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Please Teacher!(Japanese:おねがい☆ティーチャー,Hepburn:Onegai Tīchā, Onegai ☆ Teacher) is an anime television series directed by Yasunori Ide, written by Yōsuke Kuroda, and produced by Bandai Visual. It was later adapted into a manga and light novel and centers on a group of friends and the odd things that happen to them after they get a new teacher.
The Please Teacher! anime series premiered in Japan on the WOWOW satellite television network between January 10 and March 28, 2002, spanning a total of 13 episodes, including twelve originally premiering on television plus an OVA episode released on DVD on October 25, 2002. It was adapted very soon into a manga, serialized in  MediaWorks's shōnen manga magazine, Dengeki Daioh, in January 2002, and was also later adapted into a light novel, entitled Onegai Teacher: Mizuho and Kei's Milky Diary, published in March 2003.
The Please Teacher! anime series was soon continued with a spin-off sequel,[3] Please Twins!, which premiered on WOWOW between July 15 and October 14, 2003.
The setting of the series, though left unsaid in either anime or manga, is Lake Kizaki, located in Nagano, Japan, and the region and its surrounding locations are featured prominently and accurately across the series.[4] The novel states that the school the characters attend is the Nagano Prefectural Kizaki High School. This school is based upon the Old Matsumoto High School located in Agatanomori Park of Matsumoto, about an hour south of Lake Kizaki on the JR Ōito Line. The tower of which Kaede and Hyosuke stand upon can be found in Joyama Park on the northwest part of the city. It takes place some time after 2009.
Plot
Please Teacher! is a story mainly revolving around a tight-knit group of friends in high school and how they cope with several life-changing events that are never too far off from intimate relationships. The main character is a boy named Kei Kusanagi who suffers from a very rare disease which causes a comatose state referred to as a "standstill" whenever he is under severe emotional distress.
Before the beginning of the story, Kei, at 15 years of age, had fallen into a "standstill" lasting three years after witnessing the suicide of his elder sister. After recovering, he quietly moved away from home in order to avoid social difficulty due to his long absence, and began living with his uncle, a medical doctor, and aunt. Due to the strange nature of how he came to live there, Kei wanted to keep the situation a secret from his new friends for fear of being ostracized as being too old to associate with them. After Kei had established himself in his new surroundings and had entered into a close group of mutually supportive friends, a Galactic Federation starship had entered Earth's atmosphere stealthily, approached Honshū Island and landed surreptitiously in Lake Kizaki.
The story begins with Kei suffering a minor 'standstill' while in the vicinity of the lake, witnessing several unexplainable phenomena happening there, and then watching as a beautiful half-human alien named Mizuho Kazami materialize beside the shore. Kazami was sent to observe planet Earth by a seemingly benevolent Galactic Federation in order to prevent humans from making developmental mistakes. (Later, it is revealed that she had personal reasons; she wanted to see the home planet of her father, who had died when she was a child.) Kei, upon observing the materialization, attempts to escape the pursuing Kazami. Kazami is under strict orders to prevent her true identity and mission from being discovered. During his attempt to escape, Kei falls into the lake. Kazami rescues Kei and, using information from his identification, is able to return him home in secret. The next day, Kazami has become Kei's new homeroom teacher and next-door neighbor.
During assisting her in moving in, Kei suffers another standstill, and while in a weakened state explains his predicament to the compassionate Mizuho, who ends up revealing her own origins and purpose on Earth. Several accidental activations of Mizuho's teleport technology (which were inadvertently caused by Kei) eventually place Kei and Mizuho in a couple of compromising situations in front of his uncle and aunt and his school's headmaster, but Kei protects Mizuho from charges for an inappropriate relationship between student and teacher by impulsively stating that they are married, resulting in an actual civil marriage that later blossoms into genuine affection for each other. The headmaster relents, partly because he, too, had married a former student younger than himself and can understand their situation personally. Both are allowed to stay so long as they do not reveal their status to the other students, and do not engage in any public displays of affection.
The remainder of the series concerns the budding intimate relationships between the close friends, one of whom (Koishi Herikawa) is romantically interested in Kei, and another (Ichigo Morino) who has suffered even greater loss of time from the same disease as he has; the problems of having to maintain the secrecy of the marriage; an interfering parent and sibling visiting from the Galaxy  Federation; and Kei learning to overcome the ever-present threat of another lengthy 'standstill' stealing more of his life, particularly as he has fallen deeply in love with Mizuho and desperately wants to remain with her.
Eventually Kei falls into another major "standstill" and in order to bring him out of it, Mizuho has to use her technology which is against the law.  As a result, her status on Earth is revoked, she is banned from the planet and all memory of her is erased from everyone's, including Kei's, minds.  With the help of her mother and sister she sneaks back and is devastated to learn that Kei, who she is deeply in love with, has no memory of her.  While helping her move back in, Kei reveals that his memory has returned and the two express their love for each other and get married again.
Characters
Kei Kusanagi(草薙 桂,Kusanagi Kei)
Voiced by: Sōichirō Hoshi(Japanese); Dave Wittenberg (English)
Kei is an 18-year-old who retains a 15-year-old body after a three-year-long "standstill", which is a coma-like state that occurs during a time of extreme emotional distress. Standstills are derived from an unknown, possibly psychological, disease that Kei and his friend Ichigo Morino have. He tends to be a very frail, shy boy, not often wanting to assert himself when need be.
After observing the landing of a UFO while on the bank of the nearby lake and subsequently observing the alien on the lake shore, odd things begin happening to Kei in connection with this alien. The next day, Kei is surprised to find, like everyone else, that one of their teachers quit and a quick replacement was found which just happened to turn out to be the alien - Mizuho Kazami. After a few more encounters with each other, Kei is taken to her spaceship where the whole situation goes from bad to worse. Upon striking Marie, a tiny computer helper of Mizuho's, it effectively is unable to perform as well as it seemed to work, which often puts the characters in strange situations if they cannot rely on the help of Marie.
Eventually, after Kei and Mizuho are found in a locked storage room by Kei's uncle and the principal of the school, his uncle impulsively tells the principal that Kei and Mizuho are married. Later, Kei and Mizuho do get married, though only the paperwork is done while there was no official ceremony. This whole situation is kept secret from Kei's friends as Ichigo Morino constantly tries to pair Kei up with a friend of hers, Koishi, and all the while Kei and Mizuho's relationship and attraction for each other only grows. Kei also appears occasionally in the sequel Please Twins!, but as cameos.
Mizuho Kazami(風見 みずほ,Kazami Mizuho)
Voiced by: Kikuko Inoue(Japanese); Bridget Hoffman (English)
Mizuho is a 23-year-old half-Earthling who is visually indiscernible from a regular human being. She is very attractive, which, while garnering the attention of the various male characters in the show, does serve to protect her secret. She comes to Earth to monitor the planet, but inadvertently she was seen by Kei just as she was landing. This leads to a catastrophic set of events that while nearly killing them both leads to a bond materializing between Kei and Mizuho.  Although she did not trust him at first, she started to become attracted to Kei and eventually falls in love with him after they shared secrets about their past with one another. In a conversation with Mizuho's younger sister Maho, Kei learns that she is the youngest member of the GF Observers ever to gain a license. She is stripped of her surveyor status in episode twelve after violating several key tenets of GF Law in order to save Kei. Also from Maho we learn that Mizuho apparently has never had a romantic relationship, which is verified when she admits as much to Kei.
One of the main conflicts in the story involves Mizuho and how she tends to have great jealousy and misjudgment. While she underwent training prior to her arrival of Japanese and Earth history and customs, she was ill prepared for dealing with the social interactions of adolescents.  This trouble is further compounded by her almost childlike lack of understanding of romance initially.  She even went to such great lengths as to spy on Kei while he was hanging out with a friend from school, Koishi Herikawa, in a set-up date.  She does eventually realize her feelings for Kei once they begin living together and at later points of the series shows restraint and maturity that she at other times lacks.  Mizuho's character can almost be thought of as two personalities.  The first of a well-mannered school teacher who is soft spoken and kind.  The other, seen mostly with Kei and the Edajima's is more outgoing, opinionated, and even violent on some occasions.  This last point can be illustrated by the events of episode 13 where Mizuho's mother held Kei hostage in a hotel.
She loves to eat Pochy, a Japanese snack food that consists of a biscuit stick covered with chocolate. She eats Pochy because it reminds her of her dead father; an empty box of Pochy was all Mizuho has left of him. Her mother and sister are also seen eating it in several episodes. Pochy is a fictional version of an actual snack known as Pocky. Her catch phrase is "Saiyūsen jikō yo!" ("This is a priority one!"). She also appears as a regular character in the same school in the sequel series Please Twins!
Koishi Herikawa(縁川 小石,Herikawa Koishi)
Voiced by: Ayako Kawasumi(Japanese); Michelle Ruff (English)
She is one of Kei's close friends who also pursues a romantic relationship with Kei. Her parents own a grocery store and she often has to go to deliver food that people ordered.
Koishi has a happy-disposition to her personality and is only ever seen crying when it comes to matters that involve Kei. In time, she discovers that Kei has already committed his heart to someone else, and eventually grows close to her teacher Yamada, with whom she is eventually implied to have entered a romantic relationship on her own in episode 13. Also briefly appears as a cameo in Please Twins!
Ichigo Morino(森野 苺,Morino Ichigo)
Voiced by: Yukari Tamura(Japanese); Julie Ann Taylor (English)
An evidently shrewd young woman who is seemingly wise beyond her (apparent) years, and who associates with very few friends. Surprisingly, even though she resembles a diminutive 15-year-old or perhaps younger, her real age is 21; her physical development was stunted due to her "standstills", in the same way that they affect Kei. She had been in a "standstill" for 6 years. Ichigo's loss of time and her sense of life cruelly having passed her by due to the illness (she wistfully reveals to Kei that she has a younger sister who is now married and expecting a child) tends to cause her to have a much more cynical and serious demeanor than is normal for someone of her seeming age, which is sometimes commented upon by her (much younger) friends.
Her keen mind causes her to suspect the too-often 'coincidences' regarding their former teacher's departure, the new one's arrival and strange events in their neighborhood immediately after that to be connected, but her much younger and guile-less friends dismiss those connections. She also features in the sequel Please Twins! as a regular character, but with a much more mischievous behavior as class president and resembling a dictator, in fact the Morino's attitude from "Please Teacher" is completely opposite from "Please Twins" seeming that she chose (thanks to Kei) to enjoy her live to the fullest even after the 6 years she lost, the first time she shows that mischievous behaviour is in the after-credits scene of the OVA where she leaks Kei's apparent affairs with three different women.
