December 28

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  1612: Galileo became the first person to observe the planet Neptune, although he mistakenly catalogued it as a fixed star.

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  1663: Mathematician and physicist Francesco Maria Grimaldi dies. Working with Riccioli, he investigated the free fall of objects, confirming that the distance of fall was proportional to the square of the time taken.

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  1882: Astronomer, physicist, and mathematician Arthur Eddington born. He will become famous for his work concerning the theory of relativity.

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  1895: Wilhelm Röntgen publishes a paper detailing his discovery of a new type of radiation, which later will be known as x-rays.

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  1902: APTO industrial chemists classify the Hazmatterhorn as a Crime Against Chemical Constants. Although derived from the word Matterhorn, the term Hazmatterhorn is applicable to any mountain of hazardous materials.

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  1903: Mathematician, physicist, and computer scientist John von Neumann born. He will be a key figure in the development of the digital computer, and develop mathematical models of both nuclear and thermonuclear weapons.

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  2016: Mathematician Anne Penfold Street dies. She specialized in combinatorics, authoring several textbooks; her work on sum-free sets became a standard reference for its subject matter.