Quincunx facts for kids
A quincunx // is a geometric pattern consisting of five points arranged in a cross, with four of them forming a square or rectangle and a fifth at its center. It forms the arrangement of five units in the pattern corresponding to the five-spot on six-sided dice, playing cards, and dominoes.
Historical origins of the name
The quincunx was originally a coin issued by the Roman Republic c. 211–200 BC, whose value was five twelfths (quinque and uncia) of an as, the Roman standard bronze coin. On the Roman quincunx coins, the value was sometimes indicated by a pattern of five dots or pellets. However, these dots were not always arranged in a quincunx pattern.
The Oxford English Dictionary (OED) dates the first appearances of the Latin word in English as 1545 and 1574 ("in the sense 'five-twelfths of a pound"). The first citation for "A pattern used for planting trees" dates from 1606. The OED also cites a 1647 reference to the German astronomer Kepler to the astronomical/astrological meaning. Jackson (1821) states that the word refers to the pattern of trees in an orchard, but then uses it more abstractly for a version of the orchard-planting problem involving patterns of points and lines in the plane (for which the quincunx pattern provides the optimal solution for five points).
Quincunx patterns occur in many contexts:
- In heraldry, groups of five elements (charges) are often arranged in a quincunx pattern, called in saltire in heraldic terminology. The flag of the Solomon Islands features this pattern, with its five stars representing the five main island groups in the Solomon Islands. Another instance of this pattern occurred in the flag of the 19th-century Republic of Yucatán, where it signified the five departments into which the republic was divided.
- A quincunx is a standard pattern for planting an orchard.
- Francis Galton's "quincunx" (referred to later as a "bean machine") is a physical demonstration of how the central limit theorem leads to a normal distribution; its pins are laid out in a quincunx pattern.
- Quincunxes are used in modern computer graphics as a pattern for multisample anti-aliasing. Quincunx antialiasing samples scenes at the corners and centers of each pixel. These five sample points, in the shape of a quincunx, are combined to produce each displayed pixel. However, samples at the corner points are shared with adjacent pixels, so the number of samples needed is only twice the number of displayed pixels.
- In numerical analysis, the quincunx pattern describes the two-dimensional five-point stencil, a sampling pattern used to derive finite difference approximations to derivatives.
- In architecture, a quincuncial plan, also defined as a "cross-in-square", is the plan of an edifice composed of nine bays. The central and the four angular ones are covered with domes or groin vaults so that the pattern of these domes forms a quincunx; the other four bays are surmounted by barrel vaults. In Khmer architecture, the towers of a temple, such as Angkor Wat, are sometimes arranged in a quincunx to represent the five peaks of Mount Meru.
- A quincunx is one of the quintessential designs of Cosmatesque inlay stonework.
- A quincuncial map is a conformal map projection that maps the poles of the sphere to the centre and four corners of a square, thus forming a quincunx.
- The points on each face of a unit cell of a face-centred cubic lattice form a quincunx.
- The quincunx as a tattoo is known as the five dots tattoo. It has been variously interpreted as a fertility symbol, a reminder of sayings on how to treat women or police, a recognition symbol among the Romani people, a group of close friends, standing alone in the world, or time spent in prison (with the outer four dots representing the prison walls and the inner dot representing the prisoner). Thomas Edison, whose many inventions included an electric pen which later became the basis of a tattooing machine created by Samuel O'Reilly, had this pattern tattooed on his forearm.
- The first two stages of the Saturn V super heavy-lift rocket had engines in a quincunx arrangement.
- A baseball diamond forms a quincunx with the four bases and the pitcher's mound.
Quincunx Facts for Kids. Kiddle Encyclopedia.