The domino effect is the phenomenon of one thing knocking over another in a chain reaction. It can be seen in many different ways — for example, a person dropping a single domino tile on a pile of bricks that cause the entire stack to tumble over. But this chain reaction can also happen in a much larger scale. This is what physicist Lorne Whitehead discovered in 1983 when he used the power of gravity to demonstrate that a domino can knock over objects about a third of its own size.
Dominoes are small rectangular tiles that each contain a number of spots or dots. The most common set contains 28 unique tiles, with each domino having a number on each of its two sides. These numbers represent the results of throwing two six-sided dice (the dominoes are sometimes called bone, or peg, tiles).
In most games, a player takes turns placing a domino edge to edge against another in such a way that the adjacent faces match, or are identical and form some specified total. The first player to complete this process scores the points or wins the game. A variety of games can be played using the same set of dominoes, and a number of rules exist for each of these.
Originally, dominoes were made from natural materials such as bone, silver lip ocean pearl oyster shell (mother of pearl), ivory or a dark hardwood such as ebony. They may have been painted or inlaid with black or white pips. Today, domino sets are often made of polymer, such as melamine, or plastic. Some sets are still made from natural materials, however, and have a heavier weight and feel to them than their polymer counterparts.
Each domino has a specific number of spots on its face that distinguishes it from other dominoes. These spots are usually arranged in a pattern, such as a zig-zag line or a star, and each domino has the same number on both its left and right side. Dominos with a combination of the pips on both of its sides are known as doubles.
The number of pips on each half of a domino face determines what type of domino it is. The most commonly used domino is a double-six, which has six pips on each of its two sides. Other types of dominoes include double-blank, which counts as 0, and double-zero, which has no pips at all.
In the Western world, dominoes were first recorded in use in the mid-18th century. In contrast, Chinese dominoes appear to have developed in the 12th or 13th century. These were functionally identical to playing cards and differed from the traditional European domino sets in that they only represented each of the 21 possible results of throwing two six-sided dice, and did not have blank or matching faces. They were also longer than typical European dominoes. These differences were probably due to the fact that Chinese dominoes were initially made to serve as an alternative to gambling and gambling-like activities in regions where there were religious proscriptions against playing cards.