Kaede Misumi(水澄 楓,Misumi Kaede)
Voiced by: Sayaka Ohara(Japanese); Melissa Fahn (English)
Also one of Kei's friends, Kaede tends to be a rather shy girl most of the time. Her physical characteristics include that she is one quarter Irish, tall (for a Japanese) and with red hair and freckles. Despite her shyness, during an accidental visit to her hotel room by a sleep-deprived Hyosuke, in which he mistakenly climbed into her bed, she awoke from a lightly inebriated slumber and claimed that he had appeared to her in a dream which now seems to have come true. She then sweetly confesses her love for him and proceeds to seduce him. The two become inseparable and are seen together throughout the series, to the point of being seen exiting a love hotel together in the OVA. Kaede also features in Please Twins! briefly.
Hyosuke Magumo(間雲 漂介,Magumo Hyōsuke)
Voiced by: Mitsuo Iwata(Japanese); Kirk Thornton (English)
Hyosuke aspires to attend college at Tokyo University and become a professional statesman, much like his brother. Hyousuke's demeanor is initially that of a shallow attention-seeker. Despite his attitude he is a hardworker even impressing his friend by his high scores.
He gets very confused after Kaede (half awake believing Hyosuke being a dream) sweetly confessed to him, he overcame that confusion thanks to Kei setting a meeting with her, unbeknown to him and even angering him to the point of almost hitting Kei, he manages to cool down himself in time and grants that his friend actually is doing the best for him, and he manages to talk to Kaede and after a minor hesitation the both proceed to start a relationship.
After he becomes romantically involved with Kaede,  a deeper and much more sensitive and reflective side is revealed. Kaede confirms to Ichigo and Koishi that the private Hyosuke is actually a very different person; of him, she says "He's a gentleman and he's sweet." Of Kei's group of friends, he tends to be the most hyperactive of them all and often does the strangest things too. Hyosuke also appears in Please Twins! briefly.
Matagu Shido(四道 跨,Shidō Matagu)
Voiced by: Hiroaki Miura(Japanese); Tony Schnur (English)
A rather serious student who is also into astronomy, Matagu seems to be the most hopeless of the cast, a classic 'nerd', never even getting to the point of gaining a girlfriend by the end of the series. He is much less confident and self-assured than Hyosuke, or even Kei, leading one to conclude that he suffers from crippling shyness. His stated fondest dream is to meet with 'an alien creature from outer space', totally unaware of the fact that his teacher certainly qualifies as such, and that he has had several conversations with his life's dream in a very normal setting. He even considered to confess his love to her, but his shyness put a halt to his plans. Matagu appears as a common comic relief character in Please Twins! He is portrayed as a pervert when his sister is around, who only appears in Please Twins!.
Minoru Edajima(江田島 みのる,Edajima Minoru)
Voiced by: Naoya Uchida(Japanese); Michael McConnohie (English)
Kei's uncle and doctor of the local clinic. Minoru is something of a lecherous rogue, continually making wolfish comments regarding the attractiveness of passing women. He even does within earshot of his wife, who often retaliates with a measured degree of physical violence. He is openly jealous of Kei's relationship with Mizuho and is more than a little perverted (in the Japanese sense of the word). Despite this, he often covers for and helps Kei and Mizuho out, such as moving Kei's possessions into the married couple's new apartment, purchasing a proper wedding ring for their private ceremony, and paying for an expensive hotel in Okinawa for their honeymoon.
Konoha Edajima(江田島 このは,Edajima Konoha)
Voiced by: Rei Sakuma(Japanese); Karen Strassman (English)
Kei's aunt and nurse of the local clinic. A warm, kind-hearted and quite attractive woman who puts up with her husband's behavior only so much before she starts to get really angry at him. It is evident that she is the more mature member of their pair, and is quite able to curb Minoru's wayward eye and lecherous comments with a significant look or gesture. She is not above using a small degree of force to cause her husband to 'heel' if his behavior gets too outrageous. She seems very sexually amorous towards her husband and loves him deeply. She is very supportive of Kei and Mizuho's relationship, backing Minoru's initial lie to the Headmaster about the couple being married, and then providing a second-hand wedding dress for Mizuho to wear in a private ceremony with only her, Mizuho, Kei and Minoru present.
Marie(まりえ)
Voiced by: Tomoko Kaneda(Japanese); Sandy Fox (English)
A quasi-organic master control program for Mizuho's ship. Totally self-repairing and maintenance free. Hovers around in an inner tube and on occasion plays a miniature guitar. Due to Kei fearfully striking 'him' during an initial escape attempt when Mizuho revealed her true identity, Marie's programming became scrambled, endangering both Kei and Mizuho. Communicating partly through indistinct sounds and through gestures, Marie is essentially a portable link to the ship's operating system. But 'he' is also capable of emotion, as witnessed by the romantic relationship formed between 'himself' and Miruru and his sorrow at their parting. Additionally, in the OVA they are implied to have sex, and both of them become embarrassed when they see others display affection. The implication provided in the series 'extras' is that Marie and Miruru are but extensions of the ships themselves, and thus are the ships. Marie also appears in Please Twins!, often eating a different brand from Pochy, called "Prech".
Masaomi Yamada(山田 正臣,Yamada Masaomi)
Voiced by: Tomokazu Sugita(Japanese); Tony Oliver (English)
A quiet and shaggy male teacher whose hobby is creating human-powered planes (one of which flies successfully in the final episode, earning him a trophy). At first he appears to be something of a physically developed nerd, obsessed with his hobby. Koishi delivers him meals from her parents' grocery store, and eventually both of them grow close; in episode 13 it is implied that they actually may have entered a romantic (and sexual) relationship. He trimmed his hair after Koishi states that he would be handsome if would do so, he forgets this after Mizuho gets forcefully removed from everyone memories after she is stripped of her rank still he remains his new neat look. Yamada appears occasionally in Please Twins!
Maho Kazami(風見 まほ,Kazami Maho)
Voiced by: Satomi Koorogi(Japanese); Sandy Fox (English)
Mizuho's little sister, who disapproves of Kei but eventually comes to accept him. Initially, she is incensed that a member of the powerful Galactic Federation's elite Observers (which it is revealed that Mizuho has the honor of being its youngest member) would stoop to marry such an evident primitive (conveniently overlooking the fact that she is ostensibly the product of just such a union, claiming that the only time that she had ever seen Mizuho cry was when their father died; the implication of wildly different growth rates between alien and human are suggested here, as Maho is much younger-looking than Mizuho and Mizuho had stated that she could barely recall her father's appearance). Maho even attempts to use Miruru to hurt Kei. During the process, she learns just how deeply Kei loves Mizuho and vice versa, and she relents, and later actually shows him a degree of affection with a stolen kiss, but she still possesses a playfully devious nature and is not above blackmailing Kei with videos of intercourse between him and Mizuho to get what she wants.
Hatsuho even states that Maho is in love with Kei as she possibly look him like the ideal boyfriend.
Hatsuho Kazami(風見 はつほ,Kazami Hatsuho)
Voiced by: Yumi Takada(Japanese); Wendee Lee (English)
Mizuho's mother, who is very fond of Kei. She is a self-assured, bold but subtly assertive woman. She is not above playfully teasing her oldest daughter and son-in-law, demanding to know intimate details regarding their relationship. She greatly resembles Mizuho, with the exception of having purplish hair instead of magenta, green eyes and a small beauty mark on her chin.
Shirou Kazami(風見 士郎,Kazami Shirō)Mizuho's father and a Japanese astronaut; no image of him has ever been seen in the series. The 2009 Mars expedition ship he was a crew member of was presumed lost in space. However, a GF vessel rescued the crew, but the (never verified) implication was that he was not allowed to return to Earth. One of the crew of the GF spacecraft that rescued the Mars expedition was Hatsuho, which is how they came to meet and be married. Unable (or unwilling) to return to Earth, possibly due to the Federation's strict laws governing contact with non-incorporated races, he remained in Federation space and raised a family there. The assumption is that he had attained citizenship, either through marriage or through naturalization, and at that point may have been abjured from returning. Eventually, he went on to develop a planetary contact program for Earth for the Galactic Federation. He died when Mizuho was still a child. The only thing of Earth that he had left behind had been an empty box of Pochy, which Mizuho had treasured.
Miruru(みるる)
Voiced by: Michelle Ruff
Another computer intelligence hologram and Maho's sister, dressed in female-like clothing. The implication is that both Marie and Miruru are in fact commlinks for the ships, themselves. In other words, the ships house self-aware AIs capable of emotions, which are reflected in the actions of the two miniature beings. Seems also to be romantically involved with Marie. Like her counterpart, Miruru lacks human language, instead she utters "Miru" at random opposing to Marie's high-pitched shriek-like cries.
Kozue Kusanagi(草薙 こずえ,Kusanagi Kozue)
Voiced by: Omi Minami(Japanese); Julie Anne Taylor (English)
Kei Kusanagi's elder sister. In a flashback which is shown during a critical 'standstill', it is revealed that Kozue was a very bright, though possibly mentally disturbed, girl who felt that human emotions were the cause of much suffering in the world, and sought to escape them by committing suicide, which Kei had the misfortune of witnessing. The trauma of having done so and the guilt that he had felt at being unable to prevent it led to his first 'standstill'.
Natchan
Voiced by: Chinami Nishimura(Japanese); Wendee Lee (English)
Known as the little girl during the summer who finds a boy (Kei in this anime, Maiku in Please Twins!) who she quickly becomes attracted to. Soon after, she finds out the person she falls in love with already has a love interest. Her dog is then pulled on the neck by the leash when she staggers away broken-hearted. She also appears in Please Twins!
Media
Anime
The Please Teacher! anime series, authored and scripted by Yousuke Kuroda, directed by Yasunori Ide,[5] and produced by Bandai Visual, Studio Orphee and Daume, originally premiered in Japan on the satellite television network WOWOW, between January 10 and March 28, 2002, spanning a total of thirteen episodes, including twelve originally premiering on television plus an OVA episode concluding the series, released on DVD on October 25, 2002.
It has also been broadcast across Japan by the anime satellite television network, Animax, who have aired the series across its respective networks worldwide, including East Asia, Latin America, and as well as its English language networks in Southeast Asia and South Asia. The series has been licensed for North American distribution by Bandai's distributive unit across the region, Bandai Entertainment, who have released the series via a four-volume DVD release, and whose English dub has also been broadcast by Animax across its English-language networks in Southeast Asia and South Asia. The series is now licensed by Right Stuf under their Nozomi Entertainment label.
The Please Teacher! anime series was soon continued with a spinoff, Please Twins!, which premiered on WOWOW between July 15 and October 14, 2003, featuring many of the characters featured in the series, as the series' story happens after Please Teacher!.
The series' opening theme is "Shooting Star" by Kotoko, and the ending theme is "Sora no Mori de"(空の森で,In the Forest of the Sky) by Mami Kawada. The song "Sora wa Kataranai"(そらは語らない) by Kikuko Inoue is used as an insert song in episode 11, and the song "Love a Riddle" by Kotoko is used as the ending theme in episode 12.

