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🔗 Time 🔗 Moon

A blue moon is an additional full moon that appears in a subdivision of a year: either the third of four full moons in a season, or a second full moon in a month of the common calendar.

The phrase in modern usage has nothing to do with the actual color of the Moon, although a visually blue Moon (the Moon appearing with a bluish tinge) may occur under certain atmospheric conditions – for instance, if volcanic eruptions or fires release particles in the atmosphere of just the right size to preferentially scatter red light.

🔗 Mathematics

The Ulam spiral or prime spiral is a graphical depiction of the set of prime numbers, devised by mathematician Stanisław Ulam in 1963 and popularized in Martin Gardner's Mathematical Games column in Scientific American a short time later. It is constructed by writing the positive integers in a square spiral and specially marking the prime numbers.

Ulam and Gardner emphasized the striking appearance in the spiral of prominent diagonal, horizontal, and vertical lines containing large numbers of primes. Both Ulam and Gardner noted that the existence of such prominent lines is not unexpected, as lines in the spiral correspond to quadratic polynomials, and certain such polynomials, such as Euler's prime-generating polynomial x² − x + 41, are believed to produce a high density of prime numbers. Nevertheless, the Ulam spiral is connected with major unsolved problems in number theory such as Landau's problems. In particular, no quadratic polynomial has ever been proved to generate infinitely many primes, much less to have a high asymptotic density of them, although there is a well-supported conjecture as to what that asymptotic density should be.

In 1932, more than thirty years prior to Ulam's discovery, the herpetologist Laurence Klauber constructed a triangular, non-spiral array containing vertical and diagonal lines exhibiting a similar concentration of prime numbers. Like Ulam, Klauber noted the connection with prime-generating polynomials, such as Euler's.

🔗 Military history 🔗 Military history/World War II 🔗 Scottish Islands

Operation Vegetarian was a British military plan in 1942 to disseminate linseed cakes infected with anthrax spores onto the fields of Germany. These cakes would have been eaten by the cattle, which would then be consumed by the civilian population, causing the deaths of millions of German citizens. Furthermore, it would have wiped out the majority of Germany's cattle, creating a massive food shortage for the rest of the population that remained uninfected. Preparations were not complete until early 1944. Operation Vegetarian was only to be used in the event of a German anthrax attack on the United Kingdom.

The cakes themselves were tested on Gruinard Island, just off the coast of Scotland. Because of the widespread contamination from the anthrax spores, the land remained quarantined until 1990. The five million cakes made to be disseminated in Germany were eventually destroyed in an incinerator shortly after the end of World War II.

In his novel The Impossible Dead (2011), author Ian Rankin mentions the clandestine events surrounding the removal of contaminated soils from Guinard Island by a protest group, the Dark Harvest Commando, and the island's removal from maps by the British Government. The island also features as the principal setting for the 1985 novel El año de gracia, by Cristina Fernández Cubas, in which the protagonist spends a winter shipwrecked on the island.

🔗 Biography 🔗 Aviation 🔗 Biography/science and academia 🔗 Aviation/aerospace biography 🔗 Former countries 🔗 Former countries/Ottoman Empire

Lagâri Hasan Çelebi was an Ottoman aviator who, according to the account written by traveller Evliya Çelebi, made a successful crewed rocket flight.

🔗 Mathematics 🔗 Systems 🔗 Systems/Chaos theory

Fractal compression is a lossy compression method for digital images, based on fractals. The method is best suited for textures and natural images, relying on the fact that parts of an image often resemble other parts of the same image. Fractal algorithms convert these parts into mathematical data called "fractal codes" which are used to recreate the encoded image.

🔗 Languages 🔗 Constructed languages 🔗 Constructed languages/Esperanto

Esperanto () is the most widely spoken constructed international auxiliary language. It was created by Polish ophthalmologist L. L. Zamenhof in 1887, when he published a book detailing the language, The International Language whose editions in Russian, Polish, German, French and English, under the pseudonym “Doktoro Esperanto” together constitute the “original edition”, usually referred to by Esperantists as “La Unua Libro” (“The First Book”). The word esperanto translates into English as "one who hopes".

Zamenhof's goal was to create an easy and flexible language that would serve as a universal second language to foster world peace and international understanding, and to build a community of speakers, as he believed that one could not have a language without such a community.

His original title for the language was simply "the international language" (lingvo internacia), but early speakers grew fond of the name Esperanto and began to use it as the name for the language just two years after its creation; the name quickly gained prominence and has been used as an official name ever since.

