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🔗 Mathematics

Gabriel's horn (also called Torricelli's trumpet) is a geometric figure which has infinite surface area but finite volume. The name refers to the Abrahamic tradition identifying the archangel Gabriel as the angel who blows the horn to announce Judgment Day, associating the divine, or infinite, with the finite. The properties of this figure were first studied by Italian physicist and mathematician Evangelista Torricelli in the 17th century.

🔗 Mathematics 🔗 Germany 🔗 Germany/Prussia

The Seven Bridges of Königsberg is a historically notable problem in mathematics. Its negative resolution by Leonhard Euler in 1736 laid the foundations of graph theory and prefigured the idea of topology.

The city of Königsberg in Prussia (now Kaliningrad, Russia) was set on both sides of the Pregel River, and included two large islands—Kneiphof and Lomse—which were connected to each other, or to the two mainland portions of the city, by seven bridges. The problem was to devise a walk through the city that would cross each of those bridges once and only once.

By way of specifying the logical task unambiguously, solutions involving either

1. reaching an island or mainland bank other than via one of the bridges, or
2. accessing any bridge without crossing to its other end

are explicitly unacceptable.

Euler proved that the problem has no solution. The difficulty he faced was the development of a suitable technique of analysis, and of subsequent tests that established this assertion with mathematical rigor.

🔗 Color

Pantone 448 C, also referred to as "the ugliest colour in the world", is a colour in the Pantone colour system. Described as a "drab dark brown", it was selected in 2016 as the colour for plain tobacco and cigarette packaging in Australia, after market researchers determined that it was the least attractive colour. The Australian Department of Health initially referred to the colour as "olive green", but the name was changed after concerns were expressed by the Australian Olive Association.

Since 2016, the same colour has also been used for plain cigarette packaging in France, the United Kingdom, Israel, Norway, New Zealand, Slovenia, Saudi Arabia, and Turkey.

The colour has also been widely but erroneously reported as being known as "opaque couché"; in fact this is simply French for "layered opaque", in reference to being used on coated paper. The confusion appears to have arisen because "PANTONE opaque couché" is the French name of a swatch library (palette) used in Adobe Illustrator containing this colour and intended for printing in solid ink colours on coated paper; in English this library is known as "PANTONE solid coated".

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Cold War

Blue Peacock, renamed from Blue Bunny and originally Brown Bunny, was a British tactical nuclear weapon project in the 1950s.

The project's goal was to store a number of ten-kiloton nuclear mines in Germany, to be placed on the North German Plain and, in the event of Soviet invasion from the east, detonated by wire or an eight-day timer to:

... not only destroy facilities and installations over a large area, but ... deny occupation of the area to an enemy for an appreciable time due to contamination ...