The metre (meter in the US), symbol m, is the base unit of length in the International System of Units (SI). Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole (at sea level), its definition has been periodically refined to reflect growing knowledge of metrology. Since 1983, it has been defined as "the length of the path travelled by light in vacuum during a time interval of 1 ⁄ 299,792,458 of a second".^[1]

History[link]

Name[link]

The first recorded proposal for a decimal-based unit of length was the universal measure unit proposed by the English philosopher John Wilkins in 1668.^[2] In 1675, the Italian scientist Tito Livio Burattini, in his work Misura Universale, used the words metro cattolico (lit. "catholic [i.e. universal] metre"), which was derived from the Greek μέτρον καθολικόν (métron katholikón), "a universal measure". This word gave rise to the French mètre which in 1797 was introduced into the English language.^[3]

Belfry, Dunkirk - the northern end of the meridian arc

Fortress of Montjuïc - the southerly end of the meridian arc

Meridional definition[link]

In 1668, Wilkins proposed using Christopher Wren's suggestion of a pendulum with a half-period of one second to measure a standard length that Christiaan Huygens had observed to be 38 Rhineland or 39¼ English inches (997 mm) in length.^[2] In the 18th century, there were two favoured approaches to the definition of the standard unit of length. One approach followed Wilkins in defining the metre as the length of a pendulum with a half-period of one second, a 'seconds pendulum'. The other approach suggested defining the metre as one ten-millionth of the length of the Earth's meridian along a quadrant, that is the distance from the equator to the North Pole. In 1791, the French Academy of Sciences selected the meridional definition over the pendular definition because the force of gravity varies slightly over the surface of the Earth, which affects the period of a pendulum.

To establish a universally accepted foundation for the definition of the metre, measurements of this meridian more accurate than those available at that time were imperative. The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain, lasting from 1792 to 1799, which measured the distance between the Dunkerque belfry and Montjuïc castle, Barcelona to estimate the length of the meridian arc through Dunkerque (assumed to be the same length as the Paris meridian). This portion of the meridian was to serve as the basis for the length of the half meridian, connecting the North Pole with the equator. The exact shape of the Earth is not a simple mathematical shape (sphere or oblate spheroid) at the level of precision required for defining a standard of length. The irregular and particular shape of the Earth (smoothed to sea level) is called a Geoid, which means "Earth-shaped".

However, in 1793, France adopted as its official unit of length a metre based on provisional results from the expedition. Although it was later determined that the first prototype metre bar was short by a fifth of a millimetre because of miscalculation of the flattening of the Earth, this length became the standard. The circumference of the Earth through the poles is therefore slightly more than forty million metres (40 007 863).^[4]

Prototype metre bar[link]

Creating the metre-alloy in 1874 at the Conservatoire des Arts et Métiers. Present Henri Tresca, George Matthey, Saint-Claire Deville and Debray

Historical International Prototype Metre bar, made of an alloy of platinum and iridium, that was the standard from 1889 to 1960.

In the 1870s and in light of modern precision, a series of international conferences was held to devise new metric standards. The Metre Convention (Convention du Mètre) of 1875 mandated the establishment of a permanent International Bureau of Weights and Measures (BIPM: Bureau International des Poids et Mesures) to be located in Sèvres, France. This new organisation would preserve the new prototype metre and kilogram standards when constructed, distribute national metric prototypes, and maintain comparisons between them and non-metric measurement standards. The organisation created a new prototype bar in 1889 at the first General Conference on Weights and Measures (CGPM: Conférence Générale des Poids et Mesures), establishing the International Prototype Metre as the distance between two lines on a standard bar composed of an alloy of ninety percent platinum and ten percent iridium, measured at the melting point of ice.^[5]

The original international prototype of the metre is still kept at the BIPM under the conditions specified in 1889. A discussion of measurements of a standard metre bar and the errors encountered in making the measurements is found in a NIST document.^[6]

Standard wavelength of krypton-86 emission[link]

In 1893, the standard metre was first measured with an interferometer by Albert A. Michelson, the inventor of the device and an advocate of using some particular wavelength of light as a standard of length. By 1925, interferometry was in regular use at the BIPM. However, the International Prototype Metre remained the standard until 1960, when the eleventh CGPM defined the metre in the new SI system as equal to 1,650,763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum.^[7]

Speed of light[link]

To further reduce uncertainty, the seventeenth CGPM in 1983 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light:

The metre is the length of the path travelled by light in vacuum during a time interval of 1  ⁄   299,792,458 of a second.^[1]

This definition fixed the speed of light in vacuum at exactly 299,792,458 metres per second. An intended by-product of the 17th CGPM’s definition was that it enabled scientists to compare their lasers accurately using frequency, resulting in wavelengths with one-fifth the uncertainty involved in the direct comparison of wavelengths because interferometer errors were eliminated. To further facilitate reproducibility from lab to lab, the 17th CGPM also made the iodine-stabilised helium–neon laser “a recommended radiation” for realising the metre.^[8] For purposes of delineating the metre, the BIPM currently considers the HeNe laser wavelength to be as follows: λ_HeNe = 632 991 212.58 fm with an estimated relative standard uncertainty (U ) of 2.1×10⁻¹¹.^[9][10] This uncertainty is currently one limiting factor in laboratory realisations of the metre, and it is several orders of magnitude poorer than that of the second, based upon the caesium fountain atomic clock (U = 5×10⁻¹⁶ ).^[11] Consequently, a realisation of the metre is usually delineated (not defined) today in labs as 1,579,800.762042(33) wavelengths of helium-neon laser light in vacuum, the error stated being only that of frequency determination.^[12] This bracket notation expressing the error is explained in the article on measurement uncertainty.

