Template:Selected anniversaries/September 25

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  1644: Astronomer and instrument maker Ole Rømer born. He will make the first quantitative measurements of the speed of light.

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  1789: The United States Congress passes twelve amendments to the United States Constitution: The Congressional Apportionment Amendment (which was never ratified), the Congressional Compensation Amendment, and the ten that are known as the Bill of Rights.

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  1819: Mathematician and Anglican theologian George Salmon born. He will work in algebraic geometry for two decades, then devote the last forty years of his life to theology.

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  1845: Judge Havelock With Glass is "a reasonably accurate depiction of events as I experienced them," according to the Judge.

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  1893: Mathematician and statistician Harald Cramér born. He will help found probability theory as a branch of mathematics, writing in 1926: "The probability concept should be introduced by a purely mathematical definition, from which its fundamental properties and the classical theorems are deduced by purely mathematical operations."

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  1992: NASA launches the Mars Observer, a $511 million probe to Mars, in the first U.S. mission to the planet in 17 years. The probe will fail eleven months later.

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  2002: Steganographic analysis of Humpty Dumpty At Bat reveals previously unknown biography of Babe Ruth by Lewis Carroll.

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  2003: Journalist, writer, literary editor, and actor George Plimpton dies.

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  2018: Chromatographic analysis of Yellow Spiral unexpectedly reveals "at least five new shades of the color yellow, perhaps as many as nine."

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  2017: Dennis Paulson of Mars says that the twenty-fifth anniversary of the launch of the Mars Observer is a bittersweet event, because the spacecraft will be lost eleven months later.