Measure Up: The Length Edition Quiz

The centimetre (cm) is a unit of length in the International System of Units (SI), representing one hundredth of a metre, with "centi-" as the SI prefix denoting a factor of 1/100. This unit was originally the base unit of length in the now deprecated centimetre-gram-second (CGS) system of units. While SI prefixes like milli- and kilo- are often preferred for technical use, the centimetre remains a practical unit for everyday measurements such as human height.

The centimetre finds utility beyond measuring length, including its use in reporting rainfall levels measured by a rain gauge, measuring capacitance in the CGS system, making scale conversions on maps, representing the second moment of areas and serving as the inverse of the Kayser, a non-SI metric unit of wavenumber. In the context of wavenumber, 1 kayser is equivalent to 1 wave per centimetre, while the SI unit for wavenumber is the inverse metre.

The inch, symbolised as "in" or double prime ("), is a unit of length in both the British Imperial and United States Customary systems of measurement. It is equal to 1/36 yard or 1/12 of a foot. The word "inch" has also been used to translate similar units in various measurement systems, often related to the width of the human thumb.

Standards for the exact length of an inch have varied, but since the adoption of the international yard in the 1950s and 1960s, the inch has been defined as precisely 25.4 mm in the metric system.

The term "inch" comes from the Latin "uncia", meaning "one-twelfth" (of a Roman foot). It is related to "ounce", reflecting its origin in Anglo-Norman "unce" and "ounce". In many European languages, the word for "inch" is related to or derived from the word for "thumb".

The inch is widely used as the common unit of length in the United States, Canada and the United Kingdom. It is also used in Japan for electronic parts and is informally used in continental Europe for display screens. In the United Kingdom, the inch is a primary unit for road signs, and its use is permitted for other measurements that follow metric measurements.

The foot is a unit of length in both the British Imperial and United States Customary systems of measurement, symbolised as "ft" or a single quotation mark ('). It is commonly used alongside the inch and the yard. One foot is 12 inches, and one yard is three feet. Historically, the foot has varied in length in different local systems, including Greek, Roman, Chinese, French and English. It typically ranged from 250mm to 335mm, often divided into 12 inches or 16 digits.

While the international foot is widely accepted, the United States is the only industrialised country that prefers it to the metre. In the United Kingdom, the foot is legally recognised and road signs must use imperial units, although distances are indicated in miles or yards, not feet. Canada recognises the foot as an alternative unit of length derived from the metre, although both countries have partially metricised their measurement systems.

The historical origins of the foot include its use in various ancient systems such as Greek, Roman, Egyptian and Gaelic. The length of the international foot corresponds to a human foot with specific shoe sizes. The 1959 International Yard and Pound Agreement defined the foot as exactly 0.3048 metres, 2 ppm shorter than the previous US definition and 1.7 ppm longer than the previous British definition. The UK adopted the international yard in 1964, and the US survey foot remains relevant in surveying despite efforts to phase it out from 2023.

The yard, denoted "yd", serves as a unit of length in both the British Imperial and US Customary systems, equivalent to 3 feet or 36 inches. Internationally standardised since 1959 as exactly 0.9144 metres, 1,760 yards make up 1 mile. The term "yard" derives from Old English, where "gerd" referred to branches, staves and measuring rods. Initially used in the context of the "yardland", an Old English unit of tax assessment, the term evolved to represent survey lengths of 15 or 16.5 feet, known as the "rod".

The origin of the yard is uncertain, with possible links to pacing, the ell or cubit, and King Henry I's arm standard. While some historians suggest it originated from the girth of a person's waist, others propose its roots as a cubic measure. Physical standards, including the Worshipful Company of Merchant Taylors' clothyard, played a role in establishing the yard's length.

In the 19th century, investigations led to defining the yard based on the length of a seconds pendulum, but this idea was not approved. The Weights and Measures Act of 1824 deterined the yard's length and subsequent legislation confirmed its status. However, it was not until 1959 that the international yard was officially defined as exactly 0.9144 metres.

In modern use, the yard persists in various contexts, including the measurement of field length in sport, road signs for shorter distances in the UK, and units of area and volume (square yard and cubic yard). It is also used in textiles, where fabric is often sold by the yard, and in the unique division of yards for measuring fabric.

