Many different units of length have been used around the world. The main units in modern use are U.S. customary units in the United States and the Metric system elsewhere. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.
The base unit in the International System of Units (SI) is the metre, defined as "the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second." It is approximately equal to 1.0936 yards. Other units are derived from the metre by adding prefixes from the table below:
In the sport of athletics, the four-minute mile is the act of completing the mile run (1,760 yards, or 1,609.344 metres) in less than four minutes. It was first achieved in 1954 by Roger Bannister in 3:59.4. The "four-minute barrier" has since been broken by many male athletes, and is now the standard of all male professional middle distance runners. In the last 50 years the mile record has been lowered by almost 17 seconds. Running a mile in four minutes translates to a speed of 15 miles per hour (24.14 km/h, or 2:29.13 per kilometer, or 14.91 seconds per 100 meters).
Breaking the four-minute barrier was first achieved on 6 May 1954, by Englishman Roger Bannister. Two months later, during the 1954 British Empire and Commonwealth Games hosted in Vancouver, B.C., two competing runners, Australia's John Landy and Bannister, ran the distance of one mile in under four minutes. The race's end is memorialised in a statue of the two (with Landy glancing over his shoulder, thus losing the race) placed in front of the Pacific National Exhibition entrance plaza.
Sir Roger Gilbert Bannister, CBE (born 23 March 1929) is an English former athlete best known for running the first mile in less than 4 minutes.
In the 1952 Olympics in Helsinki, Bannister set a British record in the 1500 metres, but did not win the medal he expected. This humiliation strengthened his resolve to be the first 4-minute miler.