Practical realisation of the metre is subject to uncertainties in characterising the medium, in addition to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source.^[13] A commonly used medium is air, and NIST has set up an on-line calculator to convert wavelengths in vacuum to wavelengths in air.^[14] As described by NIST, in air the uncertainties in characterising the medium are dominated by errors in finding temperature and pressure, and errors in the theoretical formulas used are secondary.^[15] By implementing a refractive index correction such as this, an approximate realization of the metre can be implemented in air, for example, using the formulation of the metre as 1,579,800.762042(33) wavelengths of helium-neon laser light in vacuum, and converting the wavelengths in vacuum to wavelengths in air. Of course, air is only one possible medium to use in a realization of the metre, and any partial vacuum can be used, or some inert atmosphere like helium gas, provided the appropriate corrections for refractive index are implemented.^[16]

Length measurement in metres[link]

Although the metre is now defined as the path length travelled by light in a given time, actual laboratory length measurements in metres are determined by counting the number of wavelengths of laser light of one of the standard types that fit into the length,^[8][17] and converting the selected unit of wavelength to metres. Three major factors limit the accuracy attainable with laser interferometers for a length measurement:^[18][13]

• Uncertainty in vacuum wavelength of the source,
• Uncertainty in the refractive index of the medium,
• Least count resolution of the interferometer.

Of these, the last is peculiar to the interferometer itself. The conversion of a length in wavelengths to a length in metres is based upon the relation:

Failed to parse (Missing texvc executable; please see math/README to configure.): \lambda = \frac{c}{n f} \

which converts the unit of wavelength λ to metres using c, the speed of light in vacuum in m/s. Here n is the refractive index of the medium in which the measurement is made; and f is taken for the conversion here as the measured frequency of the source. Although conversion from wavelengths to metres introduces additional error in the overall length due to measurement error in determining the refractive index and the frequency, measurement of frequency is one of the most accurate measurements available.^[18]

Timeline of definition[link]

• 1790 May 8 – The French National Assembly decides that the length of the new metre would be equal to the length of a pendulum with a half-period of one second.
• 1791 March 30 – The French National Assembly accepts the proposal by the French Academy of Sciences that the new definition for the metre be equal to one ten-millionth of the length of the Earth's meridian along a quadrant through Paris, that is the distance from the equator to the north pole.
• 1795 – Provisional metre bar constructed of brass.
• 1799 December 10 – The French National Assembly specifies the platinum metre bar, constructed on 23 June 1799 and deposited in the National Archives, as the final standard.
• 1889 September 28 – The first General Conference on Weights and Measures (CGPM) defines the metre as the distance between two lines on a standard bar of an alloy of platinum with ten percent iridium, measured at the melting point of ice.
• 1927 October 6 – The seventh CGPM adjusts the definition of the metre to be the distance, at 0 °C, between the axes of the two central lines marked on the prototype bar of platinum-iridium, this bar being subject to one standard atmosphere of pressure and supported on two cylinders of at least one centimetre diameter, symmetrically placed in the same horizontal plane at a distance of 571 millimetres from each other.
• 1960 October 14 – The 11th CGPM defines the metre to be equal to 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the transition between the 2p¹⁰ and 5d⁵ quantum levels of the krypton-86 atom.^[19]
• 1983 October 21 – The 17th CGPM defines the metre as equal to the length of the path travelled by light in vacuum during a time interval of ¹⁄_299,792,458 of a second.^[20]
• 2002  – The International Committee for Weights and Measures (CIPM) considers the metre to be a unit of proper length and thus recommends this definition be restricted to "lengths ℓ which are sufficiently short for the effects predicted by general relativity to be negligible with respect to the uncertainties of realisation".^[21]

SI prefixed forms of metre[link]

SI prefixes are often employed to denote decimal multiples and submultiples of the metre, as shown in the table below. As indicated in the table, some are commonly used, while others are not. Long distances are usually expressed in km, astronomical units (149.6 Gm), light-years (10 Pm), or parsecs (31 Pm), rather than in Mm, Gm, Tm, Pm, Em, Zm or Ym; "30 cm", "30 m", and "300 m" are more common than "3 dm", "3 dam", and "3 hm", respectively.