The metre (m), the fundamental unit of length in the International System of Units (SI), originated in 1791 as one ten-millionth of the distance from the equator to the North Pole along a great circle, corresponding to the Earth's polar circumference of about 40,000 km. Over time, the definition has undergone changes, including reference to a prototype metre rod, wavelength measurements of krypton-86 and, from 1983 to 2019, the speed of light in a vacuum. The 2019 redefinition linked the metre to the caesium frequency.

Despite these changes, the size of the metre has remained constant: the Earth's polar circumference is now 40,007.863 km, a change of only 0.02% from the original 40,000 km. The word "meter" has linguistic roots in Greek and Latin words related to measurement, moderation and poetic meter. The use of "meter" in English dates back to at least 1797.

The development of the metre as a universal measure is closely linked to the figure of the earth and scientific advances. Beginning with the French Revolution and influenced by figures such as Copernicus, Galileo, Kepler and Huygens, the metre underwent various definitions based on the Earth's dimensions. Notable contributions include the determination of the metre by triangulation of the Paris meridian, advances in geodesy and the measurement of gravitational acceleration. The Metre Convention of 1875 established the International Bureau of Weights and Measures and standardised the metre as the distance between two lines on a platinum-iridium alloy bar. Worldwide adoption of the metric system and international cooperation further established the metre as the fundamental unit of length.

A fathom is a unit of length in the Imperial and U.S. Customary systems, equal to 6 feet, used primarily for measuring water depth. Although it is not an international standard unit, it has historically been important in marine depth measurement in the English-speaking world. The term "fathom" comes from an Old English word meaning "embracing arms". Its size, originally based on a man's outstretched arms, has varied throughout history. The international fathom is now exactly 1.8288 metres.

The British Admiralty defined a fathom as one thousandth of an imperial mile, or 6.08 feet (1.85 m). In practice, however, the "warship fathom" of exactly 6 feet (1.8 m) was used. Modern nautical charts now mainly use metres, although the U.S. Hydrographic Office still uses feet and fathoms. Historically, sounding lines marked in fathoms were used to measure depths in shallow water.

On land, a fathom has been used to measure the depth of mines, as a unit of area equal to 6 square feet in mining planes, and in British and Central European contexts to quantify timber piles or land areas. In addition, a minimum depth of six fathoms is usually required for burial at sea, giving rise to the expression "to deep six" for discarding or disposing of something. The historical significance of the fathom remains in various fields, although its practical use has diminished over time.

The chain, a unit of length equal to 66 feet (22 yards), is used in both the US Customary and Imperial unit systems. It consists of 100 links and has been used in England and other English-speaking countries for centuries. Ten chains make up a furlong and 80 chains make up a statute mile. In metric terms, one chain is equivalent to 20.1168 metres. Chainage refers to the distance along a survey line from a fixed starting point as measured by an odometer.

Originally, the Scottish and Irish customary miles had longer chains than the statute mile in the United Kingdom, with a Scottish chain being about 74 feet and an Irish chain being 84 feet. However, these variations became obsolete with the adoption of the imperial system in 1824.

In the United Kingdom, the chain is no longer used for practical surveying, but remains as a location marker on railways. In North America, the chain played an important role in the US Public Land Survey System, with federal law requiring its use in official government surveys. Chains and links are common in older metes and bounds legal descriptions, and the unit is still used in agriculture, wildfire measurement, and various historical references. In Australia and New Zealand the chain influenced land surveying, with street frontages often being one chain wide. In addition, the term "Queen's Chain" refers to a strip of public land along coastlines and waterways in New Zealand. The legacy of the chain extends to cricket pitches, where it represents the distance between the stumps.

The furlong, which originated in 17th century England, was originally a land surveying tool used to measure the distance a team of oxen could plough without resting (40 rods or 10 chains). The term "furlong" is derived from the Old English words "furh" (furrow) and "lang" (long), reflecting its origin in ploughed open fields.

In the imperial system, a furlong is one-eighth of a mile or 220 yards, around 201.168 metres in the metric system. In the U.S., some states use older definitions for surveying purposes, resulting in slight variations in length.

In Myanmar, furlongs are still used in motorway signs alongside miles. However, the primary modern use of the furlong is in horse racing in English-speaking countries, particularly the United Kingdom, Ireland, Canada and the United States. In these regions, races are often run in miles and furlongs.

