UNIT SYSTEMS: CHARACTERISTICS AND CLASSIFICATION - SCIENCE - 2025

A system of units is a collection of units of measure and rules that relate those units to each other. In this sense, systems of units are understood as sets of standardized and uniform measurement units.

Historically the systems of units have played a fundamental role in science and commerce, since they have allowed to regulate and unify multiple concepts. Today, the unit systems have been divided into two large groups: the metric system and the imperial system.

However, it is possible to find other systems of units in the world, such as natural, technical, decimal, cegesimal and Anglo-Saxon, among others. However, most of these systems of units tend to be derived from the same units of measurement, those given by the metric or imperial systems.

Systems of units are also related to other important concepts such as magnitude. This refers to the numerical value that is given to everything that is measured. In this sense, systems of units can measure magnitudes of force, mass, time, area, speed, volume, length, among others.

It can be said that a system of units aims to measure the different existing magnitudes, making use of the same pattern, rules and group of units.

Classification of unit systems

Unit systems were first devised in France in the late 18th century. They are born thanks to the need to be able to count and measure things using the same patterns or conditions.

However, these have evolved enormously over time as the needs of human beings change (fun, 2016).

The first system that was implemented was the decimal metric, however, today we have other examples of unit systems, as can be seen below:

Metric system

Historically, it was the first system of units proposed to unify the way elements were measured and accounted for.

Its base units are the meter and the kilogram, and the multiples of the units of the same type must always increase on a decimal scale, that is, from ten to ten.

This system was initially devised in France and later adopted by all European countries, except the United Kingdom, which decided to stick to its system of units known as the imperial system.

This system has evolved over time, being expanded and restructured to become the international system that we all know today (Alfaro).

Imperial system

The imperial system or Anglo-Saxon system of measurements is a system made up of non-metric units that is currently used mainly in the United States.

Despite being a system devised in the United Kingdom, today it presents certain differences with the old system that was used in the United Kingdom.

For this reason, in the United States it is known as the Anglo-Saxon system and in the United Kingdom it is known as the imperial system.

The units of measurement in both countries receive the same names, however, their numerical equivalences tend to differ in magnitude (need, 2017).

The units of measurement used are the foot, the inch, the mile, the yard, the league, the chain, the furlong, and the rood.

Natural system

Natural units or Planck units was a system proposed by Max Planck in the late nineteenth century in order to simplify the way physical equations are written.

In this sense, it contemplates the measurement of fundamental quantities (length, mass, time, temperature and electrical charge).

It is useful because it allows comparing quantities in a simpler way and eliminates the constants of proportionality from the equations, making their results can be interpreted independently of these constants.

These units are commonly called the “units of god”, since they eliminate the typical arbitrariness of other systems of units previously proposed by human beings (Britten, 2017).

Cegesimal system

The cegesimal system or CGS system is based on the units of centimeter, gram and second. From these three units its name is derived.

It was first raised in the 19th century by the German mathematician and physicist Johann Carl Friedrich Gauss to unify the units used in various technical and scientific fields.

Many physical formulas are easier to express thanks to the use of the cegesimal system, in this sense Gauss's objective was fully achieved and the expansion of a certain technical and physical term became possible in other areas of knowledge.

Over time, this system derived from the metric system, was also adopted by the British Association for Advanced Science (BAAS for its acronym in English and BA today).

International System of Units

The International System of Units or SI is the most popular system of units in the world today. It was adopted as a priority and only by all the countries of the world except the United States, Burma and Liberia.

It is derived from the old decimal metric system, for this reason today it is also called the metric system.

Since 1960, and thanks to the XI General Conference on Weights and Measures, six basic units were established by which the metric system should be governed: second (s), meter (m), ampere (A), kilogram (kg), candela (cd) and kelvin (K). Over time, the unit of mole was also added to measure chemical compounds.

It is a system of units that is based on fundamental physical phenomena. Its units are an international reference that serves as the basis for developing measurement tools and instruments.

These instruments are in constant calibration and comparison to be fully unified (Britannica, 2017).

In this way, the international system has allowed there to be a worldwide equivalence between the elements that are measured, by making use of similar instruments that share the same units.

This is how, regardless of the distance or the place where reference quantities are taken, they will represent the same in any part of the world. Thanks to this, between 2006 and 2009, the international system was unified according to ISO standards.

References

1. Alfaro, LI (sf). Unit I Systems of Units. HIdalgo: Autonomous University of the State of Hidalgo.
2. Britannica, E. (2017). Encyclopædia Britannica. Retrieved from International System of Units (SI): britannica.com
3. Britten, EB (2017). I am learning. Obtained from Unit systems: I'm-learning.com
4. fun, M. i. (2016). Math is fun. Obtained from Metric System of Measurement: mathsisfun.com
5. need, S. and. (2017). com. Obtained from Systems of Measurement - Weights and Measures: skillsyouneed.com.