Geoscience Reference
In-Depth Information
Observatory. Laplace accepted the proposal by Biot and Arago and they set off to
measure the southern sector of the Paris Meridian in the Mediterranean. Arago's
part as a young man in making these measurements (at the start of which he cele-
brated his 20th birthday) seems like an adventure story; the work turned out to be
more dangerous than it would have seemed, even by the standards of the age.
People
Pierre-Simon Laplace (1749-1827)
A brilliant mathematician, Laplace had worked on differential equations and the stability of
the solar system. He was the author of the
Nebula Hypothesis
, which envisioned that the
solar system formed from condensations in a flat rotating nebula, a theory which foreshad-
owed the modern concept. In 1790 Laplace had been a member of the committee of the
Academy of Sciences to standardize weights and measures, but along with Lavoisier, Borda,
Coulomb, and Delambre, he had been thrown off because their Republican credentials were
not good enough. Laplace lived 75 km from Paris and wisely stayed there during the Reign
of Terror, thus escaping the guillotine, and in 1795 when the Academy was revived and
established the Bureau de Longitudes, Laplace joined its staff and became director.
ARAGO AND BIOT set out for Spain from Paris early in 1806 and visited some of
Méchain's stations on the way to re-measure some of his triangulations. In Spain
they were joined by two Spanish Commissioners, Señores Chaix and Rodriguez,
who brought with them the scientific instruments left by Méchain. Biot and Arago
scaled one of the bleakest mountains near Valencia, the Desierto de las Palmas,
where Méchain had created a triangulation base by levelling a small platform. They
attempted to measure from the coast across the Mediterranean Sea to the Balearic
Islands, where Chaix and Rodriguez climbed Mount Campvey. The light that had
been installed during Méchain's expedition was difficult to locate and to see reliably
because its optical system had been misaligned. The light on Mount Campvey was
on the island of Ibiza, 150 km across the sea from Desierto de las Palmas on the
coast of the Spanish peninsula, and Arago and Biot could not see it for months
through the atmospheric absorption.
“It will be easily imagined what must be the ennui experienced by a young and
active astronomer, confined to an elevated peak, having for his walk only a space
of twenty square meters, and for diversion only the conversation of two Carthusians,
whose monastery was situated at the foot of the mountain, and who came in secret,
infringing the rule of their order,” wrote Arago in his autobiography. The two
monks came separately to talk with Arago and Biot, but, each one learning that the
other had infringed the rule of silence, they both conspired not to report each other.
The younger man was a reluctant monk, forced into the order by his family. In front
of Arago and Biot he relayed anti-religious sentiment based on information he had
gathered while taking confessions. Biot suspected him of being an agent-provocateur
and sharply turned the conversation to a different topic. The next day, Arago had to
persuade the monk to lay aside a gun with which he had murderous intentions
towards Biot. The older monk was no more moral than the younger; Arago records
his disgust and caution at being invited during mass conducted by this man to join
him in drinking more wine than was part of the sacrament. The disgust rose from
religious feelings of respect for the mass, the caution from a suspicion that the wine
might be poisoned in revenge for Biot's rebukes.