Episodes

Manga
Please Teacher! was adapted into a manga series, authored by Japanese manga artist Shizuru Hayashiya, which was serialized in  MediaWorks's manga magazine, Dengeki Daioh, in January 2002, its run consisting of two-bound volume compilations. The manga has since been licensed for North American distribution by ComicsOne and in Brazil by Editora JBC.
The story maintains the basic plot, but adds comic humor that suits the manga format well, taking full advantage of still frames. However, there are quite a few minor details that have been omitted from the anime or were completely changed: the relationship between Hyosuke and Kaede is deflected, with Hyosuke ending up with Ichigo; Yamada is never introduced; Minoru is much more overt with his lecherousness, but is a great deal of help in Kei and Mizuho's relationship; Koishi's role is diminished somewhat; Hatsuho is only shown in only two frames, as a transmission call to the couple warning them of Maho's wrath and in the other world when Kei has a standstill; and finally, the Okinawan honeymoon is never shown or mentioned.
Light novel
The light novel version entitled Onegai Teacher: Mizuho and Kei's Milky Diary was written by Gō Zappa and illustrated by Taraku Uon and Hiroaki Gōda. It was published in Japan by MediaWorks in March 2003 and was only one volume in length. The English edition was released by Comics One in October 2003.
See also
Please Twins!
Waiting in the Summer
Notes and references

 (in Japanese)
 (in Japanese)
 (in Japanese)

 (anime) at Anime News Network's encyclopedia

What station did the Please Teacher! anime show first air on?


Metrication or metrification is conversion to the metric system of units of measurement.[2] Worldwide, there has been a long process of independent conversions of countries from various local and traditional systems, beginning in France during the 1790s and spreading widely over the following two centuries, but the metric system has not been fully adopted in all countries and sectors.

Overview
Whilst most countries in the world are using the metric system as their official system of weights and measures, some countries have not committed to adopting it, or have adopted it as their official system but have not completed the process of full metrication.
Most countries have adopted the metric system officially over a transitional period where both units are used for a set period of time. Some countries such as Guyana, for example, have officially adopted the metric system, but have had some trouble over time implementing it.[3] Antigua and Barbuda, also "officially" metric, is moving toward total implementation of the metric system, but slower than expected. The government had announced that they have plans to convert their country to the metric system by the first quarter of 2015.[4] Other Caribbean countries such as Saint Lucia are officially metric but are still in the process toward full conversion.[5]  In the United Kingdom the metric system is the official system for most regulated trading by weight or measure purposes, but some imperial units remain the primary official unit of measurement. As of 2018 the UK has only partially metricated.
According to the US Central Intelligence Agency's online The World Factbook (2016), the metric system has not been adopted by Myanmar (also known as Burma), Liberia and the US.[6] The United States (and its associated states; the Federated States of Micronesia, Marshall Islands and Palau)) officially use US customary units as does Liberia.[7] Myanmar officially uses the Burmese units of measurement. According to The [Liberian] Observer, Liberia are committed to adopting the metric system in the future.[7] Some sources now identify Liberia as metric, and the government of Myanmar has stated that the country would metricate with a goal of completion by 2019.[8][9] Both Myanmar and Liberia are substantially metric countries, trading internationally in metric units. Sierra Leone switched to selling fuel by the litre in May 2011.[10]
The European Union used the Units of Measure Directive to attempt to achieve a common system of weights and measures and to facilitate the European Single Market. Throughout the 1990s, the European Commission helped accelerate the process for member countries to complete their metric conversion processes. Among them is the United Kingdom where laws in some or all contexts mandate or permit many imperial measures, such as miles and yards for road-sign distances, road speed limits in miles per hour, pints of beer, and inches for clothes.[11] The United Kingdom secured permanent exemptions for the mile and yard in road markings, and (with Ireland) for the pint (Imperial) of draught beer sold in pubs[12] (see Metrication in the United Kingdom). In 2007, the European Commission also announced that (to appease British public opinion and to facilitate trade with the United States) it was to abandon the requirement for metric-only labelling on packaged goods, and to allow dual metric–imperial marking to continue indefinitely.[12]
The United States, the United Kingdom, and Canada have some active opposition to metrication, particularly where updated weights and measures laws would make obsolete historic systems of measurement.  Other countries, like France and Japan, that once had significant popular opposition to metrication now have complete acceptance of metrication.
Before the metric system

