Metrication

Metrication, or metrification, is the process of converting from the various other systems of units used throughout the world to the metric or SI (Système International) system. This process was begun in France in the 1790's and spread over the following two centuries to all but four countries, representing 95% of the world's population. The process was completed in most of the world in the 19th and early 20th centuries, replacing numerous historical weights and measures. The countries of the former British Empire completed metrification during the second half of the 20th century, with Ireland recently completing metrication on 20th January 2005. Today only the UK, U.S., Liberia and Burma (Myanmar) have not fully metricated, although Liberia and Myanmar use it in practice and the UK is currently in the process of conversion. Only France, the US, UK and Japan saw any large scale popular opposition to metrication, the main objections being based on tradition, aesthetics and distaste for a 'foreign' system.

Exceptions

There are three main exceptions to the metrication trend; the UK, US and global air and sea transport industry. Contary to popular belief, the US and UK do not use a common system (see Imperial unit and U.S. customary units for details). With the exception of the inch which was standardised at exactly 2.54 cm by an internation conference in 1958, most other units differ in value in the US and UK. A gallon of liquid for example, is 3.7 L in the US but 4.5 L in the UK. The US also has a dry gallon, which is 4.4 L.

Related Topics:
Imperial unit - U.S. customary units - Inch - Gallon

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The UK made initial moves to convert to metric as long ago as 1862, when the Select Committee on Weights and Measures favoured the introduction of decimalisation to accompany the introduction of metric weights and measures http://www.dti.gov.uk/ccp/topics1/pdf1/met1862.pdf. The country finally decimalised their currency a century later in 1971. There is a good deal of public resistance to metrication, which is seen by many as the imposition of a foreign system and to be connected with other unpopular ideas from mainland Europe, such as the EU and the Euro. There has been partial progress, however; metric units have been taught in UK schools since the late 1960s, and certain industries also converted or largely converted decades ago. For example, the paper industry converted in 1970 and the construction industry between 1969 and 1972 — although certain products continue to be produced to imperial sizes but with metric size descriptions, for example, as 13 mm (rather than as half-inch) thick plasterboard. However, many consumer products are still sold in traditional units. In August 2005 the European Union announced it would require Britain to set a legal deadline for the completion of metrication. http://www.guardian.co.uk/eu/story/0,7369,1558081,00.html

Related Topics:
Select Committee - Decimalisation - EU - Euro - Paper - Construction - Plasterboard

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:See also: Metrication in the UK

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The United States remains the main exception. Although Thomas Jefferson recommended metrication and currency decimalisation (The US was the first country to have a decimal currency) and metrication is the official policy of the American government since the Convention du Mètre (Metre Convention), and several laws encourage or require use of metric units in various contexts http://lamar.colostate.edu/~hillger/laws/index.html, the progress of metrication has been much slower in the United States than in the rest of the world. Non-metric units continue to be predominantly used in everyday life, and in commerce, engineering, and aviation. However, change has occurred, with most products within the U.S. now required by law to be labelled with both metric and non-metric units, and a number of companies and government agencies switching to metric standards.

Related Topics:
Thomas Jefferson - Convention du Mètre - Engineering - Aviation

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One peculiar example of this is bottled soft drinks, commonly sold in units of two litres, and with units of 500 mL, one litre, and three litres being less, but increasingly, common. This is a result of the introduction of PET bottling technology coinciding with a particularly strong metrication push in the mid to late 1970s; consumers found that they could buy a two-litre plastic bottle of their favourite soft drink more cheaply than they could four one-pint glass bottles, and the convention stuck. Smaller units, however, continue to be sold more often in fluid ounces, such as 8-ounce (240 mL) and 12-ounce (355 mL) aluminium cans and 20-ounce (591 mL) PET bottles.

Related Topics:
Soft drink - PET

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The United States continues to use only miles for road distance signs, with the exception of Interstate 19 in Arizona. Originally U.S. legislation set October 2000 as a deadline by which states must undertake construction work and statistics in metric for states to be eligible for federal funding, but that requirement has since been rescinded. Some states, such as California, have experimented with dual-unit signs, particularly near the borders with Canada and Mexico, but there are as yet no plans for large-scale conversion. There is presently little political support for a comprehensive switch to the metric system.

Related Topics:
Mile - Interstate 19 - Arizona - October - 2000 - California - Canada - Mexico

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Famously, use of two different systems was the contributing factor in the loss of the Mars Climate Orbiter. The manufacturer of the spacecraft had designed the navigation system to be programmed in U.S. customary units measurements, whereas the navigation team at NASA's Jet Propulsion Laboratory in Pasadena, California, controlled the spacecraft using metric units. The multi-million dollar spacecraft crashed into Mars.

Related Topics:
Mars Climate Orbiter - U.S. customary units - NASA - Jet Propulsion Laboratory - Pasadena, California - Mars

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:See also: Metric system in the United States and Fair Packaging and Labeling Act

Related Topics:
Metric system in the United States - Fair Packaging and Labeling Act

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Liberia and Myanmar have not "officially" adopted everyday use of the metric system. Despite the lack of "official" adoption of the metric system in Liberia and Myanmar, unofficial metrication has taken place there, and the economies of these two countries do primarily operate using the metric system.

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Some industries have resisted metrication. Non-metric measures in air and sea transport retain worldwide dominance. In these areas the nautical mile (1.852 km) is preferred over the kilometre, because it closely represents a minute of arc of the circumference of Earth. While the metre was also based on the Earth with 100 km equal to an arc of 1 gon, those units of angle have not seen widespread use, though they do appear on some maps. The gon is a recent name for what is still also called a grad or grade; thus kilometre : centigrade : : nautical mile : minute of arc.

Related Topics:
Nautical mile - Gon

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The knot, which is nautical miles per hour, remains the prime unit of speed for maritime and air navigation (although before the 1960s, statute miles per hour — which bear no relationship to the Earth — were most often used for this purpose, and they remained in fairly common use for some purposes into the 1970s and later). For aircraft flying, altitudes are usually estimated based on air pressure values and described in nominal feet rather than nominal metres. Since aircraft pilots and air traffic controllers in some regions have long been trained to use non-metric units, the potential threat to air traffic safety is sometimes said to be a reason for not fully adopting metric units. However, the ICAO does not support the view that there is a hazard inherent in metric units. In fact, it is ICAO stated policy to standardise on SI units. Several countries and air forces (mainly, but not only former Warsaw Pact) use metres for altitude.

Related Topics:
Knot - Statute miles per hour - Air traffic controller - Warsaw Pact

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