History of measurement facts for kids

Detail of a cubit rod from ancient Egypt, now in a museum in Turin.

Imagine a world without rulers, scales, or clocks! For thousands of years, people have needed ways to measure things. The first measurement systems appeared around 3000-4000 BC. Early civilizations used them for farming, building, and trading goods.

At first, each town or region had its own unique ways to measure. They had different standards for length, area, volume, and weight. Sometimes, the way you measured grain was different from how you measured liquids. As people started making more things and trading across the world, everyone needed to agree on standard measurements.

From the 1700s onwards, scientists began creating simpler, more exact measurement systems. This new science of measurement is called metrology. Even the discovery of electricity helped push for worldwide standard units.

Ancient Measurement Systems

The very first organized ways of measuring things came from ancient Egypt, Mesopotamia (modern-day Iraq), and the Indus Valley (parts of Pakistan and India). This was around 4000 to 2000 BC.

Early records from Babylonia and Egypt, and even the Hebrew Bible, show how people measured. Length was often measured using parts of the body, like the forearm, hand, or finger. Time was measured by watching the sun, moon, and stars.

To measure how much a container could hold, people would fill it with plant seeds. Then they would count the seeds to find the volume. When weighing things became possible, seeds and stones were used as standards. For example, the carat, still used for weighing gemstones, came from the carob seed.

How Units Changed Over Time

Measuring Length

The Egyptian cubit and the Mesopotamian cubit are some of the oldest known length units. They were used around 3000 BC. In ancient India, units like the dhanus (bow) and yojana were common.

A common cubit was the length from your elbow to the tip of your middle finger. It was divided into smaller parts:

• A span: half a cubit (from thumb tip to little finger tip).
• A palm: one-sixth of a cubit (width of the hand).
• A digit: one twenty-fourth of a cubit (width of a finger).

The Royal Cubit in Egypt was a special cubit. It was a bit longer, used for building huge structures like pyramids.

Units like the inch, foot, and yard developed from these older units. The ancient Greeks and Romans learned about the foot from the Egyptians. The Roman foot was about 29.6 cm. It was divided into 12 unciae (inches) or 16 digits. The Romans also used the mille passus (1000 paces), which was about 1480 meters. This became the Roman mile.

When Elizabeth I was Queen of England (1558-1603), she officially changed the mile to 5280 feet (about 1609 meters). This is still the length of a mile today.

The yard (about 0.9144 meters) came into use later. Its exact origin is not fully known. Some think it was based on the double cubit. The early yard was divided into halves, quarters, and smaller parts. Stories say it was based on the distance from King Henry I's nose to his thumb, but this was likely just a way to standardize it.

Here are some old English length units:

Measuring Mass

The grain was the very first unit of mass. It's the smallest unit in many old systems. A grain was originally the weight of a single grain of wheat or barley. It was used to weigh precious metals like silver and gold.

Larger units were developed, often preserved as stone standards. The pound came from the ancient mina unit. Smaller units included the shekel, and larger ones the talent. These units varied in weight from place to place. The Babylonians had a system where 60 shekels made a mina, and 60 minas made a talent.

The carat, used for gemstones, came from the carob seed. It was later standardized to 0.2 grams.

Over time, different "pounds" developed. The "troy pound" (about 373.2 grams) was used in England and the US for money. It had 12 ounces. The "avoirdupois pound" was heavier and used for general goods. It was likely based on the weight of water, which is heavier than grain.

Britain also used larger units like the stone, quarter, hundredweight, and ton. Today, only the stone is still commonly used for measuring a person's body weight. A stone is 14 pounds (about 6.35 kg).

• A "long ton" is 2240 pounds (about 1016 kg).
• A "short ton" is 2000 pounds (about 907 kg).
• A "tonne" (t) is a metric ton, equal to 1000 kg.

Measuring Time and Angle

The idea of dividing a circle into 360 degrees, and a day into hours, minutes, and seconds, comes from the Babylonians. They used a number system based on 60. The 360 degrees might have been linked to their calendar, which had 360 days. Other ancient cultures had different ways of dividing the day and the year.

Towards the Metric System

The metric system uses decimal numbers, meaning it's based on units of 10. This makes calculations much easier! While people in India used decimal numbers for math a long time ago, it was Simon Stevin in 1585 who first suggested using them for everyday things like money and measurements.

Later, in 1670, Gabriel Mouton proposed a new system. His basic unit of length would be based on the Earth's size. He also suggested using prefixes (like "kilo-" or "centi-") for different sizes of units, similar to how the metric system works today.

In 1790, Thomas Jefferson in the United States suggested a decimal system for money and measurements. He wanted a "foot" unit based on a pendulum's swing. His ideas were very advanced for the time.

The Metric System Takes Over

The metric system was first described in 1668 and officially adopted by France in 1799. Throughout the 1800s and 1900s, it became the main measurement system worldwide.

Many countries, including the United States, China, and the United Kingdom, still use some of their older units. However, many of these older units have been redefined to fit with the metric system. For example, the Scandinavian mile is now exactly 10 kilometers. The Chinese jin is now 0.5 kilograms. This helps make trade and communication easier around the globe.