An observer is one who engages in observation or in watching an experiment. Observer may also refer to:

Computer science and information theory

* In

information theory Information theory is the scientific study of the quantification (science), quantification, computer data storage, storage, and telecommunication, communication of information. The field was originally established by the works of Harry Nyquist a ...

, any system which receives information from an object *

State observer In control theory, a state observer or state estimator is a system that provides an estimate of the internal state of a given real system, from measurements of the input and output of the real system. It is typically computer-implemented, and pr ...

in control theory, a system that models a real system in order to provide an estimate of its internal state * Observer pattern, a design pattern used in computer programming

Fiction

* ''Observer'' (video game), a cyberpunk horror video game * Observer (''Mystery Science Theater 3000''), a fictional television character * Observers, beings in the television show ''Fringe''

Military

* Air observer, an aircrew member *

Artillery observer An artillery observer, artillery spotter or forward observer (FO) is responsible for directing artillery and mortar fire onto a target. It may be a ''forward air controller'' (FAC) for close air support (CAS) and spotter for naval gunfire su ...

, a front line personnel who directs fire discipline for artillery strikes * Royal Observer Corps, a civil defence organisation, originally tasked with reporting enemy aircraft * Observer, a non-participating officer, or

umpire An umpire is an official in a variety of sports and competition, responsible for enforcing the rules of the sport, including sportsmanship decisions such as ejection. The term derives from the Old French nonper, ''non'', "not" and ''per'', ...

, tasked with observing the actions of soldiers during a field training or military exercise

Music

* "Observer", a song by Gary Numan on his album '' The Pleasure Principle'' * "The Observer", a track from The Flaming Lips' 1999 album ''

The Soft Bulletin ''The Soft Bulletin'' is the ninth studio album by American rock band the Flaming Lips, released by Warner Bros. Records on May 17, 1999, in the United Kingdom, and on June 22, 1999, in the United States. The album was released to widespread accla ...

'' * The Observers, an alternative name for reggae session band

Soul Syndicate Soul Syndicate, originally called the Rhythm Raiders, were one of the top reggae session bands in Jamaica from the early 1970s to the mid-1980s. History In the first half of the 1970s the band from the Greenwich Farm area of Kingston recorded ...

* Niney the Observer (born 1951), Jamaican record producer and singer

Publications

Observer.com ''The New York Observer'' was a weekly newspaper printed from 1987 to 2016, when it ceased print publication and became the online-only newspaper ''Observer''. The media site focuses on culture, real estate, media, politics and the entertainmen ...

, an online-only version of the weekly newspaper ''The New York Observer'' * ''Sunday Observer'' (Sri Lanka), a weekly newspaper * ''Observer'' (APS), a member magazine of Association for Psychological Science * ''The Observer'' (disambiguation), any of various periodicals

Science

* Observer (general relativity) *

Observer (meteorological) A meteorological observer, or weather observer, is a person authorized by a weather authority to make or record meteorological observations. They are technicians who are responsible for the accurate observation, rapid measurement, timely collectio ...

* Observer (physics) *

Observer (quantum physics) Some interpretations of quantum mechanics posit a central role for an observer of a quantum phenomenon. The quantum mechanical observer is tied to the issue of observer effect, where a measurement necessarily requires interacting with the physical o ...

* Observer (special relativity) *

Observational astronomy Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical m ...

Other uses

* Observer status, granted by an organization to allow a non-member limited participation * An election observer, one who assists in election monitoring * A game official sometimes used in the sport

Ultimate Ultimate or Ultimates may refer to: Arts, entertainment, and media Music Albums * ''Ultimate'' (Jolin Tsai album) * ''Ultimate'' (Pet Shop Boys album) *''Ultimate!'', an album by The Yardbirds *''The Ultimate (Bryan Adams Album)'', a compilatio ...

* The Observer type in the Enneagram of Personality model *

Donald Alaster Macdonald Donald Alaster Macdonald (6 June 1859 – 23 November 1932) was an Australian journalist and nature writer, writing under the pen names including 'Observer' and 'Gnuyang' (gossip).Hugh Anderson,Macdonald, Donald Alaster (1859–1932), ''Austral ...

(1859–1932), Australian journalist who wrote under the pseudonym 'Observer'