What is metric

"My height is 180 cm, and my weight is 70 kg."
"Now it is 15°C here, and the maximum is 25°C."

Words like these said by everyone all contain such units: m, kg, °C, etc. As we all know, these units belong to SI, which is the modern form of the metric system. But do you know what metric system is? And how the metric system was created and developed?

The metric system is an internationally agreed decimal system of measurement that was originally based on the mètre des Archives and the kilogramme des Archives introduced by the French First Republic in 1799. Now it's used everywhere in the world.

The metric system was first developed during the French Revolution to replace the various measures used at that time. On the eve of the French Revolution, France had an estimated quarter of a million different units of measurement. In many cases the value of a unit differed from town to town and even from trade to trade even though they might have the same name. While certain standards, such as the pied du roi (the King's foot) had a degree of pre-eminence and were used by savants (scientists), many traders used their own measuring devices. This gave scope for fraud and hindered commerce and industry.  So People needed to take measures to replace this confusion with a radical new system with fixed values.

The first practical implementation of the new system was the system implemented by French Revolutionaries towards the end of the 18th century. Its key features were that:

• It was decimal in nature.
• It derived its unit sizes from nature.
• Units that have different dimensions are related to each other in a rational manner.
• Prefixes are used to denote multiples and sub-multiples of its units.

These features had already been explored and expounded by various scholars and academics in the two centuries prior to the new system being implemented.

Between 1795 and 1800, during the French Revolution, and with the backing of Louis XVI, the system of weights and measures was totally reformed. The new system of measures had a rational mathematical basis and was part of the radical effort to sweep away old traditions and conventions and replace them with something new and better.  The French philosopher, the Marquis de Condorcet, who was one of those entrusted by Louis XVI to overhaul the system of measurement, characterized the new system as "for all people for all time".

The key units of the republican measures system were:

• The mètre - the unit of length, defined as one ten-millionth of the distance between the North Pole and the equator on the meridian passing through Paris.
• The are - for land area, defined as the area of a square with sides of length 10 metres
• The stère - for volume (particularly of stacked  firewood), defined as 1 cubic metre
• The litre - for dry and liquid volume, defined as the volume of a cube with sides of one-tenth of a metre
• The gramme - for weight, defined as the weight of a cube of pure water with sides of one-hundredth of a metre and at the temperature of melting ice.

From the beginning, French people were not used to the new decimal system. Until 1840 France reinstated the decimal system and called it "metric system".

The metric system developed as the understanding of science and in measuring techniques has advanced. In 1875 the Convention of the metre was signed and control of the metric system passed from France to a trio of inter-government organizations headed by the CGPM and based in Sèvres, France. In 1960, at the 11th conference of the CGPM, the metric system was overhauled and the resultant system named "The International System of Units (SI)". The driving force behind the metric system was the need for a single, rational and universal system of weights and measures that could be used world-wide.

Here are some SI units in our everyday life:

Length: m

Mass: kg

Time: s

Temperature: °C

Potential difference: V

Energy: J

Power: W

Pressure: Pa

In this blog, we talked about what metric system is, and how the metric system was created and developed. In the next blog we will talk about SI (International System of Units).