Philippe of Hire

Biography

His/her father, Laurent of Hire (1606-1656), is a famous artist. Philippe studies initially painting with Rome where it had gone in 1660 for health reason.

He leaves on a journey to Uraniborg in 1671, and determines for the first time a precise longitude. He will bring back to Paris a young Danish astronomer, Ole Christensen Rømer (1644-1710) which will give, while working with Jean-Dominique Cassini, a reasonable approximation, within sight of the means of the time, the Speed of light, approximately 228.000 km/s.

On its return to Paris, it starts to study sciences and humanities and shows in particular a great inclination for the Mathématiques. It becomes acquainted with a disciple of Desargues, the engraver Abraham Bosse, and in its instigation a theory of the cut of the voussoirs of the rampant arches publishes treated by the geometry of the Conique S (1672).

Its more important work concerns indeed the Géométrie. He is the continuator of Girard Desargues (1591-1661) and of Blaise Pascal (1623-1662) in geometry of conical, in what he deduces the properties from conical starting from the properties from the circle. Hire innovates by reports/ratios with its two precursors, in what it exploits to the maximum the properties of invariance of the harmonic Division, which enables him to reason almost only in the plan (and not in space). This approach leads it to develop the concepts of poles and polar S, of homology, orthoptic place, etc

Hire was also interested in the geometry of Descartes and the algebraic curves, but criticized, in the years 1690, the infinitesimal calculus in its shape of “calculation of the infinitely smalls”, which was worth to him to be arranged by Varignon with the number of the “mathematicians of the old man stile ”.

As a mechanic of the theory of the epicycloidal Gears S, it continues work of Christiaan Huygens (1629-1695). In France, one allots the hypocycloidal train to him whose interior wheel has a ray half of the basic wheel, the center of travelling describing a periodic translation.

It is made member of the Academy of Science in 1678.

He teaches with the Collège de France and the Academy of architecture starting from 1687.

Its work at the Observatory: recorded of the temperatures day laborers, pluviometry, etc make it pass for the founder of meteorology.

Hire studies the development and the increase in the stems of the plants. Its observations contradict those of Denis Dodart (1634-1707); this is why Hire publishes the report of its work only after the death of this one. On the causes of the perpendicularity of the stems compared to the horizon is published in 1708.

Two of its sons will also follow a scientific career: Gabriel-Philippe of Hire (1677-1719) is mathematician and Jean-Nicolas of Hire (1685-1727) is also botanist. Augustin of Hire, as for him, will be civil engineer, dealing in particular with the correction of banks of the Drac, in Grenoble.

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