Spiru C. Haret (; 15 February 1851 – 17 December 1912) was a Romanian mathematician, astronomer, and politician. He made a fundamental contribution to the n-body problem in celestial mechanics by proving that using a third degree approximation for the disturbing forces implies instability of the major axes of the orbits, and by introducing the concept of secular perturbations in relation to this. As a politician, during his three terms as Minister of Education, Haret ran deep reforms, building the modern Romanian education system. He was made a full member of the Romanian Academy in 1892. He also founded the Bucharest Observatory, appointing as its first director. The crater Haret on the Moon is named after him. Life Haret was born in Iași, Moldavia, to Constantin and Smaranda Haret, who were of Armenian origin. His baptismal record listed his name as Spiridon Haret. He started his studies in Dorohoi Iași, and in 1862 moved to Saint Sava High School in Bucharest. He showed an early talent for mathematics, publishing two textbooks (one in algebra and one in trigonometry) when he was still a high school student. In 1869 he entered the University of Bucharest, where he studied physics and mathematics. In 1870, while a student in his second term, he became teacher of mathematics at the Nifon Seminary in Bucharest, but quit the following year in order to continue his studies. In 1874, at age 23, he graduated with a degree in physics and mathematics. After graduation, Haret won a scholarship competition organized by Titu Maiorescu and went to Paris in order to study mathematics at the Sorbonne. There he earned a mathematics diploma in 1875 and a physics diploma in 1876. Two years later (on 18 January 1878), he earned his Ph.D. by defending his thesis, Sur l’invariabilité des grandes axes des orbites planétaires (On the invariability of the major axis of planetary orbits), in front of examiners led by Victor Puiseux, his Ph.D. advisor. In this work he proved a result fundamental for the n-body problem in astronomy, the thesis being published in volume 18 of Annales de l'Observatoire de Paris. Haret was the first Romanian to obtain a Ph.D. degree in Paris. After his return to Romania in 1878, Haret largely abandoned scientific research and dedicated the rest of his life to improving Romanian education, which was heavily underdeveloped at the time, both as professor and as