The Roman empire used the pes (foot) measure. This was divided into 12<i data-parsoid='{"dsr":[9064,9074,2,2]}'>unciae ("inches"). The libra ("pound") was another measure that had wide effect on European weight and currency long after Roman times, e.g. lb, £. The measure came to vary greatly over time. Charlemagne was one of several rulers who launched reform programmes of various kinds to standardise units for measure and currency in his empire, but there was no real general breakthrough.
In medieval Europe, local laws on weights and measures were set by trade guilds on a city-by-city basis. For example, the ell or elle was a unit of length commonly used in Europe, but its length varied from 40.2centimetres in one part of Germany to 70centimetres in The Netherlands and 94.5centimetres in Edinburgh. A survey of Switzerland in 1838 revealed that the foot had 37 different regional variations, the ell had 68, there were 83 different measures for dry grain, 70 measures for fluids and 63 different measures for "dead weights".[13] When Isaac Newton wrote Philosophiae Naturalis Principia Mathematica in 1687, he quoted his measurements in Parisian feet so readers could understand the size. Examples of efforts to have local intercity or national standards for measurements include the Scottish law of 1641, and the British standard imperial system of 1824, which is still commonly used in the United Kingdom. At one time Imperial China had successfully standardised units for volume throughout its territory, but by 1936 official investigations uncovered 53 values for the chi varying from 200millimetres to 1250millimetres; 32 values of the cheng, between 500millilitres and 8litres; and 36 different tsin ranging from 300grams to 2500grams.[14] However, revolutionary France was to produce the definitive International System of Units which has come to be used by most of the world today.
The desire for a single international system of measurement came from growing international trade and the need to apply common standards to goods. For a company to buy a product produced in another country, they need to ensure that the product would arrive as described. The medieval ell was abandoned in part because its value could not be standardised. One primary advantage of the International System of Units is simply that it is international, and the pressure on countries to conform to it grew as it became increasingly an international standard. However, it also simplified the teaching and learning of measurement as all SI units are based on a handful of base units (in particular, the metre, kilogram and second cover the majority of everyday measurements), using decimal prefixes to cover all magnitudes. This contrasts with pre-metric units, which largely have names that do not relate directly to one another (e.g. inch, foot, yard, mile) and are related to one another by inconsistent ratios which must simply be memorised (e.g. 12, 3, 1760). As the values in an SI expression are always decimal (i.e. without vulgar fractions) and mixed units (such as "feet and inches") are not used with SI, measurements are easy to add or multiply. Moreover, scientific measurement and calculation are greatly simplified as the units for electricity, force etc. are part of the SI system and hence are all interrelated in a coherent manner (e.g. 1J = 1kg·m2·s−2 = 1V·A·s). Standardisation of measures has contributed significantly to the industrial revolution and technological development in general. SI is not the only example of international standardisation; several powerful international standardisation organisations exist for various industries, such as the International Organisation for Standardisation (ISO), the International Electrotechnical Commission (IEC), and the International Telecommunication Union (ITU).
Forerunners of the metric system
Decimal numbers are an essential part of the metric system, with only one base unit and multiples created on the decimal base, the figures remain the same. This simplifies calculations. Although the Indians used decimal numbers for mathematical computations, it was Simon Stevin who in 1585 first advocated the use of decimal numbers for everyday purposes in his booklet De Thiende (old Dutch for 'the tenth').  He also declared that it would only be a matter of time before decimal numbers were used for currencies and measurements. His notation for decimal fractions was clumsy, but this was overcome with the introduction of the decimal point, generally attributed to Bartholomaeus Pitiscus who used this notation in his trigonometrical tables (1595).[15]
In his Essay towards a Real Character and a Philosophical Language, published in 1668, John Wilkins proposed a system of measurement that was very similar in concept to today's metric system.  He proposed retaining the second as the basic unit of time and proposed that the length of a pendulum which crossed the zero position once a second (i.e. had a period of two seconds) should be the base unit of length.  This length, for which he proposed the name "standard", would have been 994mm.  His base unit of mass, which he proposed calling a "hundred", would have been the mass of a cubic standard of distilled rainwater.  The names that he proposed for decimal multiples and subunits of his base units of measure were the names of units of measure that were in use at the time.[16][17]
In 1670, Gabriel Mouton published a proposal that was in essence similar to Wilkins' proposal, except that his base unit of length would have been 1/1000 of a minute of arc (about 1.852m) of geographical latitude.  He proposed calling this unit the virga.  Rather than using different names for each unit of length, he proposed a series of names that had prefixes, rather like the prefixes found in SI.[18]
In 1790, Thomas Jefferson submitted a report to the United States Congress in which he proposed the adoption of a decimal system of coinage and of weights and measures.  He proposed calling his base unit of length a "foot" which he suggested should be either 3⁄10 or 1⁄3 of the length of a pendulum that had a period of one second – that is 3⁄10 or 1⁄3 of the "standard" proposed by Wilkins over a century previously.  This would have equated to 11.755 English inches (29.8cm) or 13.06 English inches (33.1cm). Like Wilkins, the names that he proposed for multiples and subunits of his base units of measure were the names of units of measure that were in use at the time.[19] The great interest in geodesy during this era, and the measurement system ideas that developed, influenced how the continental US was surveyed and parceled. The story of how Jefferson's full vision for the new measurement system came close to displacing the Gunter chain and the traditional acre, but ended up not doing so, is explored in Andro Linklater's Measuring America.[20]
Adoption of metric weights and measures
During the nineteenth century the metric system of weights and measures proved a convenient political compromise during the unification processes in the Netherlands, Germany and Italy. In 1814, Portugal became the first country not part of the French Empire to officially adopt a metric system. Spain found it expedient in 1858 to follow the French example and within a decade Latin America had also adopted the metric system. There was considerable resistance to metrication in the United Kingdom and in the United States, though once the United Kingdom announced its metrication program in 1965, the Commonwealth followed suit.
France

The introduction of the metric system into France in 1795 was done on a district by district basis with Paris being the first district, but by modern standards the transition was poorly managed. Although thousands of pamphlets were distributed, the Agency of Weights and Measures who oversaw the introduction underestimated the work involved. Paris alone needed 500,000 metre sticks, yet one month after the metre became the sole legal unit of measure, they only had 25,000 in store.[21]: 269 This, combined with other excesses of the Revolution and the high level of illiteracy made the metric system unpopular.
Napoleon himself ridiculed the metric system, but as an able administrator, recognised the value of a sound basis for a system of measurement and under the décret impérial du 12 février 1812 (imperial decree of 12 February 1812), a new system of measure – the mesures usuelles or "customary measures" was introduced for use in small retail businesses – all government, legal and similar works still had to use the metric system and the metric system continued to be taught at all levels of education.[22] The names of many units used during the ancient regime were reintroduced, but were redefined in terms of metric units. Thus the toise was defined as being two metres with six pied making up one toise, twelve pouce making up one pied and twelve lignes making up one pouce. Likewise the livre was defined as being 500g, each livre comprising sixteen once and each once eight gros and the aune as 120 centimetres.[23]
Louis Philippe I by means of the La loi du 4 juillet 1837 (the law of 4 July 1837) effectively revoked the use of mesures uselles by reaffirming the laws of measurement of 1795 and 1799 to be used from 1 May 1840.[24][25] However, many units of measure, such as the livre (for half a kilogram), remained in everyday use for many years,[25][26] and to a residual extent up to this day.
Germany

At the outbreak of the French Revolution, much of modern-day Germany and Austria were part of the Holy Roman Empire which had become a loose federation of kingdoms, principalities, free cities, bishoprics and other fiefdoms, each with its own system of measurement, though in most cases such system were loosely derived from the Carolingian system instituted by Charlemagne a thousand years earlier.
During the Napoleonic era, there was a move among some of the German states to reform their systems of measurement using the prototype metre and kilogram as the basis of the new units. Baden, in 1810, for example, redefined the Ruthe (rods) as being 3.0m exactly and defined the subunits of the Ruthe as 1 Ruthe = 10<i data-parsoid='{"dsr":[23662,23669,2,2]}'>Fuß (feet) = 100<i data-parsoid='{"dsr":[23688,23696,2,2]}'>Zoll (inches) = 1,000Linie (lines) = 10,000Punkt (points) while the Pfund was defined as being 500g, divided into 30Loth, each of 16.67g.[27][28] Bavaria, in its reform of 1811, trimmed the Bavarian Pfund from 561.288g to 560g exactly, consisting of 32 Loth, each of 17.5g[29] while the Prussian Pfund remained at 467.711g.[30]
After the Congress of Vienna there was a degree of commercial cooperation between the various German states resulting in the setting of the German Customs Union (Zollverein). There were however still many barriers to trade until Bavaria took the lead in establishing the General German Commercial Code in 1856. As part of the code the Zollverein introduce the Zollpfund (Customs Pound) which was defined to be exactly 500g and which could be split into 30'lot'.[31] This unit was used for inter-state movement of goods, but was not applied in all states for internal use.
Although the Zollverein collapsed after the Austro-Prussian War of 1866, the metric system became the official system of measurement in the newly formed German Empire in 1872[21]:350 and of Austria in 1875.[32] The Zollpfund ceased to be legal in Germany after 1877.[33]
Italy

