The steradian or square radian is the SI unit of solid angle. It is used in three-dimensional geometry, is analogous to the radian, which quantifies planar angles. Whereas an angle in radians, projected onto a circle, gives a length on the circumference, a solid angle in steradians, projected onto a sphere, gives an area on the surface; the name is derived from the Greek στερεός stereos'solid' + radian. The steradian, like the radian, is a dimensionless unit, the quotient of the area subtended and the square of its distance from the center. Both the numerator and denominator of this ratio have dimension length squared, it is useful, however, to distinguish between dimensionless quantities of a different nature, so the symbol "sr" is used to indicate a solid angle. For example, radiant intensity can be measured in watts per steradian; the steradian was an SI supplementary unit, but this category was abolished in 1995 and the steradian is now considered an SI derived unit. A steradian can be defined as the solid angle subtended at the center of a unit sphere by a unit area on its surface.

For a general sphere of radius r, any portion of its surface with area A = r2 subtends one steradian at its center. The solid angle is related to the area it cuts out of a sphere: Ω = A r 2 s r = 2 π h r s r where A is the surface area of the spherical cap, 2 π r h, r is the radius of the sphere, sr is the unit, steradian; because the surface area A of a sphere is 4πr2, the definition implies that a sphere subtends 4π steradians at its center. By the same argument, the maximum solid angle that can be subtended at any point is 4π sr. If A = r2, it corresponds to the area of a spherical cap and the relationship h/r = 1/2π holds. Therefore, in this case, one steradian corresponds to the plane angle of the cross-section of a simple cone subtending the plane angle 2θ, with θ given by: θ = arccos ⁡ = arccos ⁡ = arccos ⁡ ≈ 0.572 rad, or 32.77 ∘. This angle corresponds to the plane aperture angle of 2θ ≈ 1.144 rad or 65.54°. A steradian is equal to the spherical area of a polygon having an angle excess of 1 radian, to 1/4π of a complete sphere, or to 2 ≈ 3282.80635 square degrees.

The solid angle of a cone whose cross-section subtends the angle 2θ is: Ω = 2 π s r. Millisteradians and microsteradians are used to describe light and particle beams. Other multiples are used. N-sphere Square degree Spat List of constellations by area Media related to Steradian at Wikimedia Commons

Knight (DC Comics)

The Knight is the name of three fictional comic book superheroes who are properties of DC Comics. Percival Sheldrake debuted as the Knight in Batman #62, was created by Bill Finger and Dick Sprang. Cyril Sheldrake debuted as the Knight in JLA #26, was created by Grant Morrison and Howard Porter. Beryl Hutchinson first appeared as Squire in the same issue, became the Knight in Batman Incorporated v2 #09; the first Knight first appeared in Batman #62 in a story entitled "The Batman of England!" He is a British vigilante who models himself after the Knights of the Round Table, after Batman, including having a teenage sidekick, the Squire. He is Percy Sheldrake, Earl of Wordenshire, the Squire is his son Cyril. Instead of a Bat-Signal he is summoned by ringing the Wordenshire church bell; the Knight is a member of the Batmen of All Nations—also known as the Club of Heroes—an international team of superheroes whose careers were inspired by Batman's example. It is revealed that Percy had begun his heroic career as squire to the Shining Knight during World War II.

Percy was murdered by the villain Spring Heeled Jack and his son, the former squire assumed the mantle. The second Knight first appears in a group shot of the Ultramarine Corps at the end of JLA #26; the subsequent appearance of the Corps in JLA Classified establishes that he is Cyril Sheldrake, who inherited both the title of Earl and that of the Knight when his father was killed by his archenemy, Springheeled Jack. Worrying he wouldn't live up to his father's formidable reputation as a hero Cyril turned to drink and gambling losing Sheldrake castle at one point due to his debts, it was that a young girl named Beryl rescued him from the gutter and helped the knight clean up his act offering him a room and use of her garage as his Superhero HQ. Cyril repaid her kindness by training her to be his squire. Cyril has since excelled at his task as Britain's primary defender of the innocent and joined several international hero groups The Knight's current motorcycle is named Anastasia, after Dan Dare's spaceship, has a stylized horse's head.