The term micron is often used instead of micrometre, but this practice is officially discouraged.^[23]

Spelling[link]

Metre is used as the standard spelling of the metric unit for length in all English-speaking nations except the USA, which uses meter.^[24]

The most recent official brochure, written in 2006, about the International System of Units (SI), Bureau international des poids et mesures, was written in French by the International Bureau of Weights and Measures. An English translation (using the spelling: metre) is included to make the SI standard "more widely accessible".^[25]

In 2008, the U.S. English translation published by the U.S. National Institute of Standards and Technology chose to use meter in accordance with the United States Government Printing Office Style Manual.^[26]

Measuring devices (such as parking meter, speedometer) are traditionally spelt "...meter" in all countries.^[27] The word "meter", signifying any such device, has the same derivation as the word "metre", denoting the unit of length this article is about.^[28]

Equivalents in other units[link]

Within this table, "inch" (and "yard") means "international inch" (and yard).^[29] though approximate conversions in the left-hand column hold for both international units and survey units.

"≈" means "is approximately equal to".

"≡" means "equals by definition" or equivalently, "is exactly equal to".

One metre is exactly equivalent to ¹⁰⁰⁰⁰⁄₂₅₄ inches and to ¹⁰⁰⁰⁰⁄₉₁₄₄ yards.

A simple mnemonic aid exists to assist with conversion, as three "3":

1 metre is nearly equivalent to 3 feet, 3 and 3/8 inches.^[30] This gives an over-estimate of 0.125 mm.

The ancient Egyptian cubit was about ½ m (surviving rods are 52.3–52.9 cm). Scottish and English definitions of ell (two cubits) were 0.941 m and 1.143 m, respectively. The ancient Paris toise (fathom) was slightly shorter than 2 m, and was standardized at exactly 2 m in the mesures usuelles system, such that 1 m was exactly ½ toise. The Russian verst was 1.0668 km. The Swedish mil was 10.688 km, but was changed to 10 km when Sweden converted to metric units.

See also[link]

• Conversion of units for comparisons with other units
• International System of Units
• ISO 1 – standard reference temperature for length measurements
• Length measurement
• Metre Convention
• Metric system
• Introduction to the metric system
• Metrication
• Orders of magnitude (length)
• SI prefix
• Speed of light

Notes[link]

References[link]

• 17th General Conference on Weights and Measures. (1983). Resolution 1. International Bureau of Weights and Measures.
• American Heritage Dictionary of the English Language. 3rd ed. (1992). Boston: Houghton Mifflin.
• Astin, A. V. & Karo, H. Arnold, (1959), Refinement of values for the yard and the pound, Washington DC: National Bureau of Standards, republished on National Geodetic Survey web site and the Federal Register (Doc. 59-5442, Filed, 30 June 1959, 8:45 a.m.)
• Barbrow, Louis E. & Judson, Lewis V. (1976). Weights and Measures of the United States: A brief history (Special Publication 447).. National Institute of Standards and Technology.
• Beers, J.S. & Penzes, W. B. (1992). NIST Length Scale Interferometer Measurement Assurance. (NISTIR 4998). National Institute of Standards and Technology.
• Bureau International des Poids et Mesures. (2006). The International System of Units (SI). Retrieved 18 August 2008.
  • HTML version. Retrieved 24 August 2008.
• Bureau International des Poids et Mesures. (n.d.). Resolutions of the CGPM (search facility). Retrieved 3 June 2006.
• Bureau International des Poids et Mesures. (n.d.). The BIPM and the evolution of the definition of the metre. Retrieved 3 June 2006.
• Cambridge Advanced Learner's Dictionary (2008). Cambridge University Press.
• Cardarelli, Francois (2003). Encydopaedia of scientific units, weights, and measures: their SI equivalences and origins, Springer-Verlag London Limited, ISBN 1-85233-682-X, page 5, table 2.1, data from Giacomo, P., Du platine a la lumiere, Bull. Bur. Nat. Metrologie, 102 (1995) 5–14.
• Humerfelt, Sigurd. (26 October 2010). How WGS 84 defines Earth. Retrieved 29 April 2011.
• Layer, H.P. (2008). Length—Evolution from Measurement Standard to a Fundamental Constant. Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 18 August 2008.
• Merriam-Webster Online Dictionary. Retrieved 8 December 2009.
• Mohr, P., Taylor, B.N., and David B. Newell, D. (28 December 2007). CODATA Recommended Values of the Fundamental Physical Constants: 2006. Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 18 August 2008.
• National Institute of Standards and Technology. (December 2003). The NIST Reference on Constants, Units, and Uncertainty: International System of Units (SI) (web site):
  • SI base units. Retrieved 18 August 2008.
  • Definitions of the SI base units. Retrieved 18 August 2008.
  • Historical context of the SI: Metre. Retrieved 26 May 2010.
• National Institute of Standards and Technology. (27 June 2011). NIST-F1 Cesium Fountain Atomic Clock. Author.
• National Physical Laboratory. (25 March 2010). Iodine-Stabilised Lasers. Author.
• National Research Council Canada. (5 February 2010). Maintaining the SI unit of length. Retrieved 4 December 2010.
• Naughtin, Pat. (2008). Spelling metre or meter. Author.
• Penzes, W. (29 December 2005). Time Line for the Definition of the Meter. Gaithersburg, MD: National Institute of Standards and Technology — Precision Engineering Division. Retrieved 4 December 2010.
• Taylor, B.N. and Thompson, A. (Eds.). (2008a). The International System of Units (SI). United States version of the English text of the eighth edition (2006) of the International Bureau of Weights and Measures publication Le Système International d’ Unités (SI) (Special Publication 330). Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 18 August 2008.
• Taylor, B.N. and Thompson, A. (2008b). Guide for the Use of the International System of Units (Special Publication 811). Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 23 August 2008.
• Tibo Qorl. (2005) The History of the Meter (Translated by Sibille Rouzaud). Retrieved 18 August 2008.
• Turner, J. (Deputy Director of the National Institute of Standards and Technology). (16 May 2008)."Interpretation of the International System of Units (the Metric System of Measurement) for the United States". Federal Register Vol. 73, No. 96, p. 28432-3.
• Wilkins, J. (c. 2007). An essay towards a real character, and a philosophical language.[Also available without images of original.] Metrication Matters. (Reprinted from title page and pp. 190–194 of original, 1668, London: Royal Society)
• Zagar, B.G. (1999). Laser interferometer displacement sensors in J.G. Webster (ed.). The Measurement, Instrumentation, and Sensors Handbook. CRC Press. isbn=0-8493-8347-1.
• "(Mise en Pratique) MEP 2003: Iodine (λ≈633nm)". BIPM. 2003. http://www.bipm.org/utils/common/pdf/mep/M-e-P_I2_633.pdf. 

