Story of Measurement 1

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Counting– One of the earliest inventions were numbers which helped compare collections of discrete objects. Initially each group may have had its own system of counting.

Time – the measurement of time is so intimately involved with the history of humans that we would deal with in the next chapter.

Temperature – until 3 centuries ago, the measurement of temperature was very crude.

The modern invention of the unit of measurement of temperature depends on the physical fact that pure water freezes of boils anywhere in the world (at the same altitude) at the same temperature. Hence the freezing temperature of pure water at sea level was taken as 0 and the boiling temperature was taken as 100. These are purely arbitrary numbers given keeping the decimal number system in mind. The unit was called Degrees Centigrade, the name referring to its relation with the decimal system.

Another unit to measure temperature unit had been developed earlier, to measure the temperature of the human body called Fahrenheit.

Length–Various civilizations developed various measures of length related walking and riding on animals. The name &ldquo;foot&rdquo; is a reminder of this relation. In the 19thcentury, most countries decided to accept the meter as a unit for length.

Area– was initially defined possibly in terms of a land measure related to ploughing.

Initially are was seen as an independent idea. Terms like &ldquo;ground&rdquo; &amp; &ldquo;acre&rdquo; are remnants of this idea. Later area was seen as an extension of length. The unit of area was taken as the area of a square with its side being a unit of length.

The square shape was probably chosen because it could be drawn given just one dimension; that of the side. It is a shape which can be replicated anywhere very easily. Square is also a shape which tessellates any area without leaving any gaps.

Any polygon could be divided into triangles, which in turn can be converted to rectangles of the same area and the rectangles could be expressed in terms of unit squares. It was natural to call the area units in terms of &ldquo;squared&rdquo; – SqCm, SqM etc. We will see more about measuring areas in the section on mensuration.

Volume – was possibly defined in terms of the quantity of water which a normal person could drink. Terms like Pint &amp; Gallon possibly came out of this understanding.

Later the definition of volume was seen as a natural extension of the measurement of area. The unit of volume was taken as the volume of a cube whose side is one unit of length. The unit of volume was a Cubic Mt which is a cube with 1m edges. They were subdivided into Cubic Cms.

Since a cubic mt was too large a volume for daily transactions, the common unit of volume was a Litre. A litre was equal to 1000 cubic cms. A cubic mt was equal to 1000 litres. A cubic cm was a milli litre.

Volume &amp; Capacity

In our daily life we also need to differentiate between volume and capacity. Volume is that of the material out of which an object is made. Capacity refers to the volume of solids or liquids that an object can hold.

For example, a cylinder made of solid iron cannot be used as a container. Hence it has volume but no capacity.

But a hollow cylinder has volume and also has the capacity to hold a liquid. Its capacity is nearly equal to the total volume of the cylinder. But in most cases the term volume is used to denote capacity. For example, a math problem may just ask for calculation of the volume of a cylinder. The exact meaning has to be understood from the context of the problem.

< 24.1 Understanding Measurement | Topic Index | 24.3 Measurement of Time >