The Cisalpine Republic, a North Italian republic set up by Napoleon in 1797 with its capital at Milan first adopted a modified form of the metric system based in the braccio cisalpino (Cisalpine cubit) which was defined to be half a metre.[34] In 1802 the Cisalpine Republic was renamed the Italian Republic, with Napoleon as its head of state. The following year the Cisalpine system of measure was replaced by the metric system.[34]
In 1806, the Italian Republic was replaced by the Kingdom of Italy with Napoleon as its emperor. By 1812, all of Italy from Rome northwards was under the control of Napoleon, either as French Departments or as part of the Kingdom of Italy ensuring the metric system was in use throughout this region.
After the Congress of Vienna, the various Italian states reverted to their original system of measurements, but in 1845 the Kingdom of Piedmont and Sardinia passed legislation to introduce the metric system within five years. By 1860, most of Italy had been unified under the King of Sardinia Victor Emmanuel II and under Law 132 of 28 July 28, 1861  the metric system became the official system of measurement throughout the kingdom. Numerous Tavole di ragguaglio (Conversion Tables) were displayed in shops until 31 December 1870.[34]
Netherlands
The Netherlands first used the metric system and then, in 1812, the mesures usuelles when it was part of the First French Empire. Under the Royal decree of 27 March 1817 (Koningklijk besluit van den 27 Maart 1817), the newly formed Kingdom of the Netherlands abandoned the mesures usuelles in favour of the "Dutch" metric system (Nederlands metrisch stelsel) in which metric units were simply given the names of units of measure that were then in use. Examples include the ons (ounce) which was defined as being 100g.[35]
Portugal
In August 1814, Portugal officially adopted the metric system but with the names of the units substituted by Portuguese traditional ones. In this system the basic units were the mão-travessa (hand) = 1decimetre (10<i data-parsoid='{"dsr":[31549,31566,2,2]}'>mão-travessas = 1<i data-parsoid='{"dsr":[31576,31584,2,2]}'>vara (yard) = 1metre), the canada = 1liter and the libra (pound) = 1kilogram.[36]
Spain
Until the ascent of the Bourbon monarchy in Spain in 1700, each of the regions of Spain retained its own system of measurement. The new Bourbon monarchy tried to centralise control and with it the system of measurement. There were debates regarding the desirability of retaining the Castilian units of measure or, in the interests of harmonisation, adopting the French system.[37] Although Spain assisted Méchain in his meridian survey, the Government feared the French revolutionary movement and reinforced the Castilian units of measure to counter such movements. By 1849 however, it proved difficult to maintain the old system and in that year the metric system became the legal system of measure in Spain.[37]The Government was urged by the Spanish Royal Academy of Science to approve the creation of a large-scale map of Spain in 1852. The following year Carlos Ibáñez e Ibáñez de Ibero was appointed to undertake this task. All the scientific and technical material had to be created. Carlos Ibáñez e Ibáñez de Ibero and Saavedra went to Paris to supervise the production by Brunner of a measuring instrument which they had devised and which they later compared with Borda's double-toise N°1 which was the main reference for measuring all geodetic bases in France and whose length was 3.8980732 metres.
In 1865 the triangulation of Spain was connected with that of Portugal and France. In 1866 at the conference of the Association of Geodesy in Neuchâtel, Ibáñez announced that Spain would collaborate in remeasuring the French meridian arc. In 1879 Ibáñez and François Perrier (representing France) completed the junction between the geodetic network of Spain and Algeria and thus completed the measurement of the French meridian arc which extended from Shetland to the Sahara.
In 1867 Russia, Spain and Portugal joined the "Europäische Gradmessung" (European Arc Measurement which would become the International Association of Geodesy). This same year at the second general conference of the European Arc Measurement held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth. The conference recommended the adoption of the metre and the creation of an international metre commission, according to the proposal of Johann Jacob Baeyer, Adolphe Hirsch and Carlos Ibáñez e Ibáñez de Ibero.
In November 1869 the French government issued invitations to join this commission. Spain accepted and Carlos Ibáñez e Ibáñez de Ibero took part in the Committee of preparatory research from the first meeting of the  in 1870. He became president of the permanent Committee of the International Metre Commission in 1872. In 1874 he was elected as president of the Permanent Commission of the European Arc Measurement. He also presided the General Conference of the European Arc Measurement held in Paris in 1875, when the association decided the creation of an international geodetic standard for the bases' measurement.[38] He represented Spain at the 1875 conference of the Metre Convention, which was ratified the same year in Paris. The Spanish geodesist was elected as the first president of the International Committee for Weights and Measures. His activities resulted in the distribution of a platinum and iridium prototype of the metre to all States parties to the Metre Convention during the first meeting of the General Conference on Weights and Measures in 1889. Theses prototypes defined the metre right up until 1960.
United Kingdom
In 1824 the Weights and Measures Act imposed one standard 'imperial' system of weights and measures on the British Empire.[39] The effect of this act was to standardise existing British units of measure rather than to align them with the metric system.
During the next eighty years a number of Parliamentary select committees recommended the adoption of the metric system, each with a greater degree of urgency, but Parliament prevaricated. A Select Committee report of 1862 recommended compulsory metrication, but with an "Intermediate permissive phase"; Parliament responded in 1864 by legalising metric units only for 'contracts and dealings'.[40] The United Kingdom initially declined to sign the Treaty of the Metre, but did so in 1883. Meanwhile, British scientists and technologists were at the forefront of the metrication movement – it was the British Association for the Advancement of Science that promoted the CGS system of units as a coherent system[41]: 109 and it was the British firm Johnson Matthey that was accepted by the CGPM in 1889 to cast the international prototype metre and kilogram.[42]
In 1895 another Parliamentary select committee recommended the compulsory adoption of the metric system after a two-year permissive period. The 1897 Weights and Measures Act legalised the metric units for trade, but did not make them mandatory.[40] A bill to make the metric system compulsory in order to enable the British industrial base to fight off the challenge of the nascent German base passed through the House of Lords in 1904, but did not pass in the House of Commons before the next general election was called. Following opposition by the Lancashire cotton industry, a similar bill was defeated in 1907 in the House of Commons by 150 votes to 118.[40]
In 1965 Britain commenced an official programme of metrication that, as of 2012, had not been completed.
In the United Kingdom metric is the official system for most regulated trading by weight or measure purposes, but some imperial units remain the primary official unit of measurement. For example, miles, yards, and feet remain the official units for road signage – and use of imperial units is widespread.[43][21]  The Imperial pint also remains a permitted unit for milk in returnable bottles and for draught beer and cider in British pubs.[43] Imperial units are also legal for use alongside metric units on food packaging and price indications for goods sold loose, and may be used exclusively where a product is sold by description, rather than by weight/mass/volume. E.g. Television screen and clothing sizes tend to be denominated in inches only, but a piece of material priced per inch would be unlawful unless the metric price was also shown.
United States

In 1805 a Swiss geodesist Ferdinand Rudolph Hassler brought copies of the French metre and kilogram to the United States.[44] In 1830 the Congress decided to create uniform standards for length and weight in the United States.[45] Hassler was mandated to work out the new standards and proposed to adopt the metric system.[45] The Congress opted for the British Parlementiary Standard from 1758 and the Troy Pound of Great Britain from 1824 as length and weight standards.[45] Nevertheless the primary baseline of the US Coast Survey was measured in 1834 at Fire Island using four two-metre iron bars constructed after Hassler's specification in the United Kingdom and brought back in the United States in 1815.[46][47] All distances measured in the US National Geodetic Survey were referred to the metre.[48] In 1866 the United States Congress passed a bill making it lawful to use the metric system in the United States. The bill, which was permissive rather than mandatory in nature, defined the metric system in terms of customary units rather than with reference to the international prototype metre and kilogram.[49][50]:10–13 By 1893, the reference standards for customary units had become unreliable. Moreover, the United States, being a signatory of the Metre Convention was in possession of national prototype metres and kilograms that were calibrated against those in use elsewhere in the world. This led to the Mendenhall Order which redefined the customary units by referring to the national metric prototypes, but used the conversion factors of the 1866 act.[50]:16–20  In 1896 a bill that would make the metric system mandatory in the United States was presented to Congress. Of the 29 people who gave evidence before the congressional committee who were considering the bill, 23 were in favor of the bill, but six were against. Four of the six dissenters represented manufacturing interests and the other two the United States Revenue service. The grounds cited were the cost and inconvenience of the change-over. The bill was not enacted. Subsequent bills suffered a similar fate.[32]
The United States mandated the acceptance of the metric system in 1866 for commercial and legal proceedings, without displacing their customary units.[51]
In 1971 the US National Bureau of Standards completed a three-year study of the impact of increasing worldwide metric use on the US. The study concluded with a report to Congress entitled A Metric America – A Decision Whose Time Has Come. Since then metric use has increased in the US, principally in the manufacturing and educational sectors. Public Law 93-380, enacted 21 August 1974, states that it is the policy of the US to encourage educational agencies and institutions to prepare students to use the metric system of measurement with ease and facility as a part of the regular education program. On 23 December 1975, President Gerald Ford signed Public Law 94-168, the Metric Conversion Act of 1975. This act declares a national policy of coordinating the increasing use of the metric system in the US It established a US Metric Board whose functions as of 1 October 1982 were transferred to the Dept of Commerce, Office of Metric Programs, to coordinate the voluntary conversion to the metric system.[52]
In January 2007 NASA decided to use metric units for all future moon missions, in line with the practice of other space agencies.[53]
Other anglophone countries
The British metrication programme signalled the start of metrication programmes elsewhere in the Commonwealth, though India had started its programme in 1959, six years before the United Kingdom. South Africa (then not a member of the Commonwealth) set up a Metrication Advisory Board in 1967, New Zealand set up its Metric Advisory Board in 1969, Australia passed the Metric Conversion Act in 1970 and Canada appointed a Metrication Commission in 1971. Metrication in Australia, New Zealand and South Africa was essentially complete within a decade, while metrication in India and Canada is not complete. In addition the lakh and crore are still in widespread use in India, while in Canada the square foot is still widespread for commercial and residential advertisements and partially in construction because of the close trade relations with the United States, and the railways of Canada continue to measure their trackage in miles and speed limits in miles per hour because they also operate in the United States. Most other Commonwealth countries adopted the metric system during the 1970s.[54]
Countries, other than the United Kingdom, using the imperial system completed official metrication during the second half of the 20th century or the first decade of the 21st century. The most recent to complete this process was the Republic of Ireland, which began metric conversion in the 1970s and completed it in early 2005.[55]
Conversion process
The metric system was officially introduced in France in December 1799. In the 19th century, the metric system was adopted by almost all European countries: Portugal (1814);[36]
Netherlands, Belgium and Luxembourg (1820); Switzerland (1835); Spain (1850s); Italy (1861); Romania (1864); Germany (1870, legally from 1 January 1872);[56] and Austria-Hungary (1876, but the law was adopted in 1871).[32] Thailand did not formally adopt the metric system until 1923, but the Royal Thai Survey Department used it for cadastral survey as early as 1896.[57] Denmark and Iceland adopted the metric system in 1907.
Chronology and status of conversion by country

