metre

(m) measurement also spelled meter

Main

in measurement, fundamental unit of length in the metric system and in the International Systems of Units (SI). It is equal to approximately 39.37 inches in the British Imperial and United States Customary systems. The metre was historically defined by the French Academy of Sciences in 1791 as ¹/_10,000,000 of the quadrant of the Earth’s circumference running from the North Pole through Paris to the equator. The International Bureau of Weights and Measures in 1889 established the international prototype metre as the distance between two lines on a standard bar of 90 percent platinum and 10 percent iridium. By 1960 advances in the techniques of measuring light waves had made it possible to establish an accurate and easily reproducible standard independent of any physical artifact. In 1960 the metre was thus defined in the SI system as equal to 1,650,763.73 wavelengths of the orange-red line in the spectrum of the krypton-86 atom in a vacuum.

By the 1980s, advances in laser measurement techniques had yielded values for the speed of light in a vacuum of an unprecedented accuracy, and it was decided in 1983 by the General Conference on Weights and Measures that the accepted value for this constant would be exactly 299,792,458 metres per second. The metre is now thus defined as the distance traveled by light in a vacuum in ¹/_299,792,458 of a second.

Citations

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"metre." Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 19 Mar. 2009 <http://www.britannica.com/EBchecked/topic/378737/metre>.

APA Style:

metre. (2009). In Encyclopædia Britannica. Retrieved March 19, 2009, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/378737/metre

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Encyclopædia Britannica articles, from the full Encyclopædia Britannica database

metre

in poetry, the rhythmic pattern of a poetic line. Various principles, based on the natural rhythms of language, have been devised to organize poetic lines into rhythmic units. These have produced distinct kinds of versification, among which the most common are quantitative, syllabic, accentual, and accentual-syllabic.

metre

in measurement, fundamental unit of length in the metric system and in the International Systems of Units (SI). It is equal to approximately 39.37 inches in the British Imperial and United States Customary systems. The metre was historically defined by the French Academy of Sciences in 1791 as 110,000,000 of the quadrant of the Earth’s circumference running from the North Pole through Paris to the equator. The International Bureau of Weights and Measures in 1889 established the international prototype metre as the distance between two lines on a standard bar of 90 percent platinum and 10 percent iridium. By 1960 advances in the techniques of measuring light waves had made it possible to establish an accurate and easily reproducible standard independent of any physical artifact. In 1960 the metre was thus defined in the SI system as equal to 1,650,763.73 wavelengths of the orange-red line in the spectrum of the krypton-86 atom in a vacuum.

metre

in music, rhythmic pattern constituted by the grouping of basic temporal units, called beats, into regular measures, or bars; in Western notation, each measure is set off from those adjoining it by bar lines. A time (or metre) signature, found at the beginning of a piece of music, indicates the number of beats in a measure and the value of the basic beat. For example, 34 metre has three quarter-note beats per measure. The time signature implies that an accent regularly occurs on the first beat of each measure. Simple metres are duple (e.g., 22, 24), triple (34, 38), or quadruple (44, 48). Compound metres are also duple (68, 616), triple (98), or quadruple (128) but have time signatures that indicate the number of beats to be a multiple of three. Thus, in 68, for example, both beats of the basic duple division are divisible into three subunits, yielding a total of six. Some metres that occur less frequently are neither duple nor triple (54, 74) but may be considered a combination of duple and triple—such as 24+34 or 34+24+24.

gas meter

device for measuring the quantity or rate of flow of a gas. Types of gas meters (by operating principles) include displacement, velocity, head, thermal, acoustic, and tracer.

exposure meter

photographic auxiliary device that measures the intensity of light and indicates proper exposure (i.e., the combination of aperture and shutter speed) for film of a specific sensitivity. Modern instruments are of two basic types: the self-generating, or photovoltaic, and the variable resistance, or photoconductive.