Further reading[link]

• Alder, Ken. (2002). The Measure of All Things : The Seven-Year Odyssey and Hidden Error That Transformed the World. Free Press, New York ISBN 0-7432-1675-X

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Usain Bolt

Bolt at Berlin World Championships 2009
Personal information
Nickname(s)	Lightning Bolt
Nationality	Jamaican
Born	(1986-08-21) 21 August 1986 (age 25)[1] Trelawny, Jamaica[2]
Residence	Kingston, Jamaica
Height	1.95 m (6 ft 5 in)[3]
Weight	92 kg (200 lb)[3]
Sport
Sport	Track and field
Event(s)	Sprints
Club	Racers Track Club
Achievements and titles
Personal best(s)	100 m: 9.58 WR (Berlin 2009)[4] 150 m: 14.35 WB[5] (Manchester 2009)[6] 200 m: 19.19 WR (Berlin 2009)[7] 400 m: 45.28 (Kingston 2007)[1]
Medal record Men's athletics Competitor for  Jamaica Olympic Games Gold 2008 Beijing 100 m Gold 2008 Beijing 200 m Gold 2008 Beijing 4×100 m relay World Championships Gold 2011 Daegu 200 m Gold 2011 Daegu 4×100 m relay Gold 2009 Berlin 100 m Gold 2009 Berlin 200 m Gold 2009 Berlin 4×100 m relay Silver 2007 Osaka 200 m Silver 2007 Osaka 4×100 m relay World Athletics Final Gold 2009 Thessaloniki 200 m CAC Championships Gold 2005 Nassau 200 m World Junior Championships Gold 2002 Kingston Silver 2002 Kingston 4×100 m relay Silver 2002 Kingston 4×400 m relay Pan American Junior Championships Gold 2003 Bridgetown 200 m Silver 2003 Bridgetown 4×100 m relay CARIFTA Games (Junior) Gold 2004 Hamilton 200 m Gold 2004 Hamilton 4×100 m relay Gold 2004 Hamilton 4×400 m relay Gold 2003 Port of Spain 200 m Gold 2003 Port of Spain 400 m Gold 2003 Port of Spain 4×100 m relay Gold 2003 Port of Spain 4×400 m relay World Youth Championships Gold 2003 Sherbrooke 200 m CAC Junior Championships (Youth) Gold 2002 Bridgetown 200 m Gold 2002 Bridgetown 400 m Gold 2002 Bridgetown 4×100 m relay Gold 2002 Bridgetown 4×400 m relay CARIFTA Games (Youth) Gold 2002 Nassau 200 m Gold 2002 Nassau 400 m Gold 2002 Nassau 4×400 m relay Silver 2001 Bridgetown 200m Silver 2001 Bridgetown 400m Competitor for the Americas World Cup Silver 2006 Athens 200 m

The Honourable Usain St. Leo Bolt, OJ, C.D. ( /ˈjuːseɪn/;^[8] born 21 August 1986), is a Jamaican sprinter and a five-time World and three-time Olympic gold medalist. He is the world record and Olympic record holder in the 100 metres, the 200 metres and (along with his teammates) the 4×100 metres relay. He is the reigning Olympic champion in these three events, and is one of only seven athletes (along with Valerie Adams, Veronica Campbell-Brown, Jacques Freitag, Yelena Isinbayeva, Jana Pittman, Dani Samuels) to win world championships at the youth, junior, and senior level of an athletic event.

