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1.6 × 10 −5 quectometers (1.6 × 10 −35 meters) – the Planck length (Measures of distance shorter than this do not make physical sense, according to current theories of physics.) 1 qm – 1 quectometer, the smallest named subdivision of the meter in the SI base unit of length, one nonillionth of a meter.
The first group of metric units are those that are at present defined as units within the International System of Units (SI). In its most restrictive interpretation, this is what may be meant when the term metric unit is used. The unit one (1) is the unit of a quantity of dimension one. It is the neutral element of any system of units. [2]
The unit of time should be the second; the unit of length should be either the metre or a decimal multiple of it; and the unit of mass should be the gram or a decimal multiple of it. Metric systems have evolved since the 1790s, as science and technology have evolved, in providing a single universal measuring system.
United States customary units form a system of measurement units commonly used in the United States and most U.S. territories [1] since being standardized and adopted in 1832. [2] The United States customary system developed from English units that were in use in the British Empire before the U.S. became an independent country.
The basic unit of length in the imperial and U.S. customary systems is the yard, defined as exactly 0.9144 m by international treaty in 1959. [2] [10] Common imperial units and U.S. customary units of length include: [11] thou or mil (1 ⁄ 1000 of an inch) inch (25.4 mm) foot (12 inