Metre

src: image.shutterstock.com

The meter (English spelling and BIPM spelling) or meter (American spelling) (from the French unit mÃÆ'¨tre , from the Greek noun? ?????, "size") is a long basic unit in several metric systems, including the International System of Units (SI). The SI unit symbol is m . The meter is defined as the length of the path through which light in a vacuum in the second 1 / 299 792 458 .

The meter was originally defined in 1793 as one ten million distance from the equator to the North Pole. In 1799, it was redefined in terms of a meter prototype bar (the actual bar used was changed in 1889). In 1960, the meter was redefined in terms of a certain number of wavelengths of a particular emission line of krypton-86. In 1983, the current definition was adopted.

Insertion imperial is defined as 0.0254 meters (2.54 centimeters or 25.4 millimeters). One meter of 3 ³ / ₈ inch is longer than one yard, which is about 39 Ã, ³ / ₈ inch.

Video Metre

Spelling

Meters are the standard spelling of metric units for length in almost all English-speaking countries except the United States and the Philippines, using meters. Other Germanic languages, such as German, Dutch, and Scandinavian also spell the word meters.

Measurements (such as ammeter, speedometer) are spelled "-meter" in all English variants. The "-meter" suffix has the same Greek origin as the unit of length.

Maps Metre

Etymology

The etymological roots meters can be traced to the Greek verb ?????? (metreo) (for measuring, computing or comparing) and the noun ?????? (metron) (size), used for physical measurements, for poetic meters and with extensions for moderation or avoiding extremism (such as "measured in your response"). These uses are also found in Latin ( metior , mensura ), French ( mÃÆ'¨tre , mesure ), English and other languages. The motto is ????? ??? (metro chro) on the seal of the International Bureau of Weight and Size (BIPM), which is the word of Greek statesman and philosopher Pittacus of Mytilene and can be translated as "Use size!", calls for measurement and moderation.

src: cdn.shopify.com

Definition history

In 1668, British scholar and philosopher John Wilkins proposed in a long unit essay based on decimal, universal or standardized beneath the pendulum with a period of two seconds. The use of pendulum seconds to determine the length has been suggested to the Royal Society in 1660 by Christopher Wren. Christiaan Huygens has observed that its length becomes 38 inch Rijnland or 39.26 inches UK; ie, 997 Ã, mm. No official action was taken regarding this suggestion.

In 1670 Gabriel Mouton, the bishop of Lyon, also suggested a universal length standard with multiples and decimal divisions, based on the one-minute angle of the Earth's meridian arc or (because the Earth's circumference is not easily measured) on a pendulum with a two-second period. In 1675, the Italian scientist Tito Livio Burattini, in his Misura Universale , uses the phrase metro cattolico (" universal size "), derived from the Greek ??? ??? ????????? ( mÃÆ' Â © tron ​​â € <â € ), to denote the standard unit of length originating from the pendulum. As a result of the French Revolution, the French Academy of Sciences commissioned a commission by setting a single scale for all actions. On 7 October 1790 the commission suggested the adoption of the decimal system, and on 19 March 1791 suggested the adoption of the term "mÃÆ'¨tre (" size "), the long base unit, which they defined as one ten million spacing between the Poles North and the Equator. In 1793, the French National Convention adopted the proposal; the use of meters in English starts at least since 1797.

Definition of Meridional

In 1791, the French Academy of Sciences chose a meridional definition of a pendular definition because the force of gravity varied slightly above the Earth's surface, affecting the pendulum period.

To build a universally accepted ground for meter definitions, more accurate measurements of these meridians are required. The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre MÃÆ' Â © chain, lasting 1792-1799, which sought to accurately measure the distance between the bell tower towers at Dunkerque and MontjuÃÆ'¯c castle in Barcelona to estimate the length of the meridian arc via Dunkerque. Part of this meridian, which is considered as long as the Parisian longitude, is the basis for the half-meridian length that connects the Arctic to the Equator. The problem with this approach is that the exact shape of the Earth is not a simple mathematical form, such as spheroidal ball or oblate, at the level of precision required to define a standard length. The irregular and special shape of the earth that is polished to the surface of the ocean is represented by a mathematical model called geoid, which literally means "Earth-shaped". Apart from this problem, in 1793 France adopted the meter definition as the official long unit based on the interim results of this expedition. However, it was then determined that the first prototype meter rod was short about 200 micrometers due to miscalculation of Earth's alignment, making the prototype about 0.02% shorter than the original proposed definition of meter. Regardless, this length became the French standard and was increasingly adopted by other countries in Europe.