In 1905, Zamenhof published Fundamento de Esperanto as a definitive guide to the language. Later that year, French Esperantists organized with his participation the first World Esperanto Congress, an ongoing annual conference, in Boulogne-sur-Mer, France. The first congress ratified the Declaration of Boulogne, which established several foundational premises for the Esperanto movement; one of its pronouncements is that Fundamento de Esperanto is the only obligatory authority over the language; another is that the Esperanto movement is exclusively a linguistic movement and that no further meaning can ever be ascribed to it. Zamenhof also proposed to the first congress that an independent body of linguistic scholars should steward the future evolution of Esperanto, foreshadowing the founding of the Akademio de Esperanto (in part modeled after the Académie française), which was established soon thereafter. Since 1905, the congress has been held in a different country every year, with the exceptions of those years during the World Wars. In 1908, a group of young Esperanto speakers led by the Swiss Hector Hodler established the Universal Esperanto Association in order to provide a central organization for the global Esperanto community.

Esperanto grew throughout the 20th century, both as a language and as a linguistic community. Despite speakers facing persecution in regimes such as Nazi Germany and the Soviet Union under Stalin, Esperanto speakers continued to establish organizations and publish periodicals tailored to specific regions and interests. In 1954, the United Nations granted official support to Esperanto as an international auxiliary language in the Montevideo Resolution. Several writers have contributed to the growing body of Esperanto literature, including William Auld, who received the first nomination for the Nobel Prize in Literature for a literary work in Esperanto in 1999, followed by two more, in 2004 and 2006. Those writing in Esperanto are also officially represented in PEN International, the worldwide writers association, through Esperanto PEN Centro.

The development of Esperanto has continued unabated into the 21st century. The advent of the Internet has had a significant impact on the language, as learning it has become increasingly accessible on platforms such as Duolingo, and as speakers have increasingly networked on platforms such as Amikumu. With approximately two million speakers, a small portion of whom are even native speakers, it is the most widely spoken constructed language in the world. Although no country has adopted Esperanto officially, Esperantujo is the name given to the collection of places where it is spoken, and the language is widely employed in world travel, correspondence, cultural exchange, conventions, literature, language instruction, television, and radio. Some people have chosen to learn Esperanto for its purported help in third language acquisition, like Latin.

While many of its advocates continue to hope for the day that Esperanto becomes officially recognized as the international auxiliary language, an increasing number have stopped focusing on this goal and instead view the Esperanto community as a "stateless diasporic linguistic minority" based on freedom of association, with a culture worthy of preservation, based solely on its own merit.

🔗 Computing 🔗 Spaceflight 🔗 Computing/Software

DRAKON is an algorithmic visual programming and modeling language developed within the Buran space project following ergonomic design principles. The language provides a uniform way to represent flowcharts of any complexity that are easy to read and understand.

The DRAKON Editor, which was released in September 2011, is an implementation of the language available in the public domain. It can be used for creating documentation, or for creating visual programs that can be converted to source code in other languages.

Unlike UML's philosophy, DRAKON's language philosophy is based on being augmented if needed, by using a hybrid language, which can be illustrated as "incrustating code snippets from text language used into shape DRAKON requires". This way, DRAKON always remains a simple visual language that can be used as an augmentation for a programmer who is interested in making their own project code easier to support or other long-term needs for example improving the ergonomics of the coding process or to making code easier to review and understand.

The name DRAKON is the Russian acronym for "Дружелюбный Русский Алгоритмический [язык], Который Обеспечивает Наглядность", which translates to "Friendly Russian algorithmic [language] that illustrates (or provides clarity)". The word "наглядность" (pronounced approximately as "naa-glya-dno-st-th") refers to a concept or idea being easy to imagine and understand, and may be translated as "clarity".

The DRAKON language can be used both as a modelling/"markup" language (which is considered a standalone "pure DRAKON" program) and as a programming language (as part of a hybrid language).

Integration of a stricter, "academic", variant of a markup language into programming, such as provided by DRAKON, adds syntactic sugar allowing users of different programming languages to comprehend each other's contributions to the overall project and even provide commentary if needed.

🔗 Mathematics 🔗 Statistics

In mathematics, the theory of optimal stopping or early stopping is concerned with the problem of choosing a time to take a particular action, in order to maximise an expected reward or minimise an expected cost. Optimal stopping problems can be found in areas of statistics, economics, and mathematical finance (related to the pricing of American options). A key example of an optimal stopping problem is the secretary problem. Optimal stopping problems can often be written in the form of a Bellman equation, and are therefore often solved using dynamic programming.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Italy 🔗 Architecture 🔗 Military history/Early Modern warfare 🔗 Military history/Maritime warfare 🔗 Ships 🔗 Military history/Medieval warfare 🔗 Industrial design 🔗 Military history/Italian military history 🔗 Former countries 🔗 Military history/European military history 🔗 Former countries/Italian historical states

The Venetian Arsenal (Italian: Arsenale di Venezia) is a complex of former shipyards and armories clustered together in the city of Venice in northern Italy. Owned by the state, the Arsenal was responsible for the bulk of the Venetian republic's naval power from the late Middle Ages to the early modern period. It was "one of the earliest large-scale industrial enterprises in history".