciences sent two expeditions to measure the length of a degree along the meridian. One expedition was sent to equator to Peru (now Ecuador) led by Pierre Cassini and Charles-Marie de La Condamine and other expedition led by Maupertuis was sent to near the pole to Tornio in Finland.

If the length of a meridian in the vicinity of the Arctic Circle were longer than a degree along the same meridian in France, or close to the equator, this would confirm Newton’s "Orange theory"; if the opposite were true, it would confirm Cartesius’ "Lemon theory".

The group members

There were 36 people in the group. With Maupertuis there were another three French scholars- Charles Etienne Louis Camus, an astronomer Charles Le Monnier and a mathematical child prodigy. There were also Anders Celsius, a Swedish astronomer and physicist. He is known by the thermometer.

A priest Réginald Outhier worked in the group as a physician of the soul and he kept travel journal. He also was the only one who had experience of mapping.

The Swedish scientist Anders Hellant was an interpreter. He spoke Finnish, French, Swedish and Latin. The other interpreter was mayor of Tornio, Petter Johan Pipping. He spoke Swedish, Finnish and Latin.

Sommeraux worked as a secretary and cash keeper. D´Merbelot was a drawer. All together there were 8 researchers, 2 interpreters, 5 servants and 21 oarsmen.

When the expedition came to Tornio

In June 1736 the expedition came to Tornio. They were ready for to travel up the river and they had seven boats with them. Food instruments and other equipments were loaded on the boats, and there were three rowers in each boat. This was an exciting event for all the citizens of Tornio. They saw the beginning of the adventure and they wondered what these men were doing in their town.

Before the real adventure, Maupertuis had had time to make a trip to Aavasaksa with the governor Gabriel Gyllengrip. He had saw couple of high places, which he thought would be perfect for his "triangle". Still it was questionable how the research would succeed.

Life in Tornio

The Frenchmen spent the winter in Tornio, where they led a lively social life. Maupertuis and his friends became friends with the locals and they had respecting attitude towards them. The citizens arranged parties and other activities for the foreigners. The highest officers spoked Latin and French, so they could talk with the members of the expedition. Maupertuis was a popular socialite, who recited his own poems and accompanied himself and the guitar. The company left Tornio at midsummer 1737. During the time, the two daughters of the merchant Planström had fallen in love with two gentlemen and travelled after them all the way to Paris.

The network of triangles

The expedition built up a network of triangles starting from the church steeple in Tornio in the south, and the mountain of Kittisvaara near Pello town, just over 100 kms further north. From the network of triangles they determined the graduated arc of the meridian. Two measuring groups did the detailed measurement of the triangle’s base around Christmas of 1736.

The results

Both expeditions determined the length of the arcs using the method of triangulation. Astronomic observations for latitude determinations from which the size of the angles was computed were made using the zenith sectors having radii up to four metres. Maupertuis reported that the length of one degree of meridian in Lapland was 57,437.9 (The toise was an old unit equal to 1.949 metres). This result was compared to the corresponding value of value of 57,060 toises near Paris, proved Newton’s "Orange theory".

Later, large errors were found in the measurement, but they were in the "right direction"

Monuments

The monument of the measuring of degrees is situated in Tornio, opposite to the church. Another monument is in Kittisvaara, and it has been set up in 1956.

By Riitta Nykänen and Anna Tenhonen