The kilometre (km) is a unit of length in the International System of Units (SI), equal to one thousand metres. It is widely used throughout the world for measuring distances between geographical locations on land, with the exception of the United States and the United Kingdom, where the statute mile is the primary unit for expressing distance. The SI prefix "kilo-" denotes a factor of 1000.

Common abbreviations for the kilometre include "k" or "K", pronounced /keɪ/, although these are not recommended by the Bureau International des Poids et Mesures (BIPM). In military slang, the term "klick" is used in the United States, the United Kingdom and Canada.

The history of the kilometre dates back to the French Revolution, when in 1790 the French National Constituent Assembly asked the French Academy of Sciences to develop a new system of measurement. In 1799, the metre was established as the primary measure of length, based on 1/10 millionth of the distance from the Earth's poles to the equator. Initially, the term "myriametre" (10,000 metres) was preferred to 'kilometre' for everyday use, but the latter gained acceptance over time. The kilometre was officially recognised as a unit of length by the International Committee for Weights and Measures in 1935, with the prefix "myria-" and "myriametre" being abolished. The adoption of the kilometre varied across Europe, with the Netherlands adopting it in 1867 and other countries such as France and Italy using the myriametre in the mid-19th century.

The mile, derived from the Roman unit of one thousand paces, has evolved into various forms across different cultures. The British imperial and U.S. customary miles, both equivalent to 5,280 feet or 1,760 yards, were standardised in 1959 as exactly 1,609.344 metres. Beyond this standard, the term "mile" is used with qualifiers for various units, such as the nautical mile (1,852 km), the Italian mile and the Chinese mile. The modern English term "mile" has its roots in the Old English "mil", which can be traced back to the ellipsis of the Latin phrase "mille passus", meaning "a thousand steps".

The Roman mile, equal to 5,000 feet, influenced England in the Elizabethan era, leading to the establishment of the statute mile in 1593 as 8 furlongs or 5,280 feet. While many countries adopted the kilometre during the transition to the International System of Units (SI), the international mile persists in countries like the United Kingdom and the United States.

Historically, different cultures had their own miles, such as the Italian, Arabic, Welsh, Scottish and Irish miles, each with distinct lengths. The Dutch mile even had multiple definitions, including a small, medium, and large mile. Other examples include the German, Hungarian, Portuguese, Russian, Croatian and Ottoman miles. The international mile, agreed upon in 1959, is precisely 1.609344 kilometres and is currently used in several countries, especially those with historical ties to the UK or the U.S.

The nautical mile, a unit of length essential for air, sea and space navigation and for defining territorial waters, has evolved over time. Historically, it was based on the length of the meridian arc corresponding to one minute of latitude at the equator, resulting in the Earth's polar circumference being approximately 21,600 nautical miles. However, the now universally accepted international nautical mile is precisely defined as 1,852 metres, approximately 6,076 feet or 1.151 miles. This measurement is essential for determining distances at sea and is the basis for the derived unit of speed known as the knot, which is equivalent to one nautical mile per hour.

There is no universal agreement on the symbol for the nautical mile, with variations such as NM, nmi, M and nm used by different organisations. The concept of the nautical mile derives from the Latin phrase "mille passus", meaning a thousand paces, emphasising its historical association with Roman measurements. Over time, navigational tools and coordinate systems were developed, and the ratio of 60 miles to one degree became the standard. In the 17th century, geographers recognised the discrepancy between angular and linear measurements, leading to proposals to divide a degree into 100 parts. The modern definition of the nautical mile as 1,852 metres was established in 1929 and gained international acceptance and adoption in the subsequent years.

The league, once a common unit of length in Europe and Latin America, is no longer officially recognised in any nation. Derived from an ancient Celtic measure and adopted by the Romans as the leuga, the league served as a widespread unit of measurement in Western Europe, with various definitions emerging over time. It was roughly the distance a person could walk in an hour. In ancient Rome, it was equivalent to one and a half Roman miles. In England, it is most commonly defined as three miles on land (4.83 km) and three nautical miles at sea (5.556 km).

France had several variations of the league, ranging from 3.25 to 4.68 km. In Mexico, the league retains its original meaning of the distance one can walk in an hour. Portugal, Brazil and parts of the former Portuguese Empire had several types of leagues, both traditional and metric. Spain had several definitions, including the nautical league, the degree league, the geographical league and the maritime league. In Hispanic settlements in the Americas, a league was also a unit of area. Despite its historical significance, the league is now obsolete as an official unit of measurement.