How Do Dominoes Work?

When Lily Hevesh was a kid, her grandparents gave her their classic 28-piece set of dominoes. She loved to create a long line of them and then flick the first one, starting a chain reaction that would send every other piece falling. It was a lot like the way nerve impulses fire in the brain and then travel down an axon, creating larger consequences from something smaller. It’s an idea that led to a well-known phrase: the domino effect.

But dominoes are more than a simple toy. They can also be used to build complex structures and make artistic designs. And the laws of physics play an important role in how they work.

For Hevesh, the key is gravity. She says it’s the force that makes her intricate arrangements possible. When a domino is knocked over, it’s propelled down the line toward the next domino and then the surface below it. But it also gets a little help from friction. As the domino slides down its row, it rubs against the bottom of the next domino and the surface below that. That creates heat, which transforms some of the domino’s kinetic energy into sound and other forms of energy that can push or pull on the next domino in line.

That’s why the best way to make a domino chain is to place the pieces one at a time so that their matching ends are touching and pointing in the same direction. Then, when you play a tile to the end of that domino chain, it must be placed perpendicular to the double or else the domino chain will develop a snake-like shape.

Dominoes can be made from many rigid materials, including bone (usually from a cow), silver lip ocean pearl oyster shell (mother of pearl), ivory and a variety of dark woods such as ebony. But plastic is by far the most popular because it’s durable and inexpensive. A few manufacturers offer sets in other natural materials, such as stone; metals, such as brass and pewter; ceramic clay; and frosted glass or crystal. But those sets tend to be more expensive than those made from polymer.

The number of dominoes in a set is limited by the fact that each one must have either identical or matching pips on all four sides. Consequently, most sets are “extended” by adding additional ends with more pips to increase the total number of possible combinations of adjacent pairs. But even in an extended set, it’s possible to run out of pieces.

The earliest written references to domino are in the mid-18th century, but the word probably has roots that go back much further than that. In both English and French, it referred to a long hooded cloak worn with a mask, or to the black domino that contrasts with the white surplice of a Catholic priest. The latter sense may have influenced the design of the domino, with its contrasting black and white surfaces.