Student Britannica Articles (Ages 11 and up) on "metre (measurement)" from the Britannica Online Student Edition

meter

An instrument that measures the flow of liquids, gases, or electricity is a meter. Meters may also be used to measure other physical data such as capacity, speed, or distance. Meters are found almost everywhere. In the home a gas meter measures the amount of natural gas consumed, an electric watt-hour meter records the amount of electricity used, and a water meter keeps track of water consumption. Flow meters are widely used in process industries to measure the flow rate of liquids, gases, or vapors. Fuel meters measure the fuel used by airplanes or power plants.

meter

Many of the water meters used in homes and apartment buildings are rotary disk meters. A rotating tilted disk in a chamber of known size separates the incoming water from the outlet section. In order for the water to pass through the meter, it has to rotate the disk. The number of rotationswhich is proportional to the water flowis registered on dials.

meter

To measure gas consumption in the home, a gas meter contains two bellows that are connected by valves to the main gas line. The bellows are alternately filled and emptied as the gas flows through the meter, and their action is used as a counting mechanism. Since the volume of gas enclosed in each bellows is known, this count provides a measure of the total gas flow rate, which is recorded on a series of dials. The difference between monthly dial readings is then used to determine the amount of the gas bill.

poetry

Apart from nonmetrical poetry, which is discussed below, most English-language verse relies on syllable-stress or strong-stress meters. Other languages, because of differences in word accentuation or verb and noun endings, use purely syllabic meters. This is true especially of French, Italian, and Spanish verse. In some French poetry the 12-syllable line is the dominant form. It must be noted that French words themselves have no accented syllables. The following line from a stanza by the 17th-century writer Jean Racine contains 12 syllables:O toi, qui vois la honte où je suis descendue,(O you, who see the shame into which I have descended)A comparable ten-syllable English line from a translation of the 14th-century Italian poet Petrarch reads as follows:The long love that in my thought doth harbor,In such poems only the count of syllables is fixed; the stresses are variable.

meter

Flow meters, sometimes call ratemeters, are the types of instruments most commonly associated with the word meter. They generally measure the flow of liquids, gases, or electricity.

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Children's Encyclopedia Articles (Ages 8-11) on "metre (measurement)" from the Britannica Online Student Edition

Physical features(from the Sault Sainte Marie canals article)

The Canadian canal is 1.4 miles (2.3 kilometers) long. An enclosure known as a lock raises or lowers ships to the water level of the lake they want to enter. The lock is 18.5 feet (5.6 meters) deep, 60 feet (18 meters) wide, and 850 feet (260 meters) long.

Combined Events(from the track and field article)

The decathlon and the heptathlon are tests of all-around athletes. They take two days to complete. In the Olympics, men compete in the decathlon and women in the heptathlon. The decathlon consists of ten events: the 100- and 400-meter dashes, the long jump, the shot put, the high jump, the 110-meter hurdles, the discus and javelin throws, the pole vault, and the 1,500-meter run. The heptathlon consists of seven events: the 100-meter hurdles, the high jump, the shot put, the 200-meter dash, the long jump, the javelin, and the 800-meter run. Points are awarded in each event. The points are added up to determine overall winners.

Playing area and equipment(from the rugby article)

Rugby is a game played by two teams. Rugby Union, or amateur rugby, is played with 15-member teams; Rugby League, or professional rugby, is played with 13-member teams. The game is played on a rectangular field, 69 meters wide. The length of the field, which is the distance between the goal lines, is 100 meters. The end zone area beyond the goal lines, called in goal, is 22 meters deep. The two goalposts, 5.6 meters apart, are at the center of the goal lines. They are connected with a crossbar 3 meters above the ground.

Michael Phelps(from the Phelps, Michael article)

Michael Phelps was a swimmer who brought worldwide attention to the sport. He gained particular attention when he won a record number of gold medals at the 2008 Olympic Games in Beijing, China.

Plants and Animals(from the Andes Mountains article)

Like the climate, the plant and animal life of the Andes varies with altitude. Some plants and animals can live at any height, and others can live only at certain levels. Lush tropical forests can be found at lower elevations of some parts of the Andes. At higher levels there is grassland. Above 13,000 feet (4,000 meters), only a few types of plants can resist the cold temperatures. Above 16,000 feet (4,877 meters), vegetation is almost absent.

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For a definition of "metre (measurement)", visit Merriam-Webster.

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metre

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More from Britannica on "metre (measurement)"...

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Children's Encyclopedia Articles (Ages 8-11) on "metre (measurement)" from the Britannica Online Student Edition

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