The expedition was focussed on Denis Guedj, Le mÃÆ'¨tre du Monde . Ken Alder writes factually about the expedition on The Size of All Things: seven years of wandering and hidden mistakes that changed the world .

International prototype meter bar

In 1867 at the second general conference of the International Geodesy Association held in Berlin, the question of a long unit of international standards has been discussed to combine measurements made in various countries to determine the size and shape of the Earth. The conference recommended the adoption of meter and manufacture of international meter commissions, in accordance with the proposals of Johann Jacob Baeyer, Adolphe Hirsch and Carlos IbÃÆ'¡ÃÆ' Â ± ez e IbÃÆ'¡ÃÆ' Â ± ez de Ibero.

In the 1870s and in the light of modern accuracy, a series of international conferences were held to design new metric standards. The Convention Convention on Convention of 1873 mandated the establishment of the International Bureau of Weights and Measures (BIPM: Bureau of the International Bureau of Convention ( Convention du MÃÆ'¨ rere ) des Poids et Mesures ) is located in SÃÆ'¨vres, France. This new organization is to build and preserve prototype meter bars, distribute prototypes of national metrics, and maintain a comparison between them and non-metric measurement standards. This organization made such a bar in 1889 at the first General Conference on Weight and Size (CGPM: ConfÃÆ' Â © rence GÃÆ' Â © nÃÆ' Â © rale des Poids et Mesures ), sets the International Prototype Meter as the distance between two lines on a standard bar consisting of a 90% platinum alloy and 10% iridium, measured at the melting point of ice.

The original international prototype meter was still stored at BIPM under the conditions specified in 1889.

Definition of wavelength

In 1893, the standard meter was first measured by interferometer by Albert A. Michelson, the inventor of the device and advocates the use of certain wavelengths of light as a standard length. In 1925, interferometry was used regularly at BIPM. However, the International Prototype Meter remained standard until 1960, when the eleventh CGPM defined the meter in the new International Unit System (SI) equal to 1 650 763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton. -86 atoms in a vacuum.

Speed ​​Definition Light

To further reduce the uncertainty, the 17th CGPM in 1983 replaced the definition of meters with the current definition, thus improving the meter length in terms of both and the speed of light:

The meter is the length of the path through which light in a vacuum over the second time interval 1/ 299 792 458 second.

This definition improves the speed of light in a vacuum exactly 299 792 458 meters per second (? 300 000 km/s ). The by-product of the 17th CGPM definition is that it allows scientists to accurately compare lasers using frequencies, generating wavelengths with a fifth of the uncertainties involved in the direct ratio of wavelengths, since interferometer errors are eliminated. To further facilitate reproducibility from the laboratory to the laboratory, the 17th CGPM also makes the iodine-stabilized helium-neon laser "suggested radiation" to realize the meter. For metric meter purposes, BIPM is currently considering the HeNe laser wavelength, ? _HeNe , being 632.991 212 58 Ã,nm with an estimate of relative standard uncertainty ( U ) from 2.1 ÃÆ' - 10 ^-11 . This uncertainty is currently one of the limiting factors in the laboratory realization of meters, and it is a few orders of magnitude less than the second, based on the atomic clock of cesium fountain ( = 5 ÃÆ' - 10 ^-16 ). As a result, meter realizations are usually depicted (not defined) today in the lab as 1 579 800 .762 042 (33) wavelength of helium-neon laser light in a vacuum, the error states only that the determination of the frequency. This bracket notation states an error is described in the article about measurement uncertainty.

The practical realities of this meter are subject to uncertainties in media characterization, uncertainty of interferometry, and uncertainty in measuring source frequencies. The commonly used medium is air, and the National Institute of Standards and Technology (NIST) has set up an online calculator to convert wavelengths in a vacuum to wavelengths in the air. As explained by NIST, in the air, the uncertainty in characterizing the medium is dominated by errors in measuring temperature and pressure. The error in the theoretical formula used is secondary. By applying such a refractive index correction, an approximate meter estimate may be implemented in the air, for example, using a meter formulation as 1 579 800 .762 042 (33) the wavelength of the helium-neon laser beam in a vacuum, and change the wavelength in a vacuum to the wavelength in the air. Air is only one of the possible mediums for use in meter realization, and any partial vacuum can be used, or some inert atmosphere such as helium gas, provided the correct correction for refractive index is applied.

