Jan 192021

Today is the birthday (1775) of André-Marie Ampère, a French physicist and mathematician who was one of the founders of the science of classical electromagnetism, which he referred to as “electrodynamics”. He is also the inventor of numerous applications, such as the solenoid (a term coined by him) and the electrical telegraph. Ampère was a member of the French Academy of Sciences and professor at the École polytechnique and the Collège de France. The SI unit of measurement of electric current, the ampere, is named after him. His name is also one of the 72 names inscribed on the Eiffel Tower.

Ampère was born to Jean-Jacques Ampère, a prosperous businessman, and Jeanne Antoinette Desutières-Sarcey Ampère, during the height of the French Enlightenment. He spent his childhood and adolescence at the family property at Poleymieux-au-Mont-d’Or near Lyon. Jean-Jacques Ampère was an admirer of the philosophy of Jean-Jacques Rousseau, whose theories of education (as outlined in his treatise Émile) were the basis of Ampère’s education. Rousseau believed that young boys should avoid formal schooling and pursue instead an “education direct from nature.” Ampère’s father actualized this ideal by allowing his son to educate himself within the walls of his well-stocked library. In addition, Ampère used his access to the latest books to begin teaching himself advanced mathematics at age 12. In later life Ampère claimed that he knew as much about mathematics and science when he was eighteen as he ever knew, but as a polymath, his reading embraced history, travels, poetry, philosophy, and the natural sciences. The French Revolution that began during his youth was influential: Ampère’s father was called into public service by the new revolutionary government, becoming a justice of the peace in a small town near Lyon. When the Jacobin faction seized control of the Revolutionary government in 1792, his father resisted the new political tides, and he was guillotined on 24 November 1793, as part of the Jacobin purges of the period.

in July 1803, Ampère moved to Paris, where he began a tutoring post at the new École Polytechnique in 1804. Despite his lack of formal qualifications, Ampère was appointed a professor of mathematics at the school in 1809. As well as holding positions at this school until 1828, in 1819 and 1820 Ampère offered courses in philosophy and astronomy, respectively, at the University of Paris, and in 1824 he was elected to the prestigious chair in experimental physics at the Collège de France. In 1814 Ampère was invited to join the class of mathematicians in the new Institut Impérial, the umbrella under which the reformed state Academy of Sciences would sit.

In September 1820, Ampère’s friend and eventual eulogist François Arago showed the members of the French Academy of Sciences the surprising discovery of Danish physicist Hans Christian Ørsted that a magnetic needle is deflected by an adjacent electric current. Ampère began developing a mathematical and physical theory to understand the relationship between electricity and magnetism. Furthering Ørsted’s experimental work, Ampère showed that two parallel wires carrying electric currents attract or repel each other, depending on whether the currents flow in the same or opposite directions, respectively – this laid the foundation of electrodynamics. He also applied mathematics in generalizing physical laws from these experimental results. The most important of these was the principle that came to be called Ampère’s law, which states that the mutual action of two lengths of current-carrying wire is proportional to their lengths and to the intensities of their currents. Ampère also applied this same principle to magnetism, showing the harmony between his law and French physicist Charles Augustin de Coulomb’s law of magnetic action. Ampère’s devotion to, and skill with, experimental techniques anchored his science within the emerging fields of experimental physics.

Ampère also provided a physical understanding of the electromagnetic relationship, theorizing the existence of an “electrodynamic molecule” (the forerunner of the idea of the electron) that served as the component element of both electricity and magnetism. Using this physical explanation of electromagnetic motion, Ampère developed a physical account of electromagnetic phenomena that was both empirically demonstrable and mathematically predictive. In 1827 Ampère published his magnum opus, Mémoire sur la théorie mathématique des phénomènes électrodynamiques uniquement déduite de l’experience (Memoir on the Mathematical Theory of Electrodynamic Phenomena, Uniquely Deduced from Experience), the work that coined the name of his new science, electrodynamics, and became known ever after as its founding treatise.

In 1827 Ampère was elected a Foreign Member of the Royal Society and in 1828, a foreign member of the Royal Swedish Academy of Science.

Ampère was from the general region of Lyon, and “Lyonnaise” refers to cooking traditions and practices centering on the area around Lyon. In the 16th century, Catherine de Medici brought cooks from Florence to her court in Lyon and they prepared dishes combining the agricultural products from the regions of France with their own culinary expertise. Now “Lyonnaise” is a semi-formal appellation. Sauce Lyonnaise, for example, involves a demi-glace, vinegar, and onions.  This video explains the appellation more fully and shows the making of veal cutlets Lyonnaise.

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