Today we measure a room in meters, weigh coffee in grams and calculate distance in kilometers. And we assume that things work like stars fall. For centuries, each kingdom and sometimes each guild used its own unit of measurement. The cubit of Castile was not like the cubit of Aragon. The Galician vara had nothing to do with the Castilian vara. Commerce was chaos and we better not talk about science. Someone had to put order. And among those who did it, there was a Galician farmer from Lalín who, according to what they say, had a sublime head.
His name was Pedro Xosé Rodríguez González. History remembers him as the “Mathematician Rodríguez”, or the Mathematician of Bermés, after the parish of Lalín where he was born on October 25, 1770. He was the seventh child of a family of farmers from Pontevedra. Without money, without contacts, with the options that destiny reserved for the children of the Galician land of the 18th century: the countryside, emigration or the Church. How does a peasant child come to redefine the way of measuring the world?
Studious and without a cassock. His uncle, a well-read ecclesiastic, paid for his studies at the College of Humanities of Monforte de Lemos. From there he went to Santiago de Compostela at the age of 17, receiving a scholarship from the Colegio de los Jerónimos. There he studied grammar, Latin, philosophy, theology, subjects that opened doors to the priesthood. But the young man preferred math, studying self-taught, because the cassock did not fit among his concerns.
In 1798 he was already a substitute professor of sublime mathematics at the Faculty of Medicine of the University of Santiago. “Sublime“because it was literally the name of the degree: in the 18th and 19th centuries, the subjects of differential and integral calculus were grouped under this curious seal. In two years he won the chair by competitive examination. The court that examined him sent the following words to King Charles IV: “Rodríguez is one of those geniuses who from rare to rare forms the providence for sublime knowledge.” What a letter of introduction, great praise and confirmation that not even the Spanish Academy knew very well what to do with Galician.
What does a genius do in Spain in 1803. Well, ask for permission to go to Paris and continue learning. Rodríguez asked for it, got it and arrived in the French capital at the age of 33. There he entered the circle of the best scientists in Europe. He studied astronomy and mathematics under the tutelage of Jean-Baptiste Biot (we owe him knowledge about the polarization of light, meteorites, magnetic fields, etc.). He established a relationship with Pierre-Simon Laplace, who would end up becoming president of the Academy. That network was decisive.
In 1806, the Spanish government appointed him commissioner in an international expedition led by François Aragó and Biot himself. The mission was to extend the measurement of the Paris meridian arc, already drawn between Dunkirk and Barcelona, to the island of Formentera. The reason was deeper: that measurement would be the basis for establishing the exact length of the meter. The ten millionth part of the quadrant of the meridian passing through Paris. A measure taken from nature, not from any king’s span, by the way.
The Mediterranean is getting complicated. Now comes the part about the war, the espionage and an episode that seems straight out of an adventure novel. The team was going well, it formed geodesic triangle number 17, with vertices at the peaks of Camp Vell in Ibiza, La Mola in Formentera and La Mola del Esclop in Mallorca. It was the first time that a large geodesic triangle was measured over the sea. But in 1808, with Napoleon’s troops on the peninsula and the war of independence underway, scientists launching light signals from mountain peaks became immediate suspects.
Aragó, who was French, stayed in Mallorca to close the last triangle. The islanders said he was a spy. A Spanish member of the expedition ran to tell him. Aragó disguised himself as a peasant, went down the mountain and was about to capture him. He ended up detained in the Bellver castle, in the cell that Jovellanos occupied days before. Rodríguez maneuvered to help him out. The episode cost months of lost work. At least, measurement data was saved.
Is the Earth round or not? Neither round nor quite. In 1809, Rodríguez traveled to England on a government assignment: to examine British scientific establishments. What he did there was correct one of the most prestigious geographers of his time. Lieutenant Colonel William Mudge claimed, with his calculations of the Greenwich meridian, that the Earth was flattened at the Equator. Isaac Newton had said it the other way around decades before: flattening is at the poles. Rodríguez took Mudge’s observations, recalculated them with Delambre’s method and found a latitude error at the Arbury Hill station, Northamptonshire. Mudge’s error was demonstrable and Newton was right.
On June 4, 1812, the communication was presented to the Royal Society of London under the title ‘Observations on the measurement of three degrees of the meridian’. His friend José de Mendoza y Ríos, a Spanish sailor and member of the institution, read it. It is probably Rodríguez’s most important individual contribution to science: empirically demonstrating, and with greater accuracy than any other mathematician, the true shape of the Earth. From there he went to Göttingen to study crystallography under the supervision of the mineralogist Abraham Gottlob Werner. There he met another star of the time: Carl Friedrich Gauss. In Paris, in 1817, the father of modern crystallography, René Haüy, gave him a collection of 1,024 crystallographic models carved in wood. That collection is today in the Natural History Museum of the University of Santiago de Compostela. And it’s amazing.
A grave without a name. And we come to an ending that should make us ashamed. Tsar Alexander I offered him the direction of the Saint Petersburg Astronomical Observatory. The Paris Athenaeum of Sciences offered him the chair of Astronomy. And Rodríguez rejected both. He did not want to leave without notifying the Spanish government—to retain him, they appointed him director of the Madrid Astronomical Observatory in 1819. He was one of the founders of the Central University of Madrid, germ of the current Complutense. And between 1821 and 1823 he was a deputy for Galicia during the Liberal Triennium.
1823 arrives and Ferdinand VII restores absolutism. Rodríguez’s professorship will be withdrawn. Sick and without resources, he crosses the border to Portugal to work with the universities of Coimbra and Lisbon. He returned to Santiago in September 1824 and died on the 30th of that month. They buried him without any pomp in the church of San Agustín, under a tombstone without a name or inscription.
Forgotten and barely vindicated. In all of Spain there is only one street with his name, in Lalín, and a bust in the field of the Bermés festival – which, to make matters worse, it was fake and it took decades to change it. In the Auditorium of the University of Zaragoza he is carved with José Chaix, his companion in the meridian expedition. The Royal Galician Academy of Sciences elected him Galician Scientist of the Year in 2024two hundred years after his death.
It is dizzying to know that the meter used by any seamstress or architect was established, in part, thanks to this boy from the countryside of Lalín whom the University of Santiago court called a genius and whom a certain Spanish government, which destroyed an entire empire, left to die penniless. The first biographical news published following his death belongs to Ramón Neira de Mosquera, a personal friend, who published in the Santiago de Compostela newspaper ‘El Eco de Galicia’, 27 years after his death (April 24, 1851), an affectionate letter who recovered part of his legacy.
Image | Photo of the bust in the Bermés park
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