Photometry, from Greek photo- ("light") and -metry ("measure"), is a technique used in astronomy that is concerned with measuring the flux or intensity of light radiated by astronomical objects. This light is measured through a telescope using a photometer, often made using electronic devices such as a CCD photometer or a photoelectric photometer that converts light into an electric current by the photoelectric effect. When calibrated against standard stars (or other light sources) of known intensity and colour, photometers can measure the brightness or apparent magnitude of celestial objects. The methods used to perform photometry depend on the wavelength region under study. At its most basic, photometry is conducted by gathering light and passing it through specialized photometric optical bandpass filters, and then capturing and recording the light energy with a photosensitive instrument. Standard sets of passbands (called a photometric system) are defined to allow accurate comparison of observations. A more advanced technique is spectrophotometry that is measured with a spectrophotometer and observes both the amount of radiation and its detailed spectral...

Canoe slalom (previously known as whitewater slalom) is a competitive sport with the aim to navigate a decked canoe or kayak through a course of hanging downstream or upstream gates on river rapids in the fastest time possible. It is one of the two kayak and canoeing disciplines at the Summer Olympics, and is referred to by the International Olympic Committee (IOC) as Canoe/Kayak Slalom. The other Olympic canoeing discipline is canoe sprint. Wildwater canoeing is a non-Olympic paddlesport. History Canoe slalom racing started in Switzerland in 1933, initially on a flatwater course. In 1946, the International Canoe Federation (ICF), which governs the sport, was formed. The first World Championships were held in 1949 in Switzerland. From 1949 to 1999, the championships were held every odd-numbered year and have been held annually in non-Summer Olympic years since 2002. Folding kayaks were used from 1949 to 1963; and in the early 1960s, boats were made of fiberglass and nylon. Boats were heavy, usually over 30 kilos (65 pounds). With the advent of kevlar and carbon fiber being used in the 1970s, the widths of the boats were reduced...

The Dark Knight is a 2008 superhero film directed by Christopher Nolan from a screenplay co-written with his brother Jonathan. Based on the DC Comics superhero, Batman, it is the sequel to Batman Begins (2005) and the second installment in The Dark Knight Trilogy. The plot follows the vigilante Batman, police lieutenant James Gordon, and district attorney Harvey Dent, who form an alliance to dismantle organized crime in Gotham City. Their efforts are derailed by the Joker, an anarchistic mastermind who seeks to test how far Batman will go to save the city from chaos. The ensemble cast includes Christian Bale, Michael Caine, Heath Ledger, Gary Oldman, Aaron Eckhart, Maggie Gyllenhaal, and Morgan Freeman. Warner Bros. Pictures prioritized a sequel following the successful reinvention of the Batman film series with Batman Begins. Christopher and Batman Begins co-writer David S. Goyer developed the story elements, making Dent the central protagonist caught up in the battle between Batman and the Joker. In writing the screenplay, the Nolans were influenced by 1980s Batman comics and crime...