Sky

The sky (or celestial dome) is everything that lies above the surface of the Earth, including the atmosphere and outer space.

In the field of astronomy, the sky is also called the celestial sphere. This is viewed from Earth's surface as an imaginary dome where the sun, stars, planets, and the moon are seen to be traveling. The celestial sphere is conventionally divided into regions called constellations. Usually, the term sky is used informally as the point of view from the Earth's surface; however, the meaning and usage can vary. In some cases, such as in discussing the weather, the sky refers to only the lower, more dense portions of the atmosphere.

During daylight, the sky appears to be blue because air scatters blue sunlight more than it scatters red. At night, the sky appears to be a mostly dark surface or region scattered with stars. During the day, the Sun can be seen in the sky unless obscured by clouds. In the night sky (and to some extent during the day) the moon, planets and stars are visible in the sky. Some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation can also be seen in the sky during storms. Birds, insects, aircraft, and kites are often considered to fly in the sky. Due to human activities, smog during the day and light pollution during the night are often seen above large cities.

TheSky (astronomy software)

TheSky is an astronomy application designed to be used for educational, observational purposes. TheSky provides an extensive feature set including the following:

The Sky (album)

The Sky is the third in a trilogy of albums with music by Anita Kerr, words by Rod McKuen, and featuring the San Sebastian Strings. The first two albums in the trilogy were titled The Sea and The Earth.

Track listing

Side one

Side two

External links

Graph (discrete mathematics)

In mathematics, and more specifically in graph theory, a graph is a representation of a set of objects where some pairs of objects are connected by links. The interconnected objects are represented by mathematical abstractions called vertices (also called nodes or points), and the links that connect some pairs of vertices are called edges (also called arcs or lines). Typically, a graph is depicted in diagrammatic form as a set of dots for the vertices, joined by lines or curves for the edges. Graphs are one of the objects of study in discrete mathematics.

The edges may be directed or undirected. For example, if the vertices represent people at a party, and there is an edge between two people if they shake hands, then this is an undirected graph, because if person A shook hands with person B, then person B also shook hands with person A. In contrast, if there is an edge from person A to person B when person A knows of person B, then this graph is directed, because knowledge of someone is not necessarily a symmetric relation (that is, one person knowing another person does not necessarily imply the reverse; for example, many fans may know of a celebrity, but the celebrity is unlikely to know of all their fans). The former type of graph is called an undirected graph and the edges are called undirected edges while the latter type of graph is called a directed graph and the edges are called directed edges.

Edge (surname)

Edge is a surname. Notable people with the surname include:

Edge (geometry)

In geometry, an edge is a particular type of line segment joining two vertices in a polygon, polyhedron, or higher-dimensional polytope. In a polygon, an edge is a line segment on the boundary, and is often called a side. (Thus a segment joining two vertices while passing through the interior or exterior is not an edge but instead is called a diagonal.) In a polyhedron or more generally a polytope, an edge is a line segment where two two-dimensional faces meet.

Relation to edges in graphs

In graph theory, an edge is an abstract object connecting two graph vertices, unlike polygon and polyhedron edges which have a concrete geometric representation as a line segment. However, any polyhedron can be represented by its skeleton or edge-skeleton, a graph whose vertices are the geometric vertices of the polyhedron and whose edges correspond to the geometric edges. Conversely, the graphs that are skeletons of three-dimensional polyhedra can be characterized by Steinitz's theorem as being exactly the 3-vertex-connected planar graphs.

Sky blue

Sky blue is the name of a color that resembles the color of the sky at noon. The entry for "sky-blue" in Murray's New English Dictionary (1919) reports a first sighting of the term in the article on "silver" in Ephraim Chambers's Cyclopaedia of 1728. However, many writers had used the term "sky blue" to name a color before Chambers. For example, we find "sky blue" in A Collection of Voyages and Travels (London: Awnsham and John Churchill, 1704), vol. 2, p. 322, where John Nieuhoff describes certain flowers: "they are of a lovely sky blue colour, and yellow in the middle". The sense of this color may have been first used in 1585 in a book by Nicolas De Nicolay where he stated "the tulbant of the merchant must be skie coloured".

Displayed at right is the web colour sky blue.

Variations of sky blue

Celeste

Celeste (pronounced che-les-te in Italian se-lest in English) is the colloquial name for the pale turquoise blue colour associated with Italian bicycle manufacturer Bianchi S.p.A and sometimes known as Bianchi Green. In Italian, as the name indicates (Celestial), it is an attempt to reproduce the colour of clear skies. In English, this colour may also be referred to as Italian sky blue.