Bolt won a 200 m gold medal at the 2002 World Junior Championships, making him the competition's youngest-ever gold medalist at the time (since surpassed by Jacko Gill). In 2004, at the CARIFTA Games, he became the first junior sprinter to run the 200 m in less than 20 seconds with a time of 19.93 s,^[9] breaking the previous world junior record held by Roy Martin by two-tenths of a second. He turned professional in 2004, and although he competed at the 2004 Summer Olympics, he missed most of the next two seasons due to injuries. In 2007, he broke Don Quarrie's 200 m Jamaican record with a run of 19.75 s.

His 2008 season began with his first world record performance—a 100 m world record of 9.72 s—and culminated in world and Olympic records in both the 100 m and 200 m events at the 2008 Beijing Summer Olympics. He ran 9.69 s for the 100 m and 19.30 s in the 200 m, and also set a 4×100 m relay record of 37.10 s with the Jamaican team. This made him the first man to win three sprinting events at a single Olympics since Carl Lewis in 1984, and the first man to set world records in all three at a single Olympics. The following year he further lowered his own 100 m and 200 m world records to 9.58 s and 19.19 s respectively at the 2009 World Championships.^[10] This made him the first man to hold both the 100 and 200 m world and Olympic titles at the same time.

His 2009 record breaking margin over 100 m is the highest since the start of digital time measurements.^[11] His achievements in sprinting have earned him the media nickname "Lightning Bolt",^[12] and awards including the IAAF World Athlete of the Year, Track & Field Athlete of the Year, and Laureus Sportsman of the Year.

Early years[link]

Bolt was born on 21 August 1986 in Sherwood Content,^[13] a small town in Trelawny, Jamaica, and grew up with his parents, Wellesley and Jennifer Bolt, his brother Sadeeki,^[14] and his sister Sherine.^[2][15] His parents ran the local grocery store in the rural area, and Bolt spent his time playing cricket and football in the street with his brother,^[16] later saying, "When I was young, I didn’t really think about anything other than sports".^[17]

As a child, he attended Waldensia Primary and All-age School, and it was here that he first began to show his sprinting potential, running in the annual national primary-schools' meeting for his parish.^[12] By the age of twelve, Bolt had become the school's fastest runner over the 100 metres distance.^[18]

Upon his entry to William Knibb Memorial High School, Bolt continued to focus on other sports, but his cricket coach noticed Bolt's speed on the pitch and urged him to try track and field events.^[19] Pablo McNeil, a former Olympic sprint athlete,^[20] and Dwayne Barrett coached Bolt, encouraging him to focus his energy on improving his athletic abilities. The school had a history of success in athletics with past students, including sprinter Michael Green.^[12] Bolt won his first annual high school championships medal in 2001, taking the silver medal in the 200 metres with a time of 22.04 seconds.^[12] McNeil soon became his primary coach, and the two enjoyed a positive partnership, although McNeil was occasionally frustrated by Bolt's lack of dedication to his training and his predisposition to practical jokes.^[20]

Early competitions[link]

Performing for Jamaica in his first Caribbean regional event, Bolt clocked a personal best of 48.28 s in the 400 metres in the 2001 CARIFTA Games, winning a silver medal. The 200 m also yielded a silver as Bolt finished in 21.81 s.^[21]

He made his first appearance on the world stage at the 2001 IAAF World Youth Championships in Debrecen, Hungary. Running in the 200 m event, he failed to qualify for the finals, but he still set a new personal best of 21.73 s.^[22] Bolt still did not take athletics or himself too seriously, however, and he took his mischievousness to new heights by hiding in the back of a van when he was supposed to be preparing for the 200 m finals at the CARIFTA Trials. He was detained by the police for his practical joke, and there was an outcry from the local community, which blamed coach McNeil for the incident.^[20] However, the controversy subsided, and both McNeil and Bolt went to the CARIFTA Games, where Bolt set championship records in the 200 m and 400 m with times of 21.12 s and 47.33 s, respectively.^[21] He continued to set records with 20.61 s and 47.12 s finishes at the Central American and Caribbean Junior Championships.^[23]

Former Prime Minister P. J. Patterson recognised Bolt's talent and arranged for him to move to Kingston, along with Jermaine Gonzales, so he could train with the Jamaica Amateur Athletic Association (JAAA) at the University of Technology, Jamaica.^[20]

Rise to prominence[link]

The 2002 World Junior Championships before a home crowd in Kingston, Jamaica, gave Bolt a chance to prove his credentials on the world stage. By the age of 15, he had grown to 1.96 metres (6 ft 5 in) tall, and he physically stood out amongst his peers.^[12] He won the 200 m, in a time of 20.61 s,^[24] 0.03 seconds slower than his personal best of 20.58 s set in the 1st round.^[25] Bolt's 200 m win made him the youngest world-junior gold medalist ever.^[26] The expectation from the home crowd had made him so nervous that he had put his shoes on the wrong feet. However, it turned out to be a revelatory experience for Bolt as he vowed never again to let himself be affected by pre-race nerves.^[27] As a member of the Jamaican sprint relay team, he also took two silver medals and set national junior records in the 4×100 metres and 4×400 metres relay, running times of 39.15 s and 3:04.06 minutes respectively.^[28][29]

