CZ:Featured article/Current: Difference between revisions

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{{Image|Apollo 11 image 2.jpg|right|200px|The first manned landing on the moon was successfully accomplished by the Apollo 11 mission on July 20, 1969. Astronaut Neil Armstrong took this photograph of fellow astronaut Edwin ("Buzz") Aldrin walking on the Moon's surface during lunar landing.}}
[[Image:Roger_Federer.jpg|thumb|left|{{#ifexist:Template:Roger Federer.jpg/credit|{{Roger Federer.jpg/credit}}<br/>|}}Roger Federer, a professional tennis player, hitting a forehand against James Blake in the quarterfinals of the 2006 U.S. Open.]]


The '''[[Apollo program]]''' was a series of human spaceflight missions undertaken by the United States, during the years 1961–1974, using the Apollo spacecraft and Saturn space launch vehicle. It was conducted by the National Aeronautics and Space Administration (NASA) and was devoted to the goal, expressed in a 1961 address to the U.S. Congress by U.S. President John F. Kennedy, of "... landing a man on the Moon and returning him safely to the Earth ..." within the decade of the 1960s. That goal was successfully achieved by the Apollo 11 mission in July 1969.
'''Tennis''' is a sport played between either two players ("singles") or two teams of two players ("doubles"). Players use a stringed racquet to strike a hollow rubber ball covered with felt over a net into the opponent's court. In some places tennis is still called '''lawn tennis''' to distinguish it from ''real tennis'' (also known as ''royal tennis'' or ''court tennis''), an older form of the game that originated in France in the Middle Ages and is played indoors on a very different court. Originating in England in the late nineteenth century, lawn tennis first spread throughout the English-speaking world, particularly among the upper classes. Today tennis is an Olympic sport that is played at all levels of society, by all ages, and in many countries around the world. Except for the adoption of the tie-breaker in the 1970s, its rules have remained remarkably unchanged since the 1890s. Millions of people also follow tennis as a spectator sport, especially the four Grand Slam tournaments.  


The program continued until 1975 with five subsequent Apollo missions which also landed astronauts on the Moon, the last in December 1972. In the six successful Apollo spaceflights, twelve men walked on the Moon. As of 2011, these are the only times that humans have landed on another celestial body.  
==Manner of play==
===The court===
Tennis is played on a rectangular, flat surface that can be composed of various materials.  The court is 78 feet (23.77 meters) long and its width is 27 feet (8.23 m) for singles matches and 36 feet (10.97 m) for doubles matches. Additional clear space around the court is required in order for players to reach balls. A net is stretched across the full width of the court, parallel with the baselines, dividing it into two equal areas. The net is 3 feet 6 inches (1.07 m) high at the posts and 3 feet (914 mm) high in the center.  


Equipment that was originally produced for the Apollo program was used for the later Skylab program during 1973–1974 and the joint U.S.−Soviet mission (Apollo−Soyuz Test Project) in 1975. Therefore, those subsequent programs are thus often considered to be part of the Apollo program.
====''The lines''====
 
The two lines that delineate the width of the court are called the baseline. The short mark in the center of each baseline is referred to as either the hash mark or the center mark. The outermost lines that make up the length are both called the doubles sideline. These are the boundaries used when doubles is being played. The area between the doubles sideline and the lines next to them is called the doubles alley, which is considered to be "out" in singles play. These lines next to the doubles sideline are the singles sidelines, and are used as boundaries in singles play. The line that runs across the center of a player's side of the court is called the service line; despite its name this is not where a player legally stands when making a serve. The line dividing the service line in two is called the center line or center service line.  The boxes that this center line creates are called the service boxes; depending on a player's position, they will have to hit the ball into one of these when serving.
Despite the many successes, there were two major failures, the first of which resulted in the deaths of three astronauts, Virgil "Gus" Grissom, Ed White and Roger Chaffee, in the Apollo 1 launchpad fire. The second was an explosion on Apollo 13, in whose aftermath the deaths of three more astronauts were averted by the efforts of flight controllers, project engineers, and backup crew members.
 
The Apollo program was named after the Greek god of the Sun.
 
==Background==
 
The Apollo program was originally conceived early in 1960, during the administration of U.S. President Eisenhower, as a follow-up to America's Mercury program. While the Mercury capsule could only support one astronaut on a limited Earth orbital mission, the Apollo spacecraft was intended to be able to carry three astronauts on a circumlunar flight and perhaps even on a lunar landing. The program was named after the Greek god of the Sun by NASA manager Abe Silverstein, who later said that "I was naming the spacecraft like I'd name my baby." While NASA went ahead with planning for Apollo, funding for the program was far from certain, particularly given Eisenhower's equivocal attitude to manned spaceflight.
 
[[Apollo program|...]]

Revision as of 14:41, 2 July 2011

(CC) Photo: John Togasaki
Roger Federer, a professional tennis player, hitting a forehand against James Blake in the quarterfinals of the 2006 U.S. Open.

Tennis is a sport played between either two players ("singles") or two teams of two players ("doubles"). Players use a stringed racquet to strike a hollow rubber ball covered with felt over a net into the opponent's court. In some places tennis is still called lawn tennis to distinguish it from real tennis (also known as royal tennis or court tennis), an older form of the game that originated in France in the Middle Ages and is played indoors on a very different court. Originating in England in the late nineteenth century, lawn tennis first spread throughout the English-speaking world, particularly among the upper classes. Today tennis is an Olympic sport that is played at all levels of society, by all ages, and in many countries around the world. Except for the adoption of the tie-breaker in the 1970s, its rules have remained remarkably unchanged since the 1890s. Millions of people also follow tennis as a spectator sport, especially the four Grand Slam tournaments.

Manner of play

The court

Tennis is played on a rectangular, flat surface that can be composed of various materials. The court is 78 feet (23.77 meters) long and its width is 27 feet (8.23 m) for singles matches and 36 feet (10.97 m) for doubles matches. Additional clear space around the court is required in order for players to reach balls. A net is stretched across the full width of the court, parallel with the baselines, dividing it into two equal areas. The net is 3 feet 6 inches (1.07 m) high at the posts and 3 feet (914 mm) high in the center.

The lines

The two lines that delineate the width of the court are called the baseline. The short mark in the center of each baseline is referred to as either the hash mark or the center mark. The outermost lines that make up the length are both called the doubles sideline. These are the boundaries used when doubles is being played. The area between the doubles sideline and the lines next to them is called the doubles alley, which is considered to be "out" in singles play. These lines next to the doubles sideline are the singles sidelines, and are used as boundaries in singles play. The line that runs across the center of a player's side of the court is called the service line; despite its name this is not where a player legally stands when making a serve. The line dividing the service line in two is called the center line or center service line. The boxes that this center line creates are called the service boxes; depending on a player's position, they will have to hit the ball into one of these when serving.

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