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  2. 50 metres - Wikipedia

    en.wikipedia.org/wiki/50_metres

    50 metres. 50 metres, or 50-meter dash, is a sprint event in track and field. It is a relatively uncommon non-championship event for indoor track and field, normally dominated by the best outdoor 100 metres runners. At outdoor athletics competitions it is used in the Special Olympics and a rare distance, at least for senior athletes.

  3. Metre - Wikipedia

    en.wikipedia.org/wiki/Metre

    The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre 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, where the second is defined by a hyperfine transition frequency of caesium.

  4. History of the metre - Wikipedia

    en.wikipedia.org/wiki/History_of_the_metre

    The frequency of the light from the methane-stabilised laser was found to be 88.376 181 627(50) THz. [ 185 ] [ 187 ] Independent measurements of frequency and wavelength are, in effect, a measurement of the speed of light ( c = fλ ), and the results from the methane-stabilised laser gave the value for the speed of light with an uncertainty ...

  5. Earth's circumference - Wikipedia

    en.wikipedia.org/wiki/Earth's_circumference

    t. e. Earth's circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi). [1] Measurement of Earth's circumference has been important to navigation since ancient times. The first known scientific measurement ...

  6. Sprint (running) - Wikipedia

    en.wikipedia.org/wiki/Sprint_(running)

    The world record in the 100-meter dash in 1924 was 10.4 seconds, while in 1948, (the first use of starting blocks) was 10.2 seconds, and was 10.1 seconds in 1956. The constant drive for faster athletes with better technology has brought man from 10.4 seconds to 9.58 seconds in less than 100 years.

  7. Kármán line - Wikipedia

    en.wikipedia.org/wiki/Kármán_line

    The U.S. Armed Forces definition of an astronaut is a person who has flown higher than 50 miles (80 km) above mean sea level, approximately the line between the mesosphere and the thermosphere. NASA formerly used the FAI's 100-kilometre (62-mile) figure, though this was changed in 2005 to eliminate any inconsistency between military personnel ...

  8. Orders of magnitude (length) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(length)

    The centimetre (SI symbol: cm) is a unit of length in the metric system equal to 10−2 metres (⁠ 1 100 ⁠ m = 0.01 m). To help compare different orders of magnitude, this section lists lengths between 10 −2 m and 10 −1 m (1 cm and 1 dm). 1 cm – 10 millimetres. 1 cm – 0.39 inches. 1 cm – edge of a square of area 1 cm 2.

  9. Height above mean sea level - Wikipedia

    en.wikipedia.org/wiki/Height_above_mean_sea_level

    Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods.