Wikipedia:Main Page history/2014 September 23

Fluorine is an extremely reactive chemical element with atomic number 9 (pictured in a liquid form at a cryogenic temperature). A highly toxic pale yellow gas at standard conditions, it was first described in 1529 as its principal source fluorite, a mineral added as a flux for smelting, and named after the Latin verb fluo meaning "flow". As the lightest halogen and most electronegative element, it is difficult to separate from its compounds, and several early experimenters died or were injured. The process employed for its modern production—low-temperature electrolysis—remains the same as that used by Henri Moissan in 1886 to achieve its first isolation. The high costs of refining fluorine gas lead most commercial uses, such as aluminium refining, insulation and refrigeration, to use its compounds; uranium enrichment is the free element's largest application. Fluorine is a part of some pharmaceuticals and appears as the fluoride ion in toothpaste, but has no known metabolic role in mammals; a few plants possess fluorine-containing poisons to deter herbivores. Fluorocarbon gases are usually potent greenhouse gases and organofluorine compounds persist in the environment. (Full article...)

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From Wikipedia's new and recently improved content:

• ... that the trans woman activist Miss Major (pictured) was meeting with her girlfriend at the Stonewall Inn during the police raid that precipitated the Stonewall riot?
• ... that Patagosaurus is a genus of sauropod dinosaur from Patagonia that is known from an almost complete skeleton and partial skull?
• ... that Darol Froman was the scientific director of the Operation Sandstone nuclear tests at Enewetak Atoll in 1948?
• ... that little is known of the breeding habits of the fiery-shouldered parakeet?
• ... that the Australian plant Lomatia arborescens has large serrated leaves when it grows in a sheltered spot and small entire-margined leaves in an exposed location?
• ... that Robert Pitcairn was only fifteen when he discovered the island which is now named after him?
• ... that, after playing a detective, the social worker LV Wijnhamer became a suspect?

• NASA's probe MAVEN enters orbit around Mars to study the planet's atmosphere.
• The National Party, led by John Key (pictured), win a majority in the New Zealand general election.
• Chinese e-commerce company Alibaba Group raises US$25 billion on the New York Stock Exchange, in the largest ever initial public offering.
• Scotland votes against independence from the United Kingdom.
• In cycling, Jens Voigt sets a new hour record, riding more than 51 kilometres (31.7 mi) in an hour.
• The FijiFirst Party, led by Frank Bainimarama, win a majority in the Fijian general election.

Ongoing:

Ebola outbreak –

Islamic State of Iraq and the Levant

September 23: September Equinox (02:29 UTC, 2014); National Day in Saudi Arabia (1932); Celebrate Bisexuality Day

• 1123 – Pope Calixtus II and Holy Roman Emperor Henry V agreed to the Concordat of Worms to put an end to the Investiture Controversy.
• 1780 – American Revolutionary War: British officer John André was captured by Patriot forces, thereby revealing a plot by Continental Army General Benedict Arnold (pictured) to hand over West Point, New York.
• 1803 – Maratha troops were beaten by British forces at the Battle of Assaye, one of the decisive battles of the Second Anglo-Maratha War.
• 1932 – The Kingdom of Nejd and Hejaz merged with Al-Hasa and Qatif to form the Kingdom of Saudi Arabia, with Ibn Saud as the first monarch and Riyadh as the capital city.
• 1983 – A bomb placed by the Abu Nidal organisation destroyed Gulf Air Flight 771, flying from Karachi, Pakistan, to Abu Dhabi, UAE, killing all 110 people aboard.

More anniversaries: September 22 – September 23 – September 24

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The radian is the standard unit of angular measure, used in many areas of mathematics. An angle's measurement in radians is numerically equal to the length of a corresponding arc of a unit circle, so one radian is just under 57.3 degrees (when the arc length is equal to the radius); a full circle corresponds to an angle of 2π radians. In the SI, the radian has the symbol "rad"; it was a supplementary unit until that category was abolished in 1995, and is now considered a derived unit.

Diagram: Lucas V. Barbosa