The flow of medals continued as he won four gold medals at the 2003 CARIFTA Games, and was awarded the Austin Sealy Trophy for the most outstanding athlete of the games.^[30][31][32] He won another gold at the 2003 World Youth Championships. He set a new championship record in the 200 m with a time of 20.40 s, despite a 1.1 m/s head wind.^[33] Michael Johnson, the 200 m world-record holder, took note of Bolt's potential but worried that the young sprinter might be over-pressured, stating, "It's all about what he does three, four, five years down the line".^[34] Bolt had also impressed the athletics hierarchy, and he received the IAAF Rising Star Award for 2002.^[35]

Bolt turned his main focus to the 200 m and equalled Roy Martin's world junior record of 20.13 s at the Pan-American Junior Championships.^[12][36] This performance attracted interest from the press, and his times in the 200 m and 400 m led to him being touted as a possible successor to Johnson. Indeed, at sixteen years old, Bolt had reached times that Johnson did not register until he was twenty, and Bolt's 200 m time was superior to Maurice Greene's season's best that year.^[34]

In his final Jamaican High School Championships in 2003, he broke both the 200 m and 400 m records with times of 20.25 s and 45.30 s, respectively. Bolt's runs were a significant improvement upon the previous records, beating the 200 m best by more than half a second and the 400 m record by almost a second.^[12]

Bolt was growing more popular in his homeland. Howard Hamilton, who was given the task of Public Defender by the government, urged the JAAA to nurture him and prevent burnout, calling Bolt "the most phenomenal sprinter ever produced by this island".^[34] His popularity and the attractions of the capital city were beginning to be a burden to the young sprinter. Bolt was increasingly unfocused on his athletic career and preferred to eat fast food, play basketball, and party in Kingston's club scene. In the absence of a disciplined lifestyle, he became ever-more reliant on his natural ability to beat his competitors on the track.^[37]

As the reigning 200 m champion at both the World Youth and World Junior championships, Bolt hoped to take a clean sweep of the world 200 m championships in the Senior World Championships in Paris.^[12] Bolt beat all comers at the 200 m in the World Championship trials, but he was pragmatic about his chances and noted that, even if he did not make the final, he would consider setting a personal best a success.^[34][38] However, he suffered a bout of conjunctivitis before the event, and it ruined his training schedule.^[12] Realising he would not be in peak condition, the JAAA refused to let him participate in the finals on the grounds that he was too young and inexperienced. Bolt was dismayed at missing out on the opportunity, but focused on getting himself in shape to gain a place on the Jamaican Olympic team instead.^[38] Even though he missed the World Championships, Bolt was awarded the IAAF Rising Star Award for the 2003 season on the strength of his junior record-equalling run.^[35]

Professional athletics career[link]

Early Professional Career (2004 – 2007)[link]

Under the guidance of new coach Fitz Coleman, Bolt turned professional in 2004, beginning with the CARIFTA Games in Bermuda.^[12] He became the first junior sprinter to run the 200 m in under twenty seconds, taking the world junior record outright with a time of 19.93 s.^[12][26] For the second time in the role, he was awarded the Austin Sealy Trophy for the most outstanding athlete of the 2004 CARIFTA Games.^[39][30][31] A hamstring injury in May ruined Bolt's chances of competing in the 2004 World Junior Championships, but he was still chosen for the Jamaican Olympic squad.^[40] Bolt headed to the 2004 Athens Olympics with confidence and a new record on his side. However, he was hampered by a leg injury and was eliminated in the first round of the 200 metres with a disappointing time of 21.05 s.^[1][41] American colleges offered Bolt track scholarships on the strength of his performances, but the teenager from Trelawny refused them all, stating that he was content to stay in his homeland of Jamaica.^[15] Bolt instead chose the surroundings of the University of Technology, Jamaica, as his professional training ground, staying with the university's primitive track and weight room that had served him well in his amateur years.^[42]

Bolt at the Crystal Palace Meeting in 2007

The year 2005 signalled a fresh start for Bolt in the form of a new coach, Glen Mills, and a new attitude to athletics. Mills recognised Bolt's potential and aimed to cease the sprinter's unprofessional approach to the sport.^[41] Bolt began training with Mills in preparation for the upcoming athletics season, partnering with more-seasoned sprinters such as Kim Collins and Dwain Chambers.^[43] The year began well, and in July he knocked more than a third of a second off the 200 m CAC Championship record with a run of 20.03 s,^[44] then registered his 200 m season's best at London's Crystal Palace, running in 19.99 s.^[1] Misfortune awaited Bolt at the next major event, the 2005 World Championships in Helsinki. Bolt felt that both his work ethic and athleticism had much improved since the 2004 Olympics, and he saw the World Championships as a way to live up to expectations, stating, "I really want to make up for what happened in Athens. Hopefully, everything will fall into place".^[45] Bolt qualified with runs under 21 s, but he suffered an injury in the final, finishing in last place with a time of 26.27 s.^[41][46] Injuries were preventing him from completing a full professional athletics season, and the eighteen-year-old Bolt still had not proven his mettle in the major world-athletics competitions.^[47] Bolt was involved in a car accident in November, and although he suffered only minor facial lacerations, his training schedule was further upset.^[48][49] His manager, Norman Peart, made Bolt's training less intensive, and he had fully recuperated the following week.^[48] Bolt had continued to improve his performances, and he reached the world top-5 rankings in 2005 and 2006.^[12] Peart and Mills stated their intentions to push Bolt to do longer sprinting distances with the aim of making the 400 m event his primary event by 2007 or 2008. Bolt was less enthusiastic, and demanded that he feel comfortable in his sprinting.^[48][50] He suffered another hamstring injury in March 2006, forcing him to withdraw from the 2006 Commonwealth Games in Melbourne, and he did not return to track events until May.^[51] After his recovery, Bolt was given new training exercises to improve flexibility, and the plans to move him up to the 400 m event were put on hold.^[47]