The meter is defined as the length of the path traversed by the light in a given time and the measurement of the practical laboratory length in meters is determined by calculating the number of wavelengths of a laser beam of one of the standard types corresponding to the length, and changing the unit of wavelength selected to be meter. Three main factors limit the accuracy achieved with the laser interferometer for measurement of length:

• the uncertainty in the vacuum wavelength from the source,
• uncertainty in medium refractive index,
• minimum interferometer count resolution.

Dari jumlah ini, yang terakhir adalah aneh untuk interferometer itu sendiri. Konversi panjang gelombang menjadi panjang dalam meter didasarkan pada relasinya

${\ displaystyle \ lambda = {\ frac {c} {nf}},}  ÂÂ$

which changes the unit of wavelength? to meters using c , the speed of light in a vacuum in m/s. Here n is the refractive index of the medium where the measurement is performed, and f is the measured frequency of the source. Although the conversion from wavelength to meter introduces additional errors in overall length due to measurement error in determining refractive index and frequency, frequency measurement is one of the most accurate measurements available.

Timeline

• May 8, 1790 - The French National Assembly decides that the new meter length will be the same as the length of the pendulum with half a period of one second.
• March 30, 1791 - The French National Assembly accepts a proposal from the French Academy of Sciences that the new definition for this meter equals one ten million quadrant lengths along the Earth's meridian through Paris, it is the distance from the equator to the north pole along that quadrant.
• 1795 - Temporary meter bar made of brass. Based on Bessel's ellipsoid and legally equivalent to 443.44 line on toise du PÃÆ' Â © rou (the standard long French unit of 1747).
• December 10, 1799 - The French National Assembly establishes a platinum meter rod, which was built on June 23, 1799 and deposited in the National Archives, as the final standard. Legally equal to 443,296 lines on toise du PÃÆ' Â © rou .
• September 28, 1889 - First General Conference on Weight and Size (CGPM) defines the meter as the distance between two lines on a standard bar of platinum alloy with 10% iridium, measured at the melting point of ice./li>
• October 6, 1927 - The 7th CGPM redefines the meter as distance, at 0 Ã, Â ° C (273Ã, K), between the axes of the two center lines marked on the platinum-iridium prototype bar, this bar is subject to one standard pressure atmosphere and supported on two cylinders with a diameter of at least 10 mm (1 cm), symmetrically placed on the same horizontal plane at a distance of 571 mm (57.1 cm) to each other.
• October 14, 1960 - The 11th CGPM defines the meter as 1 650 763 .73 wavelength in a vacuum of radiation corresponding to transition between 2p ¹⁰ and 5d ⁵ quantum level of krypton-86 atom.
• October 21, 1983 - The 17th CGPM defines the meter as the path length that light passes through in a vacuum over the time interval / 299 792 458 2002 - The International Committee on Weights and Measures (CIPM) regards the meter as the exact unit length and thus recommends this definition is limited to "a short enough length l for the effect predicted by general relativity negligible with respect to the uncertainty of realization".

src: c8.alamy.com

SI prefix form meter

SI prefixes are often used to denote decimal multiples and submultiples of meters, as shown in the table below. As shown in the table, some are commonly used, while others do not. Distance is usually expressed in miles, astronomical units (149.6 Gm), light years (10 Pm), or parsec (31 Pm), rather than Mm, Gm, Tm, Pm, Em, Zm or Ym; "30 cm", "30 m", and "300 m" are more common than "3 dm", "3 dams", and "3 hm" respectively.

The term micron and (sometimes) millimeters are often used instead of micrometers (? M) and nanometers ), but this practice is officially restricted.

src: c8.alamy.com

Setara dalam unit lain

In this table, "inches" and "pages" mean "international inches" and "international pages" respectively, although the estimated conversion in the left column applies to both international and survey units.

"?" means "approximately equal to";

"?" means "the same as the definition" or "exactly the same as".

One meter is exactly as 10 000 / 254 Ã, inches and to < span> 10 000 / 9 144 Ã, yards.

Simple mnemonic help is there to help with conversions, like three "3":

1 meter is almost equivalent to 3 feet 3 ³ / ₈ Ã, inches. This gives an overestimate of 0.125 Ã, mm. However, the practice of memorizing such conversion formulas has been discouraged in favor of the practice and visualization of metric units.

Source of the article : Wikipedia