1809 in science

The year 1809 in science and technology involved some significant events, listed below.

Astronomy

• Carl Friedrich Gauss publishes Template:Lang in Hamburg, introducing the Gaussian gravitational constant and containing an influential treatment of the least squares method.<ref name=tt>Template:Cite book</ref>
• S. D. Poisson publishes Template:Lang and Template:Lang in the Journal of the École Polytechnique, extending Lagrange's theory of planetary orbits.

Biology

• Jean-Baptiste Lamarck publishes Philosophie Zoologique, outlining his theory of evolution.
• Johann Heinrich Friedrich Link first describes Penicillium.<ref>Template:Cite journal</ref>

Geology

• William Maclure publishes the first geological map of the United States with accompanying memoir.<ref name=tt/><ref>Template:Cite journal</ref>

Mathematics

• Louis Poinsot describes the two remaining Kepler-Poinsot polyhedra.

Medicine

• December 25 – American physician Ephraim McDowell performs the world's first ovariotomy, the removal of an ovarian tumor.<ref>Template:Cite journal</ref>
• Philippe Pinel publishes accounts of what would later be regarded as schizophrenia.<ref>Template:Cite journal</ref>

Technology

• February 11 – Robert Fulton patents the steamboat in the United States.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>
• May 5 – Mary Kies becomes one of the first women granted a U.S. patent, for a technique of weaving straw hats with silk and thread.<ref>Template:Cite web</ref>
• Samuel Thomas von Sömmerring invents a water voltameter electrical telegraph.<ref name=tt/>
• William Hyde Wollaston invents the reflecting goniometer.

Awards

• Copley Medal: Edward Troughton<ref>Template:Cite web</ref>

Births

• January 4 – Louis Braille (died 1852), French inventor.
• January 6 – Marie Durocher (died 1893), Brazilian physician.
• February 12 – Charles Darwin (died 1882), English naturalist.
• February 15 – Cyrus McCormick (died 1884), American inventor.
• February 21 – Carl Ernst Bock (died 1874), German physician and anatomist.
• April 7 – James Glaisher (died 1903), English meteorologist and balloonist.
• April 15 – Hermann Grassmann (died 1877), German mathematician.
• April 20 – James David Forbes (died 1868), Scottish physicist, glaciologist and seismologist.
• August 29 – Oliver Wendell Holmes Sr. (died 1894), American physician and writer.
• November 22 – Bénédict Morel (died 1873), French psychiatrist.
• Date unknown – William Lobb (died 1864), English plant collector.

Deaths

• May 17 – Leopold Auenbrugger (born 1722), Austrian physician.
• August 18 – Matthew Boulton (born 1728), English mechanical engineer.
• October 11 – Meriwether Lewis (born 1774), American explorer.
• December 16 – Antoine François, comte de Fourcroy (born 1755), French chemist.
• December 29 – Thomas Barker (born 1722), English meteorologist.