To measure things, people in all kinds of countries and regions have devised measurements. In order to communicate better with each other about the different lengths, widths and weights, it was important to coordinate all these sizes. There had to be order in the jungle of sizes and units. The International System of Units (SI) provides a solution.
How long is that?
In earlier times, to measure a piece of cloth, it was measured with the cubit. But not every cubit was the same. For example, the Amsterdam cubit was 68.781 of our current centimeters and, for example, the Brabant cubit was 69.438 centimeters. The differences with the Brugger el, the Hague el or the Frankfurt el were even greater, not to mention the Viennese el. Just travel to some city and get ten yards of cloth, and you might have too much or too little. You had to know which type of cubit was measured in, and you also had to hope that your supplier understood those differences. Difficult, then, all those different lengths. Smaller than a cubit? Are we talking about thumbs, inches, or other measurements?
How much does it fit?
To make things more complicated, each size was divided into smaller sizes. How many inches fit in a cubit? How many feet? You couldn’t rely on there being the same smaller sizes everywhere, which would fit into a larger size the same number of times. Do as many thumbs fit in an Amsterdam cubit as in a Brabant or Viennese one? Were those thumbs the same length? In any case, it was clear that it wasn’t really clear…
Standardization
After the French Revolution, the French armies led by Napoleon conquered large parts of Europe. It bothered the French that they had to calculate with different lengths and volumes everywhere. That all had to be possible better. In 1799, the system of all different local measures was replaced by one distance measure: the meter. In addition, a system was devised that each next smaller size fit into a larger one exactly 10 times. For example: 10 decimeters fit in one meter. We call this: the metric system.
Europe and the rest
Because France had taken over power in large parts of Europe, the introduction of the new system with the new unit sizes within the countries on mainland Europe had to be arranged by decree. Despite this, the old mates continued to function for a very long time, of course not officially. This was different in areas outside the French sphere of influence and the introduction of such a ‘French system’ was prevented. That is why today the English and Americans still often work with miles, feet and inches.
SI System
With the internationalization of the world economy, it became increasingly important that as many countries in the world as possible started working with the same dimensions. On October 11, 1960, the International System of Units was introduced, with the French name Système International d’unités , abbreviated: SI . Also for uniformity it is recommended to use the abbreviation SI internationally, in the Netherlands we therefore use: SI system . The system does exactly what the name suggests: a uniform set of sizes is agreed. The standard is managed by the Bureau International des poids et mesures , in Sèvres (France). The SI system builds on the metric system, which was introduced in France in 1799.
Standard or not
Many countries have adopted the SI system, although many old measurements are still used. Consider, for example, the image size of a monitor, or the diameter of a bicycle wheel, both of which are still often displayed in inches for unclear reasons. When you hear older people talking about an ounce of smoked meat or a pound of potatoes, you also hear measurements that do not appear in the SI system.
Not standard, but still allowed
Some sizes are not part of the SI system, but are still recognized under that system. For example, we express temperature in degrees Celsius and not in the agreed SI measure, kelvin. This has everything to do with the citizen’s habituation and the manageability of numbers. It is simply much easier to say that water boils at 100 degrees Celsius than to talk about 283.15 Kelvin. Hours and minutes are also not SI measures, the unit of time is second.
Basic SI system units
The idea behind the standardization is that there is only one basic measure for each physical or chemical quantity. Therefore, for example, the standard of time is the second, not the minute, hour or year. Of course you can display minutes, hours and years in the correct number of seconds. In the table below you see the seven mutually independent basic units, also called basic dimensions.
|
Greatness |
Basic unit (name) |
Basic unit (symbol) |
|
length |
meters |
m |
|
mass |
kilograms |
kg |
|
time |
second |
s |
|
electric current |
ampere |
a |
|
absolute temperature |
Kelvin |
K |
|
amount of substance |
mol |
mol |
|
brightness |
candela |
CD |
To distract
Other SI units can be derived from these basic units. For example, the unit for area is m² (square meter), and the unit for speed is m/s (meter per second). The entire SI system forms a coherent whole. In the Netherlands, the use of this system in professions, trade and education was made legally mandatory in 1978 by the Calibration Act (nowadays this is: Metrology Act).
European Union
The use of the SI system is legally required in the countries of the European Union as the only permitted system. In addition, the use of the old units for mass and length is still permitted in the United Kingdom, although the British government has conducted extensive campaigns to introduce the metric system. However, as long as the old sizes are still allowed, it will be very difficult to get people to work with the new system.
Other appointments
The SI system also includes a series of agreements on the spelling of names and symbols. In addition, the names, prefixes from the metric system, names of (large) numbers and the correct spelling of numbers have been arranged.
How to write numbers
According to the official agreement, large numbers should be grouped into groups of 3 digits, with a short distance between the groups. What you often encounter in Dutch is a dot between the groups of numbers for the sake of readability. So this is incorrect.
Example: 123.345 is incorrect, and should be written as 123 345
On many computers and calculators, a point is used as a decimal separator. According to SI conventions, a comma must be used. Only in English-speaking countries may a decimal point be used.
- In the Netherlands you write: 123.45
- In the Netherlands the wrong number is 123.45
- Large numbers should be written as 123 345.66
- So 123,345.66 is incorrect
The use of points is incorrect because it can cause confusion with the English decimal point.
read more
- Fahrenheit, Celsius and Kelvin
- Measuring, but with what?
- Measuring with meters is knowing
- Prefixes, as defined in the SI system