1796 in science

The year 1796 in science and technology involved some significant events.

Astronomy

Pierre-Simon Laplace publishes Exposition du système du monde, his work on astronomy following Newton and Lagrange. He develops an analytical theory of tides, deduces the mass of the Moon, improves the calculation of cosmic orbits, and predicts that Saturn's rings will be found to rotate. Most notably, he propounds the modern nebular hypothesis, independently outlined by Kant.

This is a productive year for the German mathematician Carl Friedrich Gauss and his work in number theory:
* March 30 – He obtains conditions for the constructibility by ruler and compass of regular polygons, including the heptadecagon.
* April 8 – He becomes the first to prove the quadratic reciprocity law, enabling determination of the solvability of any quadratic equation in modular arithmetic.
* May 31 – He puts forward his prime number theorem on the distribution of prime numbers among the integers.
* July 10 – He discovers that every positive integer is representable as a sum of at most three triangular numbers, noting in his diary "Heureka! num = Δ + Δ + Δ."
* October 1 – He publishes a result on the number of solutions of polynomials with coefficients in finite fields.
Adrien-Marie Legendre conjectures the prime number theorem.

May 14 – Edward Jenner administers the first smallpox vaccination.
Franz Joseph Gall develops his theory of 'cranioscopy', a forerunner of phrenology.
The Retreat established in York, England; it pioneers the humane treatment of people with mental disorders.

April 4 – Georges Cuvier reads his paper Mémoires sur les espèces d'éléphants vivants et fossiles at the opening of the Institut National in Paris, demonstrating that species had become extinct.

Completion of the first cast iron aqueducts, on the English canals
* February – Holmes Aqueduct on the Derby Canal, designed by Benjamin Outram.
* March – Longdon-on-Tern Aqueduct on the Shrewsbury Canal, designed by Thomas Telford.
August 9 – Opening to traffic of the Wearmouth Bridge in England, designed by Thomas Paine in cast iron. The second in this material built after that at Ironbridge, but over twice as long, its span of 237 feet makes it the world's longest single-span vehicular bridge extant at this date.
Printing by lithography is invented by Alois Senefelder in Bohemia.

Pierre André Latreille publishes Précis des caractères génériques des insectes, disposés dans un ordre naturel.