cluster

In music, the effect of playing simultaneously and without emphasis all the notes within a chosen interval. It was introduced by the US composer Henry Cowell in the piano piece The Banshee (1925), for which using a ruler on the keys is recommended. Its use in film and radio incidental music symbolizes a hallucinatory or dreaming state, presumably because it resembles an internalized disturbance of normal hearing.

The cluster effect is also heard in Ecuatorial (1933-34) by Edgard Varèse, Karlheinz Stockhausen's Piano Piece X (1961), and György Ligeti's Volumina (1962) for organ, using the player's forearms. Cluster writing for strings features in Krzysztof Penderecki's Threnody for the Victims of Hiroshima (1960), and for voices in Ligeti's Lux Aeterna.

Cluster

European Space Agency two-year project to study the interaction of the solar wind, a stream of atomic particles from the Sun's corona, with the Earth's magnetosphere, from an array of four identical Earth-orbiting satellites that can provide a three-dimensional view. The first pair of the Cluster II space weather satellites was launched in July 2000, and the second pair the following month.

The Ariane 5 rocket carrying the first Cluster probes exploded due to a software fault 37 seconds after lift-off on 4 June 1996. New probes had to be built for launch in 2000 by the Russian Soyuz-Fregat craft. The probes function in a tetrahedral formation, separated by several thousand kilometres.

Cluster works in conjunction with the Solar and Heliospheric Observatory and the two Chinese Double Star satellites.

cluster

In business, a collection of businesses operating in the same industry gathered in a single geographical location. For example, Internet clusters include Silicon Valley, California, in the USA, and Silicon Fen around Cambridge in England.