Four-velocity

In physics, in particular in special relativity and general relativity, a four-velocity is a four-vector in four-dimensional spacetime that represents the relativistic counterpart of velocity, which is a three-dimensional vector in space.

Physical events correspond to mathematical points in time and space, the set of all of them together forming a mathematical model of physical four-dimensional spacetime. The history of an object traces a curve in spacetime, called its world line. If the object is massive, so that its speed is less than the speed of light, the world line may be parametrized by the proper time of the object. The four-velocity is the rate of change of four-position with respect to the proper time along the curve. The velocity, in contrast, is the rate of change of the position in (three-dimensional) space of the object, as seen by an observer, with respect to the observer's time.

The value of the magnitude of an object's four-velocity, i. e. the quantity obtained by applying the metric tensor g to the four-velocity u, that is ||u||² = u ⋅ u = g_μνu^νu^μ, is always equal to ±c², where c is the speed of light. Whether the plus or minus sign applies depends on the choice of metric signature. For an object at rest its four-velocity is parallel to the direction of the time coordinate with u⁰ = c. A four-velocity is thus the normalized future-directed timelike tangent vector to a world line, and is a contravariant vector. Though it is a vector, addition of two four-velocities does not yield a four-velocity: The space of four-velocities is not itself a vector space.

10 Speed (album)

10 Speed is the second studio album by the Canadian rock band Mystery Machine. It was released in Jan 23, 1996 on the Nettwerk America label. 10 Speed was a notable album for being one of the first forays into mixing media and music in compact discs.

Track listing

External links

10 Speed

Speed 2: Cruise Control

Speed 2: Cruise Control is a 1997 American disaster thriller film, and a sequel to the enormously popular Speed (1994). The film was produced and directed by Jan de Bont, and written by Randall McCormick and Jeff Nathanson, based on a story by de Bont and McCormick. Sandra Bullock stars in the film, reprising her role from Speed, while Jason Patric and Willem Dafoe co-star. The film was released by 20th Century Fox on June 13, 1997.

The plot involves couple Annie and Alex taking a vacation in the Caribbean aboard a luxury cruise ship, which is hijacked by a villain named Geiger who hacked into the ship's computer system. As they are trapped aboard the ship, Annie and Alex work with the ship's first officer to try to stop the ship, which they discover is programmed to crash into an oil tanker.

De Bont came up with the idea for the film after he had a recurring nightmare about a cruise ship crashing into an island. Speed star Keanu Reeves was initially supposed to reprise his role as Jack Traven for the sequel, but decided not to commit and was replaced by Patric prior to filming. Production took place aboard Seabourn Legend, the ship on which the film is set. The film's final scene, where the ship crashes into the island of Saint Martin, cost almost a quarter of the film's budget, and set records as the largest and most expensive stunt ever filmed. Many interior scenes aboard the ship were shot on soundstages in the Greater Los Angeles Area. The film's soundtrack featured mostly reggae music. Mark Mancina returned to compose the film score, which was released as an album 13 years after the film's release.

White

White is an achromatic color, literally a "color without hue", that is a mixture of the frequencies of all the colors of the visible spectrum. It is one of the most common colors in nature, the color of sunlight, snow, milk, chalk, limestone and other common minerals. In many cultures white represents or signifies purity, innocence, and light, and is the symbolic opposite of black, or darkness. According to surveys in Europe and the United States, white is the color most often associated with perfection, the good, honesty, cleanliness, the beginning, the new, neutrality, and exactitude.

In ancient Egypt and ancient Rome, priestesses wore white as a symbol of purity, and Romans wore a white toga as a symbol of citizenship. In the Middle Ages and Renaissance a white unicorn symbolized chastity, and a white lamb sacrifice and purity; the widows of kings dressed in white rather than black as the color of mourning. It sometimes symbolizes royalty; it was the color of the French kings (black being the color of the queens) and of the monarchist movement after the French Revolution as well as of the movement called the White Russians (not to be confounded with Belarus, literally "White Russia") who fought the Bolsheviks during the Russian Civil War (1917-1922). Greek and Roman temples were faced with white marble, and beginning in the 18th century, with the advent of neoclassical architecture, white became the most common color of new churches, capitols and other government buildings, especially in the United States of America. It was also widely used in 20th century modern architecture as a symbol of modernity, simplicity and strength.

White and Black in chess

In chess, the player who moves first is referred to as "White" and the player who moves second is referred to as "Black". Similarly, the pieces that each conducts are called, respectively, "the white pieces" and "the black pieces". The pieces are often not literally white and black, but some other colors (usually a light color and a dark color, respectively). The 64 squares of the chessboard, which is colored in a checkered pattern, are likewise referred to as "white squares" or "light squares" on the one hand, and "black squares" or "dark squares" on the other. In most cases, the squares are not actually white and black, but a light color and a contrasting dark color. For example, the squares on plastic boards are often off-white ("buff") and green, while those on wood boards are often light brown and dark brown.

In old chess writings, the sides are often called Red and Black, because those were the two colors of ink then commonly available when hand-drawing or printing chess position diagrams.

White (surname)

White is a surname either of English or of Scottish and Irish origin, the latter being an anglicisation of the Scottish Gaelic MacGillebhàin, "Son of the fair gillie" and the Irish "Mac Faoitigh" or "de Faoite". It is the seventeenth most common surname in England. In the 1990 United States Census, "White" ranked fourteenth among all reported surnames in frequency, accounting for 0.28% of the population. By 2000, White had fallen to position 20 in the United States and 22nd position by 2014

Notable people with the surname include:

A–B

Love (given name)

Love, or more uncommon Lowe, is a Swedish version of the French name Louis. It can also be a version of Lovisa, and can thus be used both for men and women, although it is more common with men.

The name is uncommon amongst adults; there are less than 200 men older than 30 in Sweden with the name, but several hundreds from every cohort born in the 1990s. 31 December 2009, there was in total 6,058 men in Sweden with the name Love/Lowe, of which 2,953 had it as first nnameame, the rest as middle name. There were also 531 women with the name, of which 128 had it as given name.

In 2003, 344 boys got the name, and of those, 182 got it as given name. The same year, 24 girls got the name, of which 6 got it as given name.

The name day in Sweden is 2 October (1986-1992: 3 December; 1993-2000: 26 November).

Persons with the name Love or Lowe

References

SCB