Upon his return to competition, the 200 m remained his primary event, and he beat Justin Gatlin's meet record in Ostrava, Czech Republic. Bolt had aspired to run under twenty seconds to claim a season's best but, despite the fact that bad weather had impaired his run, he was happy to end the meeting with just the victory.^[52] However, a sub-20-second finish was soon his, as he set a new personal best of 19.88 s at the 2006 Athletissima Grand Prix in Lausanne, Switzerland, finishing behind Xavier Carter and Tyson Gay to earn a bronze medal.^[53] Bolt had focused his athletics aims, stating that 2006 was a year to gain experience. Also, he was more keen on competing over longer distances, setting his sights on running regularly in both 200 m and 400 m events within the next two years.^[52] Bolt claimed his first major world medal two months later at the IAAF World Athletics Final in Stuttgart, Germany. He passed the finishing post with a time of 20.10 s, gaining a bronze medal in the process.^[1] The IAAF World Cup in Athens, Greece, yielded Bolt's first senior international silver medal.^[1] Wallace Spearmon from the United States won gold with a championship record time of 19.87 s, beating Bolt's respectable time of 19.96 s.^[54] Further 200 m honours on both the regional and international stages awaited Bolt in 2007. The young Jamaican yearned to run in the 100 metres, but coach Mills diverted his attention, stating that he could run the shorter distance if he broke the 200 m national record.^[41] In the Jamaican Championships, he ran 19.75 s in the 200 m, breaking the 36-year-old Jamaican record held by Don Quarrie by 0.11 s.^[12][15]

Mills complied with Bolt's demand to run in the 100 m, and he was entered to run the event at the 23rd Vardinoyiannia meeting in Rethymno, Crete. In his debut tournament run, he set a personal best of 10.03 s, winning the gold medal and feeding his enthusiasm for the event.^[15][55]

Bolt (second from left) behind Gay in the closing stages of the 200 m race

Bolt (left) on the podium with his silver medal from the 200 m race in Osaka (2007)

He built on this achievement at the 2007 World Championships in Osaka, Japan, winning a silver medal.^[1] Bolt recorded 19.91 s with a headwind of 0.8 m/s but this paled in comparison with Tyson Gay's time of 19.76 s, which set a new championship record.^[56]

The Jamaican national record fell when Bolt partnered with Asafa Powell, Marvin Anderson, and Nesta Carter in the 4×100 metres relay. However, their finish in 37.89 s was not enough to beat the Americans' time of 37.78 s.^[57] Bolt did not win any gold medals at the major tournaments in 2007, but Mills felt that Bolt's technique was much improved, pinpointing improvements in Bolt's balance at the turns over 200 m and an increase in his stride frequency, giving him more driving power on the track.^[41]

World-record breaker[link]

The silver medals from the 2007 Osaka World Championships boosted Bolt's desire to run, and he took a more serious, more mature stance towards his career.^[19] Bolt continued to develop in the 100 m, and he entered to run in the event at the Jamaica Invitational in Kingston. On 3 May 2008, Bolt ran a time of 9.76 s, aided by a tail wind of 1.8 m/s, considerably improving upon his previous personal best of 10.03 s.^[58] This was the second-fastest legal performance in the history of the event; second only to compatriot Asafa Powell's 9.74 s record set the previous year in Rieti, Italy.^[59] Rival Tyson Gay lauded the performance, praising Bolt's form and technique especially.^[60] Michael Johnson, who was observing the race, said that he was shocked at how quickly he had improved over the 100 m distance.^[61] The Jamaican surprised even himself with the time, but coach Glen Mills remained confident that there was more to come.^[60]

Bolt preparing ahead of a race at the 2007 Osaka World Championships

Mills' prediction came true before the end of the month when Bolt established a new 100 m world record on 31 May 2008. Pushed on by a tail wind of 1.7 m/s, Bolt ran 9.72 s at the Reebok Grand Prix held in the Icahn Stadium in New York City, breaking Powell's record.^[62] The record time was even more remarkable in light of the fact that it was only his fifth senior run over the distance.^[63] Gay again finished second and commended Bolt's physical superiority, stating, "It looked like his knees were going past my face".^[15] Commentators noted that Bolt appeared to have gained a psychological advantage over fellow Olympic contender Gay.^[41]