Anastasia has a chemical tracking system built into her "nose". It is of tougher construction than a standard motorbike, surviving a head on jousting match with a Richard the Third clone suffering no significant damage, he employs a squadron of miniaturized Spitfires under his control. Not only can they be used offensively against a variety of enemies, they can see in various wavelengths and have been used to follow the trail of a serial killer, his armor as well as providing protection from attack contains a variety of visual scanners and communication devices in the visor. The armor is capable of moving independently of him an experiment to make the armor continue fighting when Cyril was unconscious resulted in it becoming self-aware and attacking. Squire handles the communications and computer side of things whilst his American man servant Hank Hackenbacker services and builds the bulk of his vehicles and machines as well as offering annoyingly sage advice when needed. Captain Cornwall and his son Cornwall Boy Rush Hour 1, 2 and 3 Milk Man The Fro The Distinguished Gentlemen Birthday Girl The Mechanic In Battle for the Cowl, The Knight, along with Squire, is a member of the Network, a group of heroes whom the Bat-Family trusted to assist them if the need arose.

Knight is seen assisting Dick Grayson in quelling the chaos in Gotham which erupted with the rumors of Batman's death. Knight appears in Batman and Robin #7-9, where Batman asks for his help in locating the last Lazarus Pit in order to bring Bruce Wayne back to life. Knight placed Batman's corpse in the Lazarus Pit before Grayson and Squire's arrival, he, along with Batwoman and Batman, is the first one to see the corpse of Batman returned to life. However, they soon discover that the corpse was in fact a clone of Batman, not Batman himself; this copy has a defect, making him impossible to control. Writer Paul Cornell has written a six-issue Knight and Squire limited series with artist Jimmy Broxton and cover artist Yanick Paquette; the first issue was published in October 2010. As shown in the limited series, the Knight is still based in Sheldrake Castle, Great Worden, equipped in a similar manner to the Batcave; the Knight's current motorcycle is named Anastasia, after Dan Dare's spaceship, has a stylized horse's head.

Anastasia has a chemical tracking system built into her "nose". It is of tougher construction than a standard motorbike, surviving a head on jousting match with a Richard the Third clone suffering no significant damage; the Knight is portrayed as something of an elder statesman to other British superheroes, including Captain Cornwall and Rush Hour I to III. He is on good terms with some "villains" who duplicate the gimmickry of Batman villains without committing any crimes, such as Jarvis Poker, the British Joker; the Knight and Squire have a longstanding enmity with agents of an alternate universe in which Britain is a fascist state. In #4, it is revea

Jacques-Henri Bernardin de Saint-Pierre

Jacques-Henri Bernardin de Saint-Pierre was a French writer and botanist. He is best known for his 1788 novel Paul et Virginie, now forgotten, but in the 19th century a popular children's book. At the age of twelve he had read Robinson Crusoe and went with his uncle, a skipper, to the West-Indies. After returning from this trip he was educated as an engineer at the École des Ponts, he joined the French Army and was involved in the Seven Years' War against Prussia and England. In 1768 he studied plants. In 1771 he became friendly with and a pupil of Jean-Jacques Rousseau. Together they studied the plants around Paris. In 1795 he was elected to the Institut de France, in 1797 manager of the Botanical Gardens and in 1803 member of the Académie française. Saint-Pierre was an avid advocate and practitioner of vegetarianism, although he was a devout Christian was heavily influenced by Enlightenment-era intellectuals like Voltaire and his mentor Rousseau. "Barye's predators devouring their living prey indulge the emotions in a Romantic way of course, but they embody a romantically moralizing point of view like those held by Bernardin de Saint-Pierre, Mme de Staël, Victor Hugo.

The Oeuvres complètes of Bernardin de Saint-Pierre appeared in Paris in 1834 and was known to Barye, for the author was the former director of the zoo in the Jardin des Plantes and one of the "masters of genuine poetry" for the archromantic Mme de Staël. Bernardin de Saint-Pierre maintained that a carnivorous animal in devouring its prey alive committed a sin against the laws of its own nature." Voyage à l’Île de France, à l’île Bourbon et au cap de Bonne-Espérance L’Arcadie Études de la nature Paul et Virginie La Chaumière indienne Le Café de Surate Les Vœux d’un solitaire De la nature de la morale Voyage en Silésie La Mort de Socrate Harmonies de la nature Society of the Friends of Truth Works by Jacques-Henri Bernardin de Saint-Pierre at Project Gutenberg Works by or about Jacques-Henri Bernardin de Saint-Pierre at Internet Archive Works by Jacques-Henri Bernardin de Saint-Pierre at LibriVox International Vegetarian Union,"The Ethics of Diet": Jacques-Henri Bernardin de Saint-Pierre