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Author: S.LAL
Created: 13 Jun, 2009; Last Modified: 29 Apr, 2018

Units and Measurements


Measurements are an integral part of our daily lives. Students, waiting anxiously for a boring lecture to end, very often glance at their wrist-watches, measuring the time remaining to break free! At the vegetable mart, a buyer observes attentively as the seller weighs 2 kilograms of onions on his balance that the buyer had requested for. At an electrical shop, a shopkeeper carefully measures out 3 meters length of electrical wiring for a customer.

Three very important quantities have just been referred to – related to time, mass and length. They have become so fundamental to our everyday lives that we rarely spend a thought on the history of their emergence.

Before we go into that, however, note that any measurement consists of two parts – a number and a unit. For the measure of 15 minutes, “15” is the number and “minutes” is the unit. The number and the unit always go together – separately they lose their meaning.

A very important aspect of a measurement system is that of a common understanding of what, and how much, the units stand for. If the vegetable seller and the buyer did not have a common understanding of how “heavy” a kilogram is, there would only be endless arguments.

Towards Standards

In the early days of human civilisation, units of measurement were adopted for sheer convenience, i.e. easy availability for measurement purposes. The limbs of man themselves became the source for units of length: for example, the “ell” was the distance from the elbow to the fingertips of an extended hand, the “inch” was the width of the thumb at the base, and the “foot” sprang from the length of a man's foot. However, since there were too many variations between individuals, the situation led to constant confusions and controversies

As trade developed between communities, regions and countries, the need for establishing agreements on units of measurement was badly felt. Over a period, local/regional governments started establishing standards to serve as model measures for everyone. It was natural that, with time, different systems would come up regionally/countrywide which would finally battle with each other as the standardisation process became a global effort.

A standard refers to a government designated physical object on which a unit of measurement is based. Measuring devices are then manufactured based on the standards. Thus, there is a standard for measuring length called the meter, which is based on a platinum-iridium bar (kept at the Bureau of Weights and Measures in France) having two marks designating the standard distance of one meter. Measuring devices like the meter sticks used in school were manufactured from permanent models which themselves were based on the standard meter in France.



Landau, LD & Kitaigorodsky, AI, Physics for Everyone – Physical Bodies, Book 1, 4th edn, Moscow: Mir Publishers, 1980.