Ragtime, also spelled rag-time or rag time, is a musical style that had its peak from the 1890s to 1910s. Its cardinal trait is its syncopated or "ragged" rhythm. Ragtime was popularized during the early 20th century by composers such as Scott Joplin, James Scott and Joseph Lamb. Ragtime pieces (often called "rags") are typically composed for and performed on piano, though the genre has been adapted for a variety of instruments and styles. Ragtime music originated within African-American communities in the late 19th century and became a distinctly American form of popular music. It is closely related to marches, with additional polyrhythms from African music. Ragtime pieces usually contain several distinct themes, often arranged in patterns of repeats and reprises. Scott Joplin, known as the "King of Ragtime," gained fame through compositions like "Maple Leaf Rag" and "The Entertainer". Ragtime influenced early jazz, Harlem stride piano, Piedmont blues, and European classical composers such as Erik Satie, Claude Debussy, and Igor Stravinsky. Despite being overshadowed by jazz in the 1920s, ragtime has experienced several revivals...

Dowsing is a type of divination employed in attempts to locate ground water, buried metals or ores, gemstones, oil, claimed radiations (radiesthesia), gravesites, malign "earth vibrations" and many other objects and materials without the use of a scientific apparatus. It is also known as divining (especially in water divining), doodlebugging (particularly in the United States, in searching for petroleum or treasure) or (when searching for water) water finding, or water witching (in the United States). A Y-shaped twig or rod, or two L-shaped ones—individually called a dowsing rod, divining rod (Latin: virgula divina or baculus divinatorius), vining rod, or witching rod—are sometimes used during dowsing, although some dowsers use other equipment or no equipment at all. The motion of such dowsing devices is generally attributed to the ideomotor phenomenon, a psychological response where a subject makes motions unconsciously. Put simply, dowsing rods respond to the user's accidental or involuntary...

In 2-dimensional geometry, a glide reflection (or transflection) is a symmetry operation that consists of a reflection over a line and then translation along that line, combined into a single operation. The intermediate step between reflection and translation can look different from the starting configuration, so objects with glide symmetry are in general, not symmetrical under reflection alone. In group theory, the glide plane is classified as a type of opposite isometry of the Euclidean plane. A single glide is represented as frieze group p11g. A glide reflection can be seen as a limiting rotoreflection, where the rotation becomes a translation. It can also be given a Schoenflies notation as S2∞, Coxeter notation as [∞+,2+], and orbifold notation as ∞×. Description The combination of a reflection in a line and a translation in a perpendicular direction is a reflection in a parallel line. However, a glide reflection cannot be reduced like that. Thus the effect of a reflection combined with any translation is a glide reflection, with as special case just a reflection...

Counter-battery fire (sometimes called counter-fire) is a battlefield tactic employed to defeat the enemy's indirect fire elements (multiple rocket launchers, artillery and mortars), including their target acquisition, as well as their command and control components. Counter-battery arrangements and responsibilities vary between nations but involve target acquisition, planning and control, and counter-fire. Counter-battery fire rose to prominence in World War I. Counter-battery radar detects incoming indirect fire and calculates its point of origin. That location data can be sent by a communications link to friendly forces, who can then fire on the enemy positions, hopefully before they can reposition (the "scoot" part of shoot-and-scoot tactics). Counter-RAM systems track incoming rocket, artillery, and mortar fire and attempt to intercept and destroy the projectiles or provide early warning to the target area. Background Indirect fire was introduced so that artillery could fire from behind cover to reduce its exposure to enemy artillery by making itself more difficult to find. While armies were doing this, little...