Links in the country point to articles about metrication in that country.[58]

Notes

There are three common ways that nations convert from traditional measurement systems to the metric system. The first is the quick, or "Big-Bang" route which was used by India in the 1960s and several other nations including Australia and New Zealand since then. The second way is to phase in units over time and progressively outlaw traditional units. This method, favoured by some industrial nations, is slower and generally less complete. The third way is to redefine traditional units in metric terms. This has been used successfully where traditional units were ill-defined and had regional variations.
The "Big-Bang" way is to simultaneously outlaw the use of pre-metric measurement, metricate, reissue all government publications and laws, and change education systems to metric. India's changeover lasted from 1 April 1960, when metric measurements became legal, to 1 April 1962, when all other systems were banned. The Indian model was extremely successful and was copied over much of the developing world.
The phase-in way is to pass a law permitting the use of metric units in parallel with traditional ones, followed by education of metric units, then progressively ban the use of the older measures.  This has generally been a slow route to metric.  The British Empire permitted the use of metric measures in 1873, but the changeover was not completed in most Commonwealth countries until the 1970s and 1980s when governments took an active role in metric conversion.  Japan also followed this route and did not complete the changeover for 70years.  In the United Kingdom, the process is still incomplete.  By law, loose goods sold with reference to units of quantity have to be weighed and sold using the metric system.  In 2001, the EU directive 80/181/EEC stated that supplementary units (imperial units alongside metric including labelling on packages) would become illegal from the beginning of 2010.  In September 2007,[12] a consultation process was started which resulted in the directive being modified to permit supplementary units to be used indefinitely.
The third method is to redefine traditional units in terms of metric values.  These redefined "quasi-metric" units often stay in use long after metrication is said to have been completed.  Resistance to metrication in post-revolutionary France convinced Napoleon to revert to mesures usuelles (usual measures), and, to some extent, the names remain throughout Europe.  In 1814, Portugal adopted the metric system, but with the names of the units substituted by Portuguese traditional ones.  In this system, the basic units were the mão-travessa (hand) = 1decimetre (10<i data-parsoid='{"dsr":[80349,80366,2,2]}'>mão-travessas = 1<i data-parsoid='{"dsr":[80376,80384,2,2]}'>vara (yard) = 1metre), the canada = 1litre and the libra (pound) = 1kilogram.[36]  In the Netherlands, 500g is informally referred to as a pond (pound) and 100g as an ons (ounce), and in Germany and France, 500g is informally referred to respectively as ein Pfund and une livre ("one pound").[88]  In Denmark, the re-defined pund (500g) is occasionally used, particularly among older people and (older) fruit growers, since these were originally paid according to the number of pounds of fruit produced.  In Sweden and Norway, a mil (Scandinavian mile) is informally equal to 10km, and this has continued to be the predominantly used unit in conversation when referring to geographical distances.  In the 19th century, Switzerland had a non-metric system completely based on metric terms (e.g. 1<i data-parsoid='{"dsr":[81720,81728,2,2]}'>Fuss (foot) = 30cm, 1<i data-parsoid='{"dsr":[81757,81765,2,2]}'>Zoll (inch) = 3cm, 1<i data-parsoid='{"dsr":[81793,81802,2,2]}'>Linie (line) = 3mm).  In China, the jin now has a value of 500g and the liang is 50g.
It is difficult to judge the degree to which ordinary people change to using metric in their daily lives.  In countries that have recently changed, older segments of the population tend to still use the older units.  Also, local variations abound in which units are round metric quantities or not.  In Canada, for example, ovens and cooking temperatures are usually measured in degrees Fahrenheit and Celsius.  Except for in cases of import items, all recipes and packaging include both Celsius and Fahrenheit, so Canadians are typically comfortable with both systems of measurement.  This extends to manufacturing, where companies are able to use both imperial and metric units, since the major export market is the US, but metric is required for both domestic use and for nearly all other exports.  This may be due to the overwhelming influence of the neighbouring United States; similarly, many Canadians still often use non-metric measurements in day-to-day discussions of height and weight, though most driver's licences and other official government documents record weight and height only in metric (Saskatchewan driver licences, prior to the introduction of the current one-piece licence, indicated height in feet and inches but have switched to centimetres following the new licence format).  In Canadian schools, however, metric is the standard, except when it comes up in recipes, where both are included, or in practical lessons involving measuring wood or other materials for manufacturing.  In the United Kingdom, degrees Fahrenheit are seldom encountered (except when some people talk about hot summer weather), while other metric units are often used in conjunction with older measurements, and road signs use miles rather than kilometres.  Another example is "hard" and "soft" metric.  Canada converted liquid dairy products to litre, 500mL, and 250mL sizes, which caused some complaining at the time of the conversion, as a litre of milk is slightly over 35 imperial fluid ounces, while the former imperial quart used in Canada was 40ounces.  This is an example of a "hard" metric conversion.  Conversely, butter in Canada is sold primarily in a 454g package, which converts to one Imperial pound. This is considered a "soft" metric conversion.
Exceptions

As of 2015, the metric system officially predominates in most countries of the world; some  traditional units, however, are still used in many places in specific industries.  For example:
Photo and video cameras are standardized to mount to tripods using 1⁄4-20 and 3⁄8-16 screws, which are dimensioned in inches, as per ISO 1222:2010.[89]
Automobile tyre pressure is commonly measured in units of psi in several countries including Brazil, Peru, Argentina, Australia, and Chile, the UK and the US.
Automotive engine power is usually measured in horsepower (rather than in kilowatts) in Russia, most other ex-USSR countries and German-speaking countries (note that this is typically "metric horsepower" rather than imperial horsepower), although in the EU from 2010 the horsepower is permitted only as a supplementary unit.[90]
In Hong Kong, traditional Chinese and British imperial units are normally used instead of metric units in particular types of trade.
Construction workers in Northern Europe often refer to planks and nails by their old inch-based names.
The length of small sail boats is often given in feet in popular conversation.
Office space is often rented in traditional units, such as square feet in Hong Kong and India, tsubo/pyeong/"ping" in Japan, Korea, and Taiwan.
In plumbing, some pipes and pipe threads are still designated in inch sizes due to historic international acceptance of particular sequences of pipe sizes and pipe threads, such as BSP / ISO 7 / EN 10226 threads.
In the United Kingdom and some Commonwealth countries, temperatures of domestic gas ovens are often specified using gas marks.[91][92] Similarly, older French ovens and recipes book often use a scale based on the Fahrenheit scale: "Thermostat" (abbreviated "Th"), where Thermostat 1 equals 100°F for conventional ovens, increasing by 50°F for each whole number along the scale.[93]
Automotive and bicycle wheel diameters are still usually but not always set as whole inch measurements (although tyre widths are measured in millimetres).
Dots per inch and pixels per inch continue to be used in describing graphical resolution in the computer and printing industry.
Thread count is frequently measured in "threads per inch" or "ends per inch".
Television and monitor screen diagonals are still commonly cited in inches in many countries; however, in countries such as Australia, France and South Africa, centimetres are often used for television sets, whereas CRT computer monitors and all LCD monitors are measured in inches.
Many large format computer printers, commonly known as plotters, have carriage widths measured in inches. Common widths are 24in (610mm), 36in (910mm), 44in (1,100mm) and 60in (1,500mm). While metric media sizes are often quoted (e.g. A0, A1), rolls of film, plain paper or photographic paper are normally sold in these widths, giving rise to wastage when they are trimmed. Rolls lengths are variously quoted in feet or metres.
In the electronic industry, the dominant spacing for components is based on intervals of 1⁄10in (2.54mm), and a change would lead to compatibility issues, e.g., for connectors.
Within the mechanical industry, inch-based spare parts can occasionally be kept, e.g., to service American or pre-World War II machines, but at maintenance, screws may be exchanged to metric thread.
In Ireland, the only legal exception to the metrication process was the pint (redefined as 570ml) in bars, pubs, and clubs (although alcohol sold in any other location is in metric units (usually 330ml (bottled beer), 500ml (canned beer), 750ml (wine), or 1L or 700ml (spirits))).
In Australia, a pint of beer was redefined to 570ml (see Australian beer glasses).
In both metric and non-metric countries, racing bicycle frames are generally measured in centimetres, while mountain bicycle and other frames are measured in either or both.
In the sport of surfing, surfboards are usually designed, constructed, and sold in feet and inches.
In Spain and former colonies i.e. Americas and Philippines certain pre-metric units are still used, e.g., the quiñón for land measurement in the Philippines, the fanega, ferrado and atahúlla to name three used in Spain and other former possessions.
The pulgada (inch) is 23mm, 2mm shorter than the English inch.
In many long-time metric countries, when non-metric units are used, it is often to give rough estimates in a short form, while accurate measures always are metric, e.g., "6feet" may feel less exact and shorter to say than "1.8metres" or "180cm". Measurement tools for inches are generally rare to find there, only on the other side of some carpenter's rulers, and may present a variation between national legacy inches and British/US inches, easily causing significant measurement errors if used.
The Imperial gallon is used as a unit of measure for fuel in Anguilla, Antigua and Barbuda, Burma, the Cayman Islands, Dominica, Grenada, Montserrat, St Kitts and Nevis and St Vincent and the Grenadines. In the United Kingdom fuel efficiency is officially recorded in miles per imperial gallon although fuel is sold in litres.
The US gallon is used in the Bahamas, Belize, British Virgin Islands, Colombia, Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Liberia, Peru, Turks and Caicos Islands, and the US, especially for pricing.
In Latin America, as SI units are standard, litres are used as well, e.g., often regarding fuel economy (km per litre), and the Spanish word galón may occasionally refer to a portable fuel container, often 5–20L.
Road distances and speed limits are still displayed in miles and miles per hour respectively in the USA, UK, Burma, and various Caribbean nations.[94]
Precious metals are often sold by troy weight, even in countries that otherwise use the metric system.[95]
In some countries (such as Antigua and Barbuda, see above), the transition is still in progress.  The Caribbean island nation of Saint Lucia announced metrication programmes in 2005 to be compatible with CARICOM.[96]
United Kingdom

