All articles starting with O
9,097 articles
Obrigheim Nuclear Power Plant
The Obrigheim Nuclear Power Plant (Kernkraftwerk Obrigheim, KWO) was a pressurized water reactor in Obrigheim, Germany, the country's first commercially used one, operating from 1968 to 2005.
Obruchev (lunar crater)
Obruchev is a 72.23-km-wide impact crater on the Moon's far side south of Mare Ingenii, Nectarian in age, named for Soviet geologist Vladimir Afanasievich Obruchev (1863-1956) and IAU-approved in 1970.
OBS Studio
OBS Studio, also known as Open Broadcaster Software, is a free, open-source program for recording and streaming video, developed by the nonprofit OBS Project since 2012 and used by tens of millions.
Obscene Extreme
Obscene Extreme is an annual extreme-music festival focused chiefly on grindcore, held at the Bojiště ground in Trutnov, Czech Republic, and first staged in 1999 by Miloslav "Čurby" Urbanec.
Obscene gesture
Obscene gesture: a hand or body movement whose conventional meaning in a culture is a sexual, scatological, or contemptuous insult. Covers the middle finger (digitus impudicus), fig sign, OK ring, and thumbs-up, whose meanings reverse across countries.
Obscenity
Obscenity: legally unprotected sexually explicit speech. Under the U.S. Miller test (1973) it must appeal to prurient interest, be patently offensive, and lack serious value; distinct from pornography and indecency.
Obscurantism
Obscurantism is the deliberate prevention of understanding, either by withholding knowledge or by writing in deliberately vague language, a pejorative term dating to 1801 and tied to Enlightenment attacks on opponents of inquiry.
Obscure gastrointestinal bleeding
Obscure gastrointestinal bleeding (OGIB) is bleeding from the digestive tract with no source found after negative endoscopy; it may be visible or hidden, such as iron-deficiency anemia.
Obscured by Clouds
Obscured by Clouds is Pink Floyd's seventh album (June 1972, Harvest), the soundtrack to Barbet Schroeder's film La Vallée, recorded in about a week at Château d'Hérouville and renamed after a dispute with the film company.
Observability
Observability is a property of dynamical systems, introduced by Rudolf Kalman in 1960, stating whether the full internal state can be inferred from measured outputs.
Observable
In quantum mechanics, an observable is a measurable physical quantity, such as position, momentum, energy, or spin, represented by a self-adjoint operator whose eigenvalues are the possible measurement results.
Observable universe
The observable universe, also called the visible universe, is the sphere of space about 46 billion light-years in radius from which light has reached Earth.
Observance of Christmas by country
Observance of Christmas by country covers where Christmas is a public holiday, at least 154 countries, the December 25 and January 7 calendar split, and national customs.
Observation
Observation, in science, is the gathering of empirical information about the world through sensing, often aided by instruments such as telescopes and microscopes, used as evidence in describing phenomena and testing theories.
Observation car
An observation car is a passenger railcar placed at the rear of a train so occupants can watch the track recede, first entering standard service in 1888.
Observation Commissioner (Guanchashi)
The Observation Commissioner (观察使) was a Tang dynasty office that in the late Tang served as one of two kinds of provincial governor, alongside the Military Commissioner.
Observational comedy
Observational comedy, also called observational humor, is a stand-up style built on everyday-life absurdities. Pioneered by David Brenner, popularized by Cosby, Carlin, and Jerry Seinfeld, and adapted to TV in Seinfeld.
Observational error
Observational error, also called measurement error, is the difference between a measured value of a quantity and its true value, divided into systematic and random components.
Observational learning
Observational learning, or modeling, is learning by watching others (models) and imitating them; central to Bandura's social learning theory, with four steps (attention, retention, reproduction, motivation), vicarious reinforcement, mirror-neuron and prefrontal mechanisms, and applications in education and motor skill learning.
Observational study
An observational study, as defined by William G. Cochran in 1965, investigates cause and effect without assigning exposures, making it possible where randomized trials would be unethical but leaving it vulnerable to bias.
Observations and explorations of Venus
Observations and explorations of Venus, also called the exploration of Venus, include over 40 spacecraft missions launched since 1961 that revealed a volcanic surface beneath permanent clouds.
ObservatoireEI study
ObservatoireEI (Observatoire EI, NCT03272724) is the French National Observatory on Infective Endocarditis, a prospective multicentre open cohort registry run from Nancy, enrolling adults with definite or possible IE since 2008.
Observe and Report
Observe and Report: 2009 American black comedy written and directed by Jody Hill, starring Seth Rogen as delusional mall security head Ronnie Barnhardt chasing a flasher; Warner Bros. release, $27 million worldwide gross, 51% on Rotten Tomatoes.
Observe.Ai
Observe.AI is a contact-center AI company founded in 2017 and headquartered in San Francisco, whose platform transcribes and evaluates customer service calls to coach agents.
Observer (video game)
Observer (>observer) is a 2017 first-person psychological horror game by Bloober Team, set in 2084 Krakow, where detective Daniel Lazarski, voiced by Rutger Hauer, hacks minds with the Dream Eater; System Redux remaster followed in 2020.
Observer design
Observer design is the construction of a state observer, a dynamical system that estimates a plant's internal states from measured inputs and outputs, introduced by David G. Luenberger in 1964.
Observer effect (physics)
The observer effect in physics is the disturbance of a measured system by measurement itself; in quantum mechanics even an ideal measurement changes the state.
Observer pattern
The observer pattern is a software design pattern in which a subject maintains a list of observers and notifies them automatically when its state changes.
Observer-expectancy effect
The observer-expectancy effect, also called experimenter bias or the Clever Hans effect, is a research bias in which researchers' expectations unintentionally shape results, without conscious fraud, by cueing subjects.
Obsess (2026 film)
Obsess (2026) is a Hindi-language Indian psychological thriller directed by Peter Wilson, written by Sam Bariah, starring Eisha Singh and Peter Wilson, produced by Jagraj Motion Pictures, released 29 May 2026; distinct from Curry Barker's Hollywood horror Obsession.