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🔗 Mathematics

Zero is an even number. In other words, its parity—the quality of an integer being even or odd—is even. This can be easily verified based on the definition of "even": it is an integer multiple of 2, specifically 0 × 2. As a result, zero shares all the properties that characterize even numbers: for example, 0 is neighbored on both sides by odd numbers, any decimal integer has the same parity as its last digit—so, since 10 is even 0 will be even, and if y is even then y + x has the same parity as x—and x and 0 + x always have the same parity.

Zero also fits into the patterns formed by other even numbers. The parity rules of arithmetic, such as even − even = even, require 0 to be even. Zero is the additive identity element of the group of even integers, and it is the starting case from which other even natural numbers are recursively defined. Applications of this recursion from graph theory to computational geometry rely on zero being even. Not only is 0 divisible by 2, it is divisible by every power of 2, which is relevant to the binary numeral system used by computers. In this sense, 0 is the "most even" number of all.

Among the general public, the parity of zero can be a source of confusion. In reaction time experiments, most people are slower to identify 0 as even than 2, 4, 6, or 8. Some students of mathematics—and some teachers—think that zero is odd, or both even and odd, or neither. Researchers in mathematics education propose that these misconceptions can become learning opportunities. Studying equalities like 0 × 2 = 0 can address students' doubts about calling 0 a number and using it in arithmetic. Class discussions can lead students to appreciate the basic principles of mathematical reasoning, such as the importance of definitions. Evaluating the parity of this exceptional number is an early example of a pervasive theme in mathematics: the abstraction of a familiar concept to an unfamiliar setting.

🔗 Music/Music genres

Black MIDI is a music genre consisting of compositions that use MIDI files to create a song or a remix containing a large number of notes, typically in the thousands, millions, billions, or even trillions. People who make black MIDIs are known as blackers. However, there are no specific criteria of what is considered "black"; as a result, pinpointing the exact origin of black MIDI is impossible.

🔗 Computing 🔗 Animation

Animated Portable Network Graphics (APNG) is a file format which extends the Portable Network Graphics (PNG) specification to permit animated images that work similarly to animated GIF files, while supporting 24 or 48-bit images and full alpha transparency not available for GIFs. It also retains backward compatibility with non-animated PNG files.

The first frame of an APNG file is stored as a normal PNG stream, so most standard PNG decoders are able to display the first frame of an APNG file. The frame speed data and extra animation frames are stored in extra chunks (as provided for by the original PNG specification). APNG competed with Multiple-image Network Graphics (MNG), a comprehensive format for bitmapped animations which was created by the same team as PNG and is obsolete. APNG's advantage was the smaller library size and compatibility with older PNG implementations.

🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Aviation/aircraft 🔗 Smithsonian Institution-related 🔗 Smithsonian Institution

The Goodyear Inflatoplane was an inflatable experimental aircraft made by the Goodyear Aircraft Company, a subsidiary of Goodyear Tire and Rubber Company, well known for the Goodyear blimp. Although it seemed an improbable project, the finished aircraft proved to be capable of meeting its design objectives, although orders were never forthcoming from the military. A total of 12 prototypes were built between 1956 and 1959, and testing continued until 1972, when the project was finally cancelled.

🔗 Literature 🔗 Education 🔗 Reference works

Commonplace books (or commonplaces) are a way to compile knowledge, usually by writing information into books. They have been kept from antiquity, and were kept particularly during the Renaissance and in the nineteenth century. Such books are essentially scrapbooks filled with items of every kind: recipes, quotes, letters, poems, tables of weights and measures, proverbs, prayers, legal formulas. Commonplaces are used by readers, writers, students, and scholars as an aid for remembering useful concepts or facts. Each one is unique to its creator's particular interests but they almost always include passages found in other texts, sometimes accompanied by the compiler's responses. They became significant in Early Modern Europe.

"Commonplace" is a translation of the Latin term locus communis (from Greek tópos koinós, see literary topos) which means "a general or common topic", such as a statement of proverbial wisdom. In this original sense, commonplace books were collections of such sayings, such as John Milton's example. Scholars now understand them to include manuscripts in which an individual collects material which have a common theme, such as ethics, or exploring several themes in one volume. Commonplace books are private collections of information, but they are not diaries or travelogues.

In 1685 the English Enlightenment philosopher John Locke wrote a treatise in French on commonplace books, translated into English in 1706 as A New Method of Making Common-Place-Books, "in which techniques for entering proverbs, quotations, ideas, speeches were formulated. Locke gave specific advice on how to arrange material by subject and category, using such key topics as love, politics, or religion. Commonplace books, it must be stressed, are not journals, which are chronological and introspective."

