Curling is a sport in which players slide large, heavy stones across the ice to reach a target. It began in Scotland in the 1500s and spread to other parts of Europe and North America in the 1800s. Since then, it has come to be popular throughout the world because of the strategy and skill it requires. Players must not only possess the physical strength to slide the stones across the ice, but also develop the mental skills for planning their moves to defeat their opponents. These qualities have earned the sport the name “chess on ice.” Since 1998 it has been an official sport in the Winter Olympics.

Curling matches are played on a sheet of ice that measures around 45 meters in length and 5 meters in width. At each end of the sheet is the target, or “house,” which comprises three concentric rings. The largest one measures 3.66 meters in diameter. The main equipment used in curling is the stone, which weighs between 17 and 20 kilograms, and the broom, or brush, which has a long handle and is used to sweep the ice in front of the stone.

To play the game, two teams of four players each slide stones over the ice. Each player on each team slides two stones each, for a total of 16 stones; this is called an end. One game in curling consists of either eight or ten ends; there are ten ends in Olympic curling. One player releases the stone upon the instructions of another player, the “skip,” while the other two players sweep the ice in front of the stone. The objective for each team is to score the most points. To score points, players try to place their stones as close as possible to the center of the house. When each end is finished, only the team with the stone closest to the center earns points for each of its stones in the house that is closer than the opponent’s closest stone.

In Figure 1, one of the stones from team A is closest to the center, so team A earns one point. The other stones are not counted because they are not as close to the center as team B’s closest stone. In Figure 2, team A has the most stones inside the house, but a stone from team B is closest to the center. Therefore, it is team B that scores. Furthermore, since it has another stone closer to the center than team A’s closest stone, team B earns two points for this end.

Curling is sometimes called “chess on ice” because of the strategies involved. There are offensive and defensive methods of play. If your team is to win, you must not only try to place your stones closest to the center of the house, but also prevent the other team from doing so —— and avoid being blocked by your opponent. When your team has last-stone advantage (the “hammer”), it is easier to score points. The hammer belongs to the team that did not score in the preceding end.

Generally, the team with the hammer tries to position its stones around the center of the house so that they can easily place the last stone closer to the center of the house. On the other hand, the team without the hammer often tries to land stones in front of the house to act as a guard.

Because the team with the hammer has the advantage, sometimes the best strategy may be not to score, but rather to end up as the team that throws last in the next end. Let’s see what kind of situation this could be.

An end in which neither team scores is called a blank end. A team that scores even one point gets to go first in the next end and loses the hammer; however, after a blank end, the team that went last in that end gets to go last again in the next end.

Imagine that the eighth end has finished and the score is 3-3. In the ninth end, team A has the hammer. However, the stones are arranged so that they will likely score only one point. What should team A do?

If there is a possibility that the team will score only one point and lose their last-stone advantage, they may change their strategy and keep from scoring for themselves while preventing their opponents from scoring. One strategy would be to knock all of the stones out of the house, resulting in a blank end. By doing so, they can reorganize the flow of the game so that they have the hammer in the final end and try to score at least one point.

In addition to sliding the stone, the other factor that determines the success of a team’s game is sweeping. Before a game, water is sprinkled on the ice to freeze and form particles that make the surface of the ice rougher. Which do you think makes the stone glide more quickly: rough ice with lots of particles, or smooth ice with a slightly melted surface? The answer is smooth ice. The purpose of sweeping is to change the friction on the ice to alter the stone’s path. Before a stone is thrown, the skip looks at where the other stones are located and decides where the team’s stone should be placed. After the thrower throws the stone, the skip calls to the sweepers how to sweep. When a team wants to cause its stone to go farther and straighter, the sweepers must sweep the ice in front of the stone. This makes the stone slide a few meters farther.

People who do not know the sport of curling well may joke that it is not particularly interesting or challenging. When it became an official Olympic sport, there was considerable debate over whether it was worthy of such an honor. However, those who question this need only try it once to see that it requires much more strength than it appears to. It takes a great amount of mental skill as well as physical skill. Curling’s centuries of popularity have created many modern-day fans who can help you understand the appeal of this so-called “chess on ice.”