The SI System

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International System (SI)

In 1875, the &ldquo;Metre Convention&rdquo; mandated the establishment of a permanent International Bureau of Weights and Measures andthe Decimal System for working out related units.

The different magnitudes were worked out as per the decimal system and given standard names. The current nomenclature is given below.

The SI is intended to be an evolving system; units and prefixes are created and unit definitions are modified through international agreement as the technology of measurement progresses and the precision of measurements improves. For example, the most recent derived unit, the katal, (an unit for measuring catalytic activity of enzymes) was defined in 1999.

We have to be careful about using the correct case (upper/lower) and they could mean different units.

As of now the SI has been adopted by all countries except the United States, Liberia and Myanmar

Non Decimal Systems

Many other unit systems have developed over time and do not follow the decimal system. They have got so entrenched in our life &amp; language that they have not been changed. Some examples are given below.

Time – Second, Minute, Hour, Day, Week, Month, Year. Higher units like Century &amp; Millenium follow the decimal pattern.

Byte – Due to technical reasons, the units for Information follow a system based on 8. 1 Byte = 8 Bits. 1 Kilobyte = 1024 bytes.

Distance – Inter-stellar distances use the &ldquo;light year&rdquo; to measure distances between stars &amp; galaxies. A &ldquo;Light Year&rdquo; is the distance travelled by light in one year.

Angles – The unit of angle measure is Radians in the SI system. It is not a basic unit but a derived unit.

We will look at the course which measurement may take in the future.

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