Discovery of nuclear fission

Discovery of nuclear fission.
Nuclear fission was discovered in December 1938 by physicists Lise Meitner and Otto Frisch, and chemists Otto Hahn and Fritz Strassmann. Fission is a nuclear reaction and process of radioactive decay in which the nucleus of an atom splits into two or more smaller, lighter nuclei. The fission process releases a very large amount of energy. The discovery that a nuclear chain reaction was possible led to the development of nuclear power and nuclear weapons. Hahn and Strassmann bombarded uranium with slow neutrons, and discovered that barium had been produced (illustration pictured). Meitner and her nephew Frisch theorised, and then proved, that the uranium nucleus had been split, and published their findings in Nature. Meitner calculated that the energy released by each disintegration was approximately 200 megaelectronvolts, and Frisch observed this. By analogy with the division of biological cells, Frisch named the process "fission". Hahn was awarded the 1944 Nobel Prize in Chemistry for the discovery.

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The Thankful Poor

The Thankful Poor.
The Thankful Poor is an 1894 painting by the African-American painter Henry Ossawa Tanner. It is a genre painting of two African Americans praying at a table and shares themes with Tanner's other works like The Banjo Lesson (1893). The painting is considered a milestone in African-American art, notably for its countering of racial stereotypes by portraying African-American culture in a dignified manner. This depiction was influenced by Tanner's father and the African Methodist Episcopal Church. Despite its popularity with critics, The Thankful Poor was Tanner's last African-American genre work before he began to focus on biblical scenes. After remaining hidden for years, the painting was discovered in a storage closet of the Pennsylvania School for the Deaf in 1970, before being purchased by Camille and Bill Cosby in 1981 for their private collection. In 2020, the painting was sold by the Cosbys to Art Bridges, a foundation created by Alice Walton for loaning artwork.

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Pisco sour

Pisco sour.
A pisco sour is a cocktail typical of South American cuisine. The drink's name is a combination of the word pisco, which is its base liquor, and the term sour, in reference to sour citrus juice and sweetener components. Chile and Peru both claim the pisco sour as their national drink, and each asserts exclusive ownership of both pisco and the cocktail. The Peruvian pisco sour uses Peruvian pisco as the base liquor and adds Key lime (or lemon) juice, syrup, ice, egg white, and Angostura bitters. The Chilean version is similar, but uses Chilean pisco and Pica lemon, and excludes the bitters and egg white. The cocktail was invented by Victor Vaughen Morris, an American bartender working in Peru in the early 1920s. In Chile, the invention of the drink is attributed to Elliot Stubb, an English ship steward, at a bar in the port city of Iquique in 1872, although the source for this attributed the invention of the whiskey sour to Stubb, not the pisco sour. The two kinds of pisco and the two variations in the style of preparing the pisco sour are distinct in both production and taste, and the pisco sour has become a significant and oft-debated topic of Latin American popular culture.

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Rock martin

Rock martin.
The rock martin (Ptyonoprogne fuligula) is a small swallow that is resident in central and southern Africa. It breeds in the mountains, and at lower levels in rocky areas and towns. It has mainly brown plumage and white "windows" on the spread tail. Its call is a soft twitter. The sexes are similar in appearance. The martin hunts along cliff faces for flying insects. It breeds under cliff overhangs or on man-made structures using mud pellets to build a bowl or half-bowl nest with a soft lining. The bird is a solitary breeder, but small groups may nest close together in suitable locations. A typical clutch has two to three eggs, which are white with brown and grey blotches. Both adults incubate the eggs for 16–19 days and feed the chicks. Fledging takes another 22–24 days. The small martin is caught in flight by several falcons, such as hobbies, but it faces no major threats. Because of its extensive range and large stable population, it is assessed as a least-concern species on the IUCN Red List. (This article is part of a featured topic: Crag martins.)