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 (d. 1894), mathematician.
• August 16 – Arthur Cayley (d. 1895), mathematician.
• August 31 – Hermann von Helmholtz (d. 1894), physicist.
• October 13 – Rudolf Virchow (d. 1902), biologist.
• November 18 – Franz Bronnow (d. 1891), astronomer.

Deaths

• April 20 – Franz Karl Achard (b. 1753), chemist.