# The Basics of Dominoes

A domino is a small tile marked on both sides with an arrangement of spots, or pips, like those on a die. Each domino is usually twice as long as it is wide, making it easier to stack the pieces after use. The tiles are used in a variety of games, both blocking and scoring. Dominoes can also be used to construct elaborate patterns, and have even been employed in theatrical presentations to illustrate scientific concepts.

When one domino hits another, the latter becomes a trigger for a chain reaction that can knock over objects of about a half their size or more, as University of British Columbia physics professor Lorne Whitehead demonstrated in 1983. He used 13 dominoes to create a chain reaction that included three-dimensional shapes, such as an arch, a circle, and a pyramid.

Most dominoes are used for positional games, in which players place a domino edge to edge against another, either identically patterned or forming some specified total. The identifying mark on each side of a domino, called a pip, may be any one of the numbers from 1 to 10, or it may be blank or marked with a line or ridge to divide it visually into two squares. Each of these squares is valued by the number of pips on its opposite side; a double is always valued higher than a single, regardless of the identifying marks on its face.

The rules of a domino game determine how the pieces are played, including the order in which they are placed on the table and the sequence of play. The player with the heaviest tile in his hand, referred to as the setter or downer, makes the first play, depending on the rules of the game. In some games, the player may choose to buy a domino from the stock (see “Passing and Byeing” below).

Once the line of play is established, it is possible to build up complicated patterns of dominoes. The most complex arrangements are constructed to be the starting point for a chain reaction, such as one that will eventually produce an entire structure built of dominoes. The most famous of these is the 206-piece “Las Vegas” pattern, which was created by a team led by a domino artist named John Martin.

Dominoes have inertia, a tendency to resist motion unless an external force is applied to them. This resistance can be overcome with the right nudge, however. In the case of Hevesh’s intricate setups, a tiny nudge can be enough to tip a huge assemblage over.