A flat thumbsized, rectangular block that is usually twice as long as it is wide and bears from one to six pips (dots or spots) on its two face parts. 28 such dominoes form a complete set. Dominoes may be used for games in which players try to build lines of dominos that end with a single piece, or they may be used as toys that are stacked on end in long lines. The most common games use a double-twelve or double-nine set. When a player has no more dominoes to play, she “chips out” of the game. The other player then chooses a domino from the boneyard, and the next person plays that piece. In these games, the value of a domino is its rank or weight. The higher the ranking, the more valuable a domino is.
Lily Hevesh started collecting dominoes when she was 9 years old, and her grandparents gave her a classic 28-piece set. She loved setting up the dominoes in straight or curved lines and flicking the first one to make them all fall down. She started making videos of her creations and attracting followers on YouTube, where she now has more than 2 million subscribers. Hevesh has also built domino structures for movies, TV shows, and events—including a Katy Perry album launch.
Physicist Stephen Morris agrees that dominoes have inertia and can resist movement until a force pushes or pulls on them. He says when a domino is standing upright, its position gives it potential energy—stored energy based on its height and its relationship to other dominoes around it. As soon as a domino is pushed, however, the potential energy turns to kinetic energy—energy of motion—and the other pieces begin to topple, too.
Dominoes can be used for games in which players try to stack pieces on the edge of a line to block other pieces, or they can be used to score points in a game of skill. A variety of other games, often adaptations of card games, are played with dominoes. Some of these games were once popular in areas where religious prohibitions against playing cards made cards difficult to acquire.
Another type of domino game is a chain reaction, in which players take turns choosing a domino to play. Each player has to have a domino with a matching value to the last domino played before they can continue the sequence. Dominoes are often arranged in rows and columns to create an elaborate pattern, and the winning combination is the one that completes this pattern. Chain reactions can be simple or complex, but the more dominoes that are in the line, the more difficult it is to predict how they will all fall. That’s what makes these sequences so exciting to watch.