By the early eighteenth century they had become an information management device in which a note-taker stored quotations, observations and definitions. They were used in private households to collate ethical or informative texts, sometimes alongside recipes or medical formulae. For women, who were excluded from formal higher education, the commonplace book could be a repository of intellectual references. The gentlewoman Elizabeth Lyttelton kept one from the 1670s to 1713 and a typical example was published by Mrs Anna Jameson in 1855, including headings such as Ethical Fragments; Theological; Literature and Art. Commonplace books were used by scientists and other thinkers in the same way that a database might now be used: Carl Linnaeus, for instance, used commonplacing techniques to invent and arrange the nomenclature of his Systema Naturae (which is the basis for the system used by scientists today). The commonplace book was often a lifelong habit: for example the English-Australian artist Georgina McCrae kept a commonplace book from 1828-1865.

🔗 Death 🔗 Greece 🔗 Paranormal

The term Drosoulites (Greek: Δροσουλίτες) refers to a long procession of visions, seen by residents around Frangokastello castle in Sfakia region of Crete (Greece). The phenomenon is rumored to be visible every year, on the anniversary of the Battle of Frangokastello or even in early June near a small village in southern Crete.

The visions, as described by witnesses, consist of a group of human-like shadows dressed in black, walking or riding, armed with weapons, moving from the monastery of Agios Charalambos and advancing towards the old fort, Frangokastello, a 14th-century Venetian fortification. Legend has it that this group of people are Greek fighters that died during the Battle of Frangokastello (17 May 1828) and since then they appear as supernatural beings in the area.

The ghost army is led by Hatzimichalis Dalianis, from Delvinaki in Epirus, the chief of the Greek men, 350 of whom were lost, in the battle. The army took refuge in the fort during the Greek War of Independence against the Turks, where they were killed after a seven-day siege.

The local people named them Drosoulites ("dew shadows") due to the time of day that the phenomenon takes place. The phenomenon is observed when the sea is calm and the atmosphere is moist and before the sun rises too high in the sky. It usually lasts about 10 minutes.

The shadows are visible from the valley at a distance of 1000 m. Many have tried to explain the phenomenon scientifically, and at one time it was explained as a mirage from the coast of North Africa, but still there is no accepted consensus. On the other hand, another, occult, interpretation implies the existence of a psychic phenomenon, clairvoyance, seen in some countries like Britain and Germany, also regarding ghost armies. The appearance of the Drosoulites is documented over the ages. In 1890 a transient Turkish army took the images for rebels and fled away. Even during the Second World War, a German patrol is said to have opened fire on the visions.

🔗 Computing 🔗 Mathematics 🔗 Computing/Networking

In mathematics, the Cheeger constant (also Cheeger number or isoperimetric number) of a graph is a numerical measure of whether or not a graph has a "bottleneck". The Cheeger constant as a measure of "bottleneckedness" is of great interest in many areas: for example, constructing well-connected networks of computers, card shuffling. The graph theoretical notion originated after the Cheeger isoperimetric constant of a compact Riemannian manifold.

The Cheeger constant is named after the mathematician Jeff Cheeger.

🔗 Greece 🔗 Middle Ages 🔗 Middle Ages/History 🔗 Greece/Byzantine world 🔗 Textile Arts

In the mid-6th century CE, two monks, with the support of the Byzantine emperor Justinian I, acquired and smuggled living silkworms into the Byzantine Empire, which led to the establishment of an indigenous Byzantine silk industry that long held a silk monopoly in Europe.

🔗 Australia 🔗 Australia/Melbourne 🔗 Australia/Australian crime 🔗 Visual arts

The theft of The Weeping Woman from the National Gallery of Victoria took place on 2 August 1986 in Melbourne, Victoria, Australia. The stolen work was one of a series of paintings by Pablo Picasso all known as The Weeping Woman and had been purchased by the gallery for A$1.6 million in 1985—at the time the highest price paid by an Australian art gallery for an artwork. A group calling itself "Australian Cultural Terrorists" claimed responsibility, making a number of demands (and insults) in letters to the then-Victorian Minister for the Arts, Race Mathews. The demands included increases to funding for the arts; threats were made that the painting would be destroyed. After an anonymous tip-off to police, the painting was found undamaged in a locker at Spencer Street railway station on 19 August 1986. The theft still remains unsolved.

🔗 France 🔗 Military history 🔗 Architecture 🔗 Military history/Fortifications 🔗 Military history/French military history 🔗 Archaeology 🔗 Military history/Medieval warfare 🔗 Metalworking 🔗 Military history/European military history 🔗 Woodworking

Guédelon Castle (Château de Guédelon) is a castle currently under construction near Treigny, France. The castle is the focus of an experimental archaeology project aimed at recreating a 13th-century castle and its environment using period technique, dress, and material.

In order to fully investigate the technology required in the past, the project is using only period construction techniques, tools, and costumes. Materials, including wood and stone, are all obtained locally. Jacques Moulin, chief architect for the project, designed the castle according to the architectural model developed during the 12th and 13th centuries by Philip II of France.

Construction started in 1997 under Michel Guyot, owner of Château de Saint-Fargeau, a castle in Saint-Fargeau 13 kilometres away. The site was chosen according to the availability of construction materials: an abandoned stone quarry, in a large forest, with a nearby pond. The site is in a rural woodland area and the nearest town is Saint-Sauveur-en-Puisaye, about 5 kilometres (3.1 mi) to the northeast.