1991 in science

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The year 1991 in science and technology involved many significant events, some listed below.

Astronomy and space exploration

May 18 – Helen Sharman becomes the first British person in space, flying with the Soyuz TM-12 mission.^[1] As of 2011 she is the only British astronaut.
October 29 – The Galileo probe becomes the first spacecraft to visit an asteroid (951 Gaspra).
Asteroid 6859 Datemasamune is discovered by Masahiro Koishikawa.
11514 Tsunenaga is discovered.
There are four lunar eclipses: three penumbral on January 30, July 26, and June 27, and one minor partial lunar eclipse on December 21.
There are two solar eclipses, one annular eclipse on January 15, and a very long total eclipse on July 11, lasting 6 minutes and 53 seconds.

Carbon nanotubes discovered in the insoluble material of arc-burned graphite rods by Sumio Iijima of NEC.^[2]^[3]

February 26 – Tim Berners-Lee introduces WorldWideWeb, the first web browser, and a WYSIWYG HTML editor.
June 5 – Phil Zimmermann posts the first Pretty Good Privacy (PGP) data encryption program.^[4]
June 23 – The video game Sonic the Hedgehog is first released, propelling the Sega Genesis 16-bit console into mass popularity.
August 6 – The first website goes online at CERN.^[5]^[6]^[7]^[8]
Pei-Yuan Wei releases the Web browser ViolaWWW 0.8.

Alan Hildebrand and others provide support for the Alvarez hypothesis for the Cretaceous–Paleogene extinction event by proposing the Chicxulub crater in the Yucatán Peninsula of Mexico as the impact site for a large asteroid 66 million years ago.^[9]^[10]^[11]

July – English physicist Philip Candelas and colleagues show that mirror symmetry could be used to solve problems in enumerative geometry.^[12]
Qiudong Wang produces a global solution to the n-body problem.^[13]

The first open-access scientific online archive, arXiv, is begun as a preprint service for physicists, initiated by Paul Ginsparg.

January 30 – John Bardeen (b. 1908), American physicist, co-inventor of the transistor and twice winner of the Nobel Prize in Physics.
February 6 – Salvador Luria (b. 1912), Italian-born biologist, co-winner of the Nobel Prize in Physiology or Medicine.
February 23 – Sir Charles Illingworth (b. 1899), British surgeon.
March 1 – Edwin H. Land (b. 1909), American inventor of the Land Camera.
June 2 – Mary Loveless (b. 1899), American immunologist.
June 5 – Min Chueh Chang (b. 1908), Chinese American embryologist.
December 2 – Anne Beloff-Chain (b. 1921), British biochemist.