On September 23, 1999, NASA scientists lost the $100 million Mars Climate Orbiter because they instructed the craft in imperial (inches and feet) instead of metric (metres) measurements. It sent the probe, which was set up for metric data, off course and burning up in the Mars atmosphere.

The first decimal system was introduced in the 4th Century BC by the Sumerians of Mesopotamia, to whom the invention of writing is credited. They based their numerical system on powers of 60 subdivided into multiples of 10. It was from this system that Sumero-Babylonians developed the time system that we use today: each hour is divided into 60 minutes, which are divided into 60 seconds. However, they did not have a symbol for zero, which was introduced by Arabians only toward the end of the first millennium BC. It is thought that the zero could have been devised by Indian Hindu mathematicians because the concept of nothing was important in their early religion and philosophy.

**Metric system introduced into Europe**

In 1202, Italian mathematician Leonardo of Pisa – better known as Fibonacci – explained the decimal system to his European colleagues in his Book of the Abacus. Fibonacci’s father was a customs officer in the North African town of Bugia, so Fibonacci grew up with the Moor education of the decimal system. English mathematician John Halifax would try to promote the decimal system to his countrymen in 1253. But it was only in the 16th Century that Simon Stevin, a quartermaster in the Dutch Army, presented the Western world a user-friendly way to convert to decimal fractions in his book “The Tenth” published in 1585.

In 1670, Gabriel Mouton, a theologian and mathematician from Lyon, France proposed the general use of the decimal system and suggested a standard linear measurement based on the length of the arc of one minute of longitude on the Earth’s surface and divided decimally (by ten). A “metre” was defined as 1/10,000,000 of the distance on the earth’s surface between the equator and either pole. Later the meter was redefined as the distance between 2 scratches on a bar of platinum-iridium alloy. In 1960, the meter was established in terms of an atomic standard, redefined in wavelengths of light. The metric system was given the official symbol SI for Systeme International d’Unites, the “modernised metric system.”

**Decimal system used in most countries**

The decimal system is used in most countries, but not the USA. The system was made legal (but not mandatory) in the US by the Metric Act of 1866, and the US also was a signatory of the Treaty of the Metre in 1875. The US Congress passed the Metric Conversion Act of 1975 (Public Law 94-168) and established the US Metric Board – also see US Metric Association – but did not set a target date for metric conversion. However, US companies are gearing toward the metric system, with all 4 major motor companies converting to the metric standard. The computer industry also uses the decimal system: your computer operates on the binary calculations of 1 and 0.

Interestingly, standardization of the inch for worldwide use occurred only in 1958. (The inch was standardized worldwide as 25.4 millimeters exactly.) Prior to that the United States, Great Britain, and Canada each had their own definition of the inch, and in each case the inch was defined in terms of metric units, the only set of internationally-accepted measurement standards. A problem still exists for the foot, where the international foot (based on the 25.4 mm inch) and the survey foot (based on the 25.40005 inch) are both in use. Over 100 miles they differ by 32 cm, or over one foot.

Simon Stevin published “The Tenth” in 1585

The mile comes from the Latin “mille passus”, based on the Roman Legion’s 1,000 paces.

“Decimal” is the Latin word for “ten.”

The word “metre” was adopted only in 1793 by the French Academy of Science, derived from the Greek word “metron”, meaning “a measure.” The metric system was adopted officially in France in 1799.

A study by Richard Phelps of the Pelavin Research Center of the American Institutes for Research declares that a transition to metric usage in the US would be a major factor in correcting the poor performance by US students in math and science.