# The Domino Effect

Dominoes are small rectangular blocks with a square face that is either blank or marked with an arrangement of dots similar to those on dice. Each domino has a unique pattern that makes it distinguishable from other dominoes in the set, and some have numbers printed on them (often in Arabic numerals) to aid in identification. A complete set of dominoes consists of 28 pieces. Dominoes are used for a variety of games, including scoring ones in which players lay dominoes end to end to create lines or angular patterns. Some players use them to create sculptures with the pieces, and others use them as toys.

The word “domino” also has a common metaphorical meaning: a simple action that triggers much greater—and often catastrophic—consequences. Whether it’s a toppling line of dominoes or the domino effect in a story, this concept reminds us of how important it is to think carefully and act deliberately.

Physicist Stephen Morris agrees that the way dominoes fall is like a chain reaction. When a domino is stood upright, it has potential energy, or stored energy based on its position. But when the domino is tipped, most of that energy is converted to kinetic energy—the energy of motion. This energy is transmitted to the next domino, which then provides the push needed to topple it. The rest of the energy travels along the chain, until the last domino falls.

In most domino games, each player takes a turn placing a domino on the table. Depending on the game, this may involve emptying one’s hand while blocking opponents from playing their tiles or calculating points and determining when to stop play. Some games are won by the first player to place all of his or her dominoes. In others, the winning player is the one whose combined sum of all of the spots on his or her remaining dominoes is the least.

Many domino fans enjoy creating mind-blowing setups of dominoes that cascade in spectacular ways. For example, a player might stack dominoes side by side in a long line and then gently tip the first one. This can cause all the other dominoes to fall in a rhythmic and beautiful cascade that forms an intricate design.

To play this game, you need a full set of dominoes (28 of them in a double-twelve or double-nine set). Typically, you start by arranging the dominoes in a line with the matching ends touching. Then you play a tile to the end of the line, ideally a double so that it is touching both the one’s and the two’s and that its exposed dots form a multiple of five (e.g., five to six). Each player then adds a piece to the end of the line and the first player to play a tile whose exposed dots total a multiple of five wins that round. Players continue to play in this manner until someone goes out or the players reach a point where they cannot advance their pieces any further.