Often called “chess on ice,” the 500-year-old ice sport of curling is relatively unknown in the United States. Curling, first named an Olympic sport in 1998, consists of two teams throwing stones down a sheet of ice with the goal of placing the player’s team’s stones closest to the center of a ring of circles at the end of the sheet of ice.

Curling is a game much more of strategy than athletic ability. Teams consist of four members each: a lead, second, vice skip and skip. The skip is the captain of the team who calls the shots at the opposite end of the 126-foot long sheet of ice from where one of the curlers is throwing the 42-pound granite stone. The other two members, who are not throwing, are sweepers.

The brooms used by the sweepers serve two purposes. First, sweeping melts the ice and makes the stone travel further. Secondly, sweeping helps stop the stone from curling from one side to the other. Depending how the thrower lets go of the stone — turning it clockwise or counter clockwise — the stone will move in the direction of the turn.

Sweeping keeps the stone from moving too far to one side or the other, depending upon the shot the skip wants the thrower to make. If the skip wants the curler to hit the other team’s stone out of the circle, the skip will have the curler aim close to the stone and throw it fast. The sweepers will then sweep in front of the stone to keep it on target. The slower a stone is thrown, the more it will curl.

The game progresses as each person throws two stones each, alternating with the other team, towards a circle of concentric rings at the other end of the ice. The goal — to get your team’s stone closest to the button, or center. Each round of play is called an end, and the team whose stone is closest to the center after all the stones have been thrown gets points.

The number of points awarded depends upon how many of the winning team’s stones are closest to the center before one of the other team’s stones outranks them. Ten ends are played in each game. and the team with the most points at the end wins. The number of points a team scores is usually one to three, and an eight-point end (all of one team’s stones in scoring position) is extremely rare.

Strategy in the sport involves placing the stones throughout the circle so the other team cannot knock all of the opponent’s stones out. For instance, guard stones will be placed in front of the circle to protect the other team from hitting out any stones close to the center.

Other options a curler could throw would be a draw, which means having the curler throw the stone at normal weight, or speed, so it ended up in the middle of the circles. To knock another team’s stone out, the curler would throw the stone at top speed and aim close to the stone, since it will not curl as much when it moves that fast.

Curling was started in Scotland in the 16th century. Originally played on marshes and lagoons, it eventually evolved into the game it is today. Curling came to North America with the British troops in the 18th century and is much more popular in Canada (the country has 1.2 million curlers) than in the United States (with 15,000 curlers).

In the 2002 Salt Lake City Games, the United States is represented by team Somerville on the men’s side and team Erickson on the women’s. Play started Feb. 11 and will end with the women’s gold medal game Feb. 21 and the men’s gold medal game Feb. 22.