# Physicists Explain How Dominoes Work

Dominoes are small, flat, rectangular blocks used as gaming objects. They are also known as bones, men, pieces, or cards. They are normally made of rigid material such as wood, bone or plastic. A domino has one or more pips (or numbers) on its ends that are arranged in a specific pattern. Most commonly, each domino is arranged so that its exposed pips touch others on adjacent dominoes or form certain totals (e.g., three’s touch two’s). There are many ways in which dominoes can be combined to form games and chains of dominoes.

Lily Hevesh began playing with dominoes as a child, using her grandparents’ 28-piece set. Her fascination with the little square tiles grew into an obsession, and she has since created a popular YouTube channel where she posts videos of her spectacular domino creations.

While Hevesh isn’t a professional domino artist, she still relies on physics to create her chain reactions. She believes the key to her success is understanding what makes a domino fall.

Physicist Stephen Morris agrees. He explains that when a domino is standing upright, gravity exerts an upward force on it, causing it to push on other dominoes. “As it’s pushed on, the potential energy stored in that first domino is converted to kinetic energy—the energy of motion,” he says. “As kinetic energy builds up, that energy pushes on other dominoes until they fall.”

As Hevesh plays with her dominoes, she notices that each time she places a new tile, it must be positioned so that its matching ends are touching. Then, if the exposed pips on the two touching ends match—one’s touch two’s or five’s touch five’s—the player scores points.

This basic game can be played with just about any type of domino set. However, larger sets—called extended—are available that increase the number of possible combinations of ends by three. Common extended domino sets include double-nine (55 tiles), double-12 (91 tiles), and double-15 (136 tiles).

In addition to blocking and scoring games, players can play positional games. In these, players take turns placing a domino edge to edge with another. When a player cannot place a domino, they “knock” or rap the table. Play then passes to the next player.

Dominoes are normally twice as long as they are wide, which allows players to move them more easily. They can be repositioned by simply sliding them or flipping them over, and they are often arranged in rows with gaps between each row of dominoes.

Some players choose to keep a record of the number of spots on their remaining dominoes, called a chip count. Then, when a player chips out—plays all of their remaining dominoes—the winning player is the partner with the lowest chip count. A domino game is a fun way to pass the time and to exercise problem-solving skills. However, some players feel that the game can be too monotonous and repetitive. That’s why some people prefer to add complexity by incorporating rules that require more than just one or two players to play.