In June 2008, Bolt responded to claims that he was a lazy athlete, saying that the comments were unjustified, and he trained hard to achieve his potential. However, he surmised that such comments stemmed from his lack of enthusiasm for the 400 metres event, and chose to not make the effort to train for distance running.^[64] Turning his efforts to the 200 m, Bolt proved that he could excel in multiple events—first setting the world-leading time in Ostrava, then breaking the national record for the second time with a 19.67 s finish in Athens, Greece.^[65][66] Although Mills still preferred that Bolt focus on the longer distances, the acceptance of Bolt's demand to run in the 100 m worked for both sprinter and trainer. Bolt was more focused in practice, and a training schedule to boost his top speed and his stamina, in preparation for the Olympics, had improved both his 100 m and 200 m times.^[15][67][68] His confidence was building, and he was sure that he would perform well in the upcoming Olympics.^[65]

2008 Summer Olympics[link]

Bolt announced that he would double-up with the 100 metres and 200 metres events at the Beijing Summer Olympics, and the new 100 m world-record holder was the favourite to win both.^[69][70] Michael Johnson, the 200 m and 400 m record holder, personally backed the sprinter, saying that he did not believe that a lack of experience would work against him.^[71] Bolt qualified for the 100 m final with times of 9.92 s and 9.85 s in the quarter-finals and semifinals, respectively.^[72][73][74]

Bolt held a considerable lead over his rivals in the closing stages of the 100 m final.

In the Olympic 100 m final, Bolt broke new ground, winning in 9.69 s (unofficially 9.683 s) with a reaction time of 0.165 s.^[75] This was an improvement upon his own world record, and he was well ahead of second-place finisher Richard Thompson, who finished in 9.89 s.^[76] Not only was the record set without a favourable wind (+0.0 m/s), but he also visibly slowed down to celebrate before he finished and his shoelace was untied.^[77][78][79] Bolt's coach reported that, based upon the speed of Bolt's opening 60 m, he could have finished with a time of 9.52 s.^[80] After scientific analysis of Bolt's run by the Institute of Theoretical Astrophysics at the University of Oslo, Hans Eriksen and his colleagues also predicted a sub 9.60 s time. Considering factors such as Bolt's position, acceleration and velocity in comparison with second-place-finisher Thompson, the team estimated that Bolt could have finished in 9.55±0.04 s had he not slowed to celebrate before the finishing line.^[81][82]

Bolt stated that setting a record was not a priority for him, and that his goal was just to win the gold medal, Jamaica's first of the 2008 Games.^[83] Olympic medalist Kriss Akabusi construed Bolt's chest slapping before the finish line as showboating, noting that the actions cost Bolt an even faster record time.^[84] IOC president Jacques Rogge also condemned the Jamaican's actions as disrespectful.^[85][86] Bolt denied that this was the purpose of his celebration by saying, "I wasn't bragging. When I saw I wasn't covered, I was just happy".^[87] Lamine Diack, president of the IAAF, supported Bolt and said that his celebration was appropriate given the circumstances of his victory. Jamaican government minister Edmund Bartlett also defended Bolt's actions, stating, "We have to see it in the glory of their moment and give it to them. We have to allow the personality of youth to express itself".^[88]

Bolt leads the field in the closing stages of the 200 m final

Bolt then focused on attaining a gold medal in the 200 m event, aiming to emulate Carl Lewis' double win in the 1984 Los Angeles Olympics.^[89] Michael Johnson felt that Bolt would easily win gold but believed that his own world record of 19.32 s set at the 1996 Summer Olympics in Atlanta would remain intact at the Olympics.^[90] Bolt eased through the first and second rounds of the 200 m, jogging towards the end of his run both times.^[91] He won his semifinal and progressed to the final as the favourite to win.^[92] Retired Jamaican sprinter Don Quarrie praised Bolt, saying he was confident that Johnson's record could be beaten.^[35] The following day, at the final, he won Jamaica's fourth gold of the Games, setting a new world and Olympic record of 19.30 s.^[93] Johnson's record fell despite the fact that Bolt was impeded by a 0.9 m/s headwind. The feat made him the first sprinter since Quarrie to hold both 100 m and 200 m world records simultaneously and the first since the introduction of electronic timing.^[93][94] Furthermore, Bolt became the first sprinter to break both records at the same Olympics.^[95] Unlike in the 100 m final, Bolt sprinted hard all the way to the finishing line in the 200 m race, even dipping his chest to improve his time.^[96] Following the race, "Happy Birthday" was played over the stadium's sound system as his 22nd birthday would begin at midnight.^[96]

Two days later, Bolt ran as the third leg in the Jamaican 4x100 metres relay team, increasing his gold medal total to three.^[97] Along with teammates Nesta Carter, Michael Frater, and Asafa Powell, Bolt broke another world and Olympic record, their 37.10 s finish breaking the previous record by three tenths of a second.^[98] Powell, who anchored the team to the finishing line, lamented the loss of his 100 m record to Bolt but showed no animosity towards his Jamaican rival, stating that he was delighted to help him set his third world record.^[99] Following his victories, Bolt donated US$50,000 to the children of the Sichuan province of China to help those harmed by the 2008 Sichuan earthquake.^[100]