A zipper has three parts

The Metric System

People all over the world use grams, kilograms (kilos), meters, and liters. These are all ways to measure things. They are all part of the metric system. During the French Revolution (1789-1799) against the king, the revolutionary government started the metric system. Before that, every part of France had a different system for measuring things. Also, cloth makers measured cloth with one system. Jewelers used another system. Carpenters used another. Other countries used different systems. The revolutionary government wanted one scientific system of measurement. They asked a group of scientists and mathematicians to invent a system.

The mathematicians and scientists decided to use the numbers ten, hundred, and thousand for their system.

Next, they had to decide on a "natural" length. They chose one ten-millionth (1/10,000,000) of the distance from the equator to the North Pole. They called this distance the meter. Then they chose the gram for weighing things. A cubic centimeter of water weighs 1 gram.

Mathematicians and scientists worked for 20 years until they finally had a complete measuring system. The biggest problem was measuring the meter.

The metric system was a wonderful gift to the world. There are only a few countries that don't use it. The United States is one. The metric system is truly an international system.