1821 in science

The year 1821 in science and technology included many events, some of which are listed here.

Astronomy

• Comet Encke is the second comet to be discovered to have a periodic orbit, after Comet Halley
• Alexis Bouvard detects irregularities in the orbit of Uranus

Exploration

• William Edward Parry starts his second voyage to find the Northwest Passage

Geology

• Ignatz Venetz proposes his ice age theory
• Pierre Berthier discovers bauxite
• Mary Anning finds the first ever plesiosaur fossil at Lyme Regis

Mathematics

• Augustin Louis Cauchy gives the first complete presentation of calculus using limits

Paleontology

• William Buckland finds the remains of a hyenas' den in Yorkshire, containing the bones of lions, elephants and rhinoceros

Physics

• Michael Faraday discovers electromagnetic rotation
• T. J. Seebeck discovers the thermoelectric effect
• Augustin Fresnel shows that light is made up of a traverse wave motion

Awards

• Copley Medal: Edward Sabine; John Herschel

Births

• May 16 - Pafnuty Chebyshev, mathematician († 1894)
• August 16 - Arthur Cayley, mathematician († 1895)
• August 31 - Hermann von Helmholtz, physicist († 1894)
• October 13 - Rudolf Virchow, biologist († 1902)
• November 18 - Franz Bronnow, astronomer († 1891)

Deaths

• April 20 - Franz Karl Achard, chemist (* 1753)