In the United Kingdom, some of the population continue to resist metrication to varying degrees. The traditional imperial measures are preferred by a majority and continue to have widespread use in some applications.[97][98] The metric system is used by most businesses,[99] and is used for most trade transactions. Metric units must be used for certain trading activities (selling by weight or measure for example), although imperial units may continue to be displayed in parallel.[100]
British law has enacted the provisions of European Union directive 80/181/EEC, which catalogues the units of measure that may be used for "economic, public health, public safety and administrative purposes".[101] These units consist of the recommendations of the General Conference on Weights and Measures,[41] supplemented by some additional units of measure that may be used for specified purposes.[102] Metric units could be legally used for trading purposes for nearly a century before metrication efforts began in earnest. The government had been making preparations for the conversion of the Imperial unit since the 1862 Select Committee on Weights and Measures recommended the conversion[103] and the Weights and Measures Act of 1864 and the Weights and Measures (Metric System) Act of 1896 legalised the metric system.[104] In 1965, with lobbying from British industries and the prospects of joining the Common Market, the government set a 10-year target for full conversion, and created the Metrication Board in 1969. Metrication did occur in some areas during this time period, including the re-surveying of Ordnance Survey maps in 1970, decimalisation of the currency in 1971, and teaching the metric system in schools. No plans were made to make the use of the metric system compulsory, and the Metrication Board was abolished in 1980 following a change in government.[105]
The United Kingdom avoided having to comply with the 1989 European Units of Measurement Directive (89/617/EEC), which required all member states to make the metric system compulsory, by negotiating derogations (delayed switchovers), including for miles on road signs and for pints for draught beer, cider, and milk sales.[106]
Following the United Kingdom's referendum to exit the European Union, retailers have begun to request to go back to using Imperial Units, with some reverting without permission. A poll following the EU vote also found that 45% of Britons sought to revert to selling produce in Imperial Units.[107]
In popular conversation, the stone unit is widely used for measuring a person's weight and feet and inches for height.
United States and Canada

Over time, the metric system has influenced the United States through international trade and standardisation. The use of the metric system was made legal as a system of measurement in 1866[108] and the United States was a founding member of the International Bureau of Weights and Measures in 1875.[109] The system was officially adopted by the federal government in 1975 for use in the military and government agencies, and as preferred system for trade and commerce.[110] It has remained voluntary for federal and state road signage to use metric units, despite attempts in the 1990s to make it a requirement.[111]
A 1992 amendment to the Fair Packaging and Labeling Act (FPLA), which took effect in 1994, required labels on federally regulated "consumer commodities"[112] to include both metric and US customary units. As of 2013, all but one US state (New York) have passed laws permitting metric-only labels for the products they regulate.[113] Likewise, Canada also legally allows for dual labelling of goods provided that the metric unit is listed first and that there is a distinction of whether a liquid measure is a US or a Canadian (Imperial) unit.[114]
Today, the American public and much of the private business and industry still use US customary units despite many years of informal or optional metrication.[115] At least two states, Kentucky and California, have even moved towards demetrication of highway construction projects.[116][117][118]
Air and sea transportation

Air and sea transportation commonly use the nautical mile. This is about one minute of arc of latitude along any meridian arc and it is precisely defined as 1852metres (about 1.151 statute miles). It is not an SI unit (although it is accepted for use in the SI by the BIPM). The prime unit of speed or velocity for maritime and air navigation remains the knot (nautical mile per hour).
The prime unit of measure for aviation (altitude, or flight level) is usually estimated based on air pressure values, and in many countries, it is still described in nominal feet, although many others employ nominal metres.  The policies of the International Civil Aviation Organization (ICAO) relating to measurement are:
there should be a single system of units throughout the world
the single system should be the SI
the use of the foot for altitude is a permitted variation.
Consistent with ICAO policy, aviation has undergone a significant amount of metrication over the years. For example, runway lengths are usually given in metres. The United States metricated the data interchange format (METAR) for temperature reports in 1996.[119] Metrication is also gradually taking place in cargo weights and dimensions and in fuel volumes and weights.
In some countries like China, ex Soviet countries and Russia, the metric system is used in aviation (whereby in Russia altitudes above the transition level are given in feet)[120][121]. Sailplanes use the metric system in many European countries.
Accidents and incidents
Confusion over units during the process of metrication can sometimes lead to accidents. One of the most notable examples was during metrication in Canada. In 1983, an Air Canada Boeing 767, nicknamed the "Gimli Glider" following the incident, ran out of fuel in midflight.  The incident was caused, in a large part, by the confusion over the conversion between litres, kilograms, and pounds, resulting in the aircraft receiving 22,300pounds of fuel instead of the required 22,300kg.[122]
While not strictly an example of national metrication, the use of two different systems was a contributing factor in the loss of the Mars Climate Orbiter in 1999.  The National Aeronautics and Space Administration (NASA) specified metric units in the contract.  NASA and other organisations worked in metric units, but one subcontractor, Lockheed Martin, provided thruster performance data to the team in pound force-seconds instead of newton-seconds.  The spacecraft was intended to orbit Mars at about 150 kilometres (93mi) in altitude, but the incorrect data meant that it descended to about 57 kilometres (35mi).  As a result, it burned up in the Martian atmosphere.[123]
On 25 September 2009, the British Department for Transport published a draft version of legislation to amend its road signs legislation[124] for comment.  Among the proposed changes was an amendment to existing legislation to make dual-unit height and width warning and restriction signs mandatory.  This was justified in Paragraph 53 of the Impact Analysis[125] by the text "... Based on records from Network Rail's incident logs since April 2008, approximately 10 to 12 percent of bridge strikes involved foreign lorries. This is disproportionately high in terms of the number of foreign lorries on the road network."  This proposal was shelved with the change of government in 2010, though many bridges are now signed both ways.  The latest signage guidance consultation has proposed this once again.
See also

Anti-metrication
Change management, a field studying how changes can be efficiently implemented in modern communities
Conversion of units
Language reform
Metric clothes sizes (EN 13402)
French units of measurement
Metrication in Chile
Metrication in the United Kingdom
Metrication in the United States
Metrication in Canada
Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States
Preferred numbers
Spread of the Latin script

When was the metric system adopted by Europe?


The Antarctic bottom water (AABW) is a type of water mass in the Southern Ocean surrounding Antarctica with temperatures ranging from −0.8 to 2°C (35°F), salinities from 34.6 to 34.7psu. Being the densest water mass of the oceans, AABW is found to occupy the depth range below 4000m of all ocean basins that have a connection to the Southern Ocean at that level.[1]
The major significance of Antarctic bottom water is that it is the coldest bottom water, giving it a significant influence on the movement of the world's oceans. Antarctic bottom water also has a high oxygen content relative to the rest of the oceans' deep waters. This is due to the oxidation of deteriorating organic content in the rest of the deep oceans.  Antarctic bottom water has thus been considered the ventilation of the deep ocean.
Formation and circulation
Antarctic bottom water is created in part due to the major overturning of ocean water.
Antarctic bottom water is formed in the Weddell and Ross Seas, off the Adélie Coast and by Cape Darnley from surface water cooling in polynyas and below the ice shelf.[2] A unique feature of Antarctic bottom water is the cold surface wind blowing off the Antarctic continent.[3] The surface wind creates the polynyas which opens up the water surface to more wind. This Antarctic wind is stronger during the winter months and thus the Antarctic bottom water formation is more pronounced during the Antarctic winter season. Surface water is enriched in salt from sea ice formation. Due to its increased density, it flows down the Antarctic continental margin and continues north along the bottom. It is the densest water in the free ocean, and underlies other bottom and intermediate waters throughout most of the southern hemisphere.  The Weddell Sea Bottom Water is the densest component of the Antarctic bottom water.
Evidence indicates that Antarctic bottom water production through the Holocene (last 10,000years) is not in a steady-state condition,[4] that is to say that bottom water production sites shift along the Antarctic margin over decade to century timescales as conditions for the existence of polynyas change.  For example, the calving of the Mertz Glacier, which occurred on 12–13 February 2010, dramatically changed the environment for producing bottom water, reducing export by up to 23% in the region of Adelie Land.[5]  Evidence from sediment cores, containing layers of cross-bedded sediments indicating phases of stronger bottom currents, collected on the Mac.Robertson shelf [6] and Adélie Land[7] suggests that they have switched "on" and "off" again as important bottom water production sites over the last several thousand years.

Atlantic Ocean
The Vema Channel, a deep trough in the Rio Grande Rise of the South Atlantic at , is an important conduit for Antarctic Bottom Water and Weddell Sea Bottom Water migrating north.[8] Upon reaching the equator, about one-third of the northward flowing Antarctic bottom water enters the Guiana Basin, mainly through the southern half of the Equatorial Channel at 35°W. The other part recirculates and some of it flows through the Romanche Fracture Zone into the eastern Atlantic.[9]
In the Guiana Basin, west of 40°W, the sloping topography and the strong, eastward flowing deep western boundary current might prevent the Antarctic bottom water from flowing west: thus it has to turn north at the eastern slope of the Ceará Rise. At 44°W, north of the Ceará Rise, Antarctic bottom water flows west in the interior of the basin. A large fraction of the Antarctic bottom water enters the eastern Atlantic through the Vema Fracture Zone.[9]

Indian Ocean
In the Indian Ocean the Crozet-Kerguelen Gap allows Antarctic bottom water to move toward the equator. This northward movement amounts to 2.5Sv. It takes the Antarctic Bottom Water 23 years to reach the Crozet-Kerguelen Gap.[10]  South of Africa, Antarctic bottom water flow northwards through the Agulhas Basin and then east through the Agulhas Passage and over the southern margins of the Agulhas Plateau from where it is transported to into the Mozambique Basin.[11]

Steele, John H., Steve A. Thorpe and Karl K. Turekian, editors, Ocean Currents: A derivative of the Encyclopedia of Ocean Sciences, Academic Press, 1st ed., 2010 ISBN978-0-08-096486-7
Seabrooke, James M., Hufford, Gary L., and Elder, Robert B., “Formation of Antarctic Bottom Water in the Weddell Sea,” Journal of Geophysical Research, Vol. 76, No. 9, pp.2164–2178, 1971
Fahrbach, E., G. Rohardt, N. Scheele, M. Schroder, V. Strass, and A. Wisotzki, “Formation and discharge of deep and bottom water in the northwestern Weddell Sea”, Journal of Maritime Research, 53(4), pp.515–538, 1995


The List of Florida hurricanes encompasses approximately 500tropical or subtropical cyclones that affected the state of Florida. More storms hit Florida than any other U.S. state,[1] and since 1851 only eighteen hurricane seasons passed without a known storm impacting the state. Collectively, cyclones that hit the region have resulted in over 10,000 deaths, most of which occurring prior to the start of Hurricane Hunters flights in 1943. Additionally, the cumulative impact from the storms totaled over US$191billion in damage (2017dollars), primarily from Hurricane Andrew, Hurricane Irma and hurricanes in the 2004 and 2005 seasons.
Climatology

Tropical cyclones have affected Florida in every month of the year with the exceptions of January and March. Nearly one-third of the cyclones affected the state in September, and nearly three-fourths of the storms affected the state between August and October, which coincides with the peak of the hurricane season. Portions of the coastline have the lowest return period, or the frequency at which a certain intensity or category of hurricane can be expected within 86mi (139km) of a given location, in the country. Monroe County was struck by 26 hurricanes since 1926, which is the greatest total for any county in the United States.[4]
In a Monthly Weather Review paper published in 1934, the U.S. Weather Bureau recognized Key West and Pensacola as the most hurricane-prone cities in the state; Key West experiences both storms developing from the western Atlantic Ocean and the Caribbean Sea, while Pensacola has received hurricanes crossing the state as well as storms recurving in the northern Gulf of Mexico.[5] The earliest storm to affect the state was the 1952 Groundhog Day Tropical Storm, and the latest storm to impact the state was a hurricane making landfall on December1, 1925.
The strongest tropical cyclone to make landfall on the state was the Labor Day Hurricane of 1935, which crossed the Florida Keys with a pressure of 892mbar (hPa; 26.35inHg); it is also the strongest hurricane on record to strike the United States. Out of the ten most intense landfalling United States hurricanes, four struck Florida at peak strength.[2]
Lazaro Gamio of the Washington Post created a series of maps depicting the paths of all hurricanes to impact Florida from 1916 to 2015.[6]
Pre-1900

The first recorded tropical cyclone to affect the area that is now the state of Florida occurred in 1523, when two ships and their crews were lost along the western coastline.[7] A total 159 hurricanes are known to have affected the state prior to 1900, which collectively resulted in at least 6,504 fatalities and monetary damage of over $102million (2017dollars). Additionally, at least 109 boats or ships were either driven ashore, wrecked, or damaged due to the storms. A strong hurricane struck northwest Florida on May 28, 1863, and is the earliest landfall during the year known in the US.[8]
Information is sparse for earlier years due to limitations in tropical cyclone observation, though as coastlines became more populated, more data became available. The National Hurricane Center recognizes the uncertainty in both the death tolls and the dates of the events.[9]

1900–1949

In the period between 1900 and 1949, 108 tropical cyclones affected the state, which collectively resulted in about $4.5billion (2017dollars) in damage. Additionally, tropical cyclones in Florida were directly responsible for about 3,500 fatalities during the period, most of which from the 1928 Okeechobee Hurricane. The 1947 season was the year with the most tropical cyclones affecting the state, with a total of 6 systems. The 1905, 1908, 1913, 1927, 1931, 1942, and 1943 seasons were the only years during the period in which a storm did not affect the state.
The strongest hurricane to hit the state during the period was the Labor Day Hurricane of 1935, which is the strongest hurricane on record to strike the United States.[10] Several other major hurricanes struck the state during the period, including the 1926 Miami Hurricane, the 1928 Okeechobee Hurricane, and a cyclone each in 1945 and 1949 which made landfall as a Category 4 hurricane.
1950–1974

In the period between 1950 and 1974, 85 tropical or subtropical cyclones impacted the state, which collectively resulted in about $7billion (2017dollars) in damage, primarily from Hurricanes Donna and Dora. Additionally, the storms were directly responsible for 93 fatalities and indirectly for 23 more deaths. Several tropical cyclones produced over 20inches (500mm) of rainfall in the state, including Hurricane Easy, which is the highest total during the period. The 1969 season was the year with the most tropical cyclones affecting the state, with a total of 8 systems. The 1954 and 1967 seasons were the only years during the period in which a storm did not affect the state.
The strongest hurricane to hit the state during the period was Hurricane Donna, which was the 8th strongest hurricane on record to strike the United States.[10] Additionally, Hurricanes Easy, King, Cleo, Isbell, and Betsy hit the state as major hurricanes.

1975–1999

In the period between 1975 and 1999, 83 tropical or subtropical cyclones affected the state, which collectively resulted in $51.1billion (2017dollars) in damage, primarily from Hurricane Andrew, and 54 direct casualties. The 1985 season was the year with the most tropical cyclones affecting the state, with a total of 8 systems. Every year included at least 1 tropical cyclone affecting the state. The strongest hurricane to hit the state during the period was Hurricane Andrew, which was one of only three Category 5 hurricanes to strike the United States. Andrew, at the time, was the costliest tropical cyclone in United States history and remains the sixth-costliest. Additionally, Hurricanes Eloise,  David, and Opal hit the state as major hurricanes.

2000–present

The period from 2000 to the present was marked by several devastating North Atlantic hurricanes; as of 2017, 79 tropical or subtropical cyclones have affected the U.S. state of Florida. Collectively, cyclones in Florida over that period resulted in over $123 billion in damage, most of it from Hurricane Irma.[11] Additionally, tropical cyclones in Florida were responsible for 145 direct fatalities and at least 92 indirect ones during the period. Eight cyclones affected the state in both 2004 and 2005, which were the years with the most tropical cyclones impacting the state. Every year included at least one tropical cyclone affecting the state.
The strongest hurricane to hit the state during the period was Michael, which was the strongest hurricane to strike the United States since Hurricane Andrew. Additionally, hurricanes Charley, Ivan, Jeanne, Dennis, Wilma, Irma, and Michael made landfall on the state as major hurricanes.

Florida major hurricanes
The following major hurricanes either made landfall on the state as a major hurricane or brought winds of Category 3 status to the state. For storms that made landfall twice or more, the maximum sustained wind speed, and hence the highest Saffir-Simpson category, at the strongest landfall is listed. Only the landfalls at major hurricane intensity are listed. A * indicates that the storm made landfall outside Florida, but brought winds of major hurricane intensity to part of the state. Storms are listed since 1851, which is the official start of the Atlantic hurricane database.[2][3] Originally, hurricanes were classified by central pressure in the 20th century;[3][12] however, modern practices quantify storm intensities by maximum sustained winds.[13] United States hurricanes are still classified by central pressure from 1921–1979;[3][12] therefore, the maximum sustained winds in the Atlantic hurricane database (HURDAT) are utilized for storms from 1921–1979,[2] since this period has not been reanalyzed by the Atlantic hurricane reanalysis project.[14]

Monthly statistics

Number of recorded major hurricanes affecting FloridaMonthNumber of major hurricanesJuly1August5September19October10
Hurricane Fredrick Sept 12th 1979
Deadliest storms
The following is a list of hurricanes with 100 or more deaths in the state.

See also

Atlantic hurricane
Climate of Florida
List of Atlantic hurricane seasons
List of Atlantic hurricanes
List of wettest known tropical cyclones in Florida
Tropical cyclone

Further reading

What is the deadliest hurricane in Florida's history?