Geoscience Reference
In-Depth Information
The Cassinis' calculations about the shape of the Earth in 1701 and 1722 did not
change Newton's mind after the first edition of
Principia
had been published. In the
second and third editions he stuck to his guns; the pendulum observations seemed
more conclusive than the geodetic measurements. He cited observations of the
length of the seconds pendulum that had been made in places widely dispersed
across the globe: St Helena, Guadeloupe, Paris, Cayenne, Martinique, Lisbon,
Paraìba, Grenada, St Kitts, Santo Domingo, and Portobello. By contrast, the geodetic
measurements all had to be taken within the confines of France, with the changes of
scale from its south to its north being too small to determine accurately.
VOLTAIRE DESCRIBED the battle between the Newtonian view of the shape of the
Earth and the reason that underpinned it, namely the theory of gravity, versus the
geodesic measurement and the Cartesian theory of gravity (insofar as it was part of
the argument). He cast the battle in national terms, pegged as a fight between Britain
and France. Others saw it in the same way; for example, the secretary of the Academy,
Bernard Le Bovier de Fontenelle, rhetorically demanded to know why some French
people wanted “to justify the English at the expense of the French? Who would ever
had thought it necessary to pray to Heaven to preserve Frenchmen from a too favorable
bias for an incomprehensible system, they who have so dearly, and for a System origi-
nating in a foreign land, they who have been charged with loving only that which is
their own?” This view of the intellectual argument has been followed ever since.
However, this was not wholly a battle between England and France. In France,
Newton's work was known and much admired, and his theory of gravity was
defended against Mairan by French astronomers Joseph-Nicholas Delisle, Alexis-
Claude Clairaut, and, leading the attack, Pierre Maupertuis.
People
Alexis-Claude Clairaut (1713-1765)
Like his father, Clairaut was a mathematician, a child prodigy who read his first paper to
the Academy of Sciences at the age of 12 and became a member at 18. He was a friend of
Maupertuis and joined him in his belligerent advocacy of Newton's theories; they were two
of a kind, both vivacious and attractive to women. After the expedition to Lapland, Clairaut
published the theoretical interpretation of the measurements in
Théorie de la Figure de la
Terre
(1743), considered a scientific classic. He developed the theory of the orbit of the
Moon around the Earth, a technically difficult work of Newtonian mathematics because of
the gravitational attraction of the Sun and the non-spherical shape of the Earth. In develop-
ing a theory to solve the so-called three-body problem of the mutual gravitational interac-
tion of three bodies, he applied it to the reappearance of Halley's Comet, uncertain in its
orbit around the Sun because of the attraction of Jupiter (and Saturn). His predictions of its
reappearance reduced the error from a year to two weeks or less.
In the 1720's, the French mathematician Pierre Maupertuis was systematically
building up for himself a reputation as a mathematician (Terrall 2002). His interests
were wide and he cultivated an extensive network of social contacts among the
French academic society elite. In the summer of 1728, he visited London for twelve
weeks to broaden his network of influential colleagues among the Newtonian
scientists of the Royal Society; Maupertuis undoubtedly discussed Newton's theory
of gravity with the English scientists and certainly became familiar with the finely
crafted instruments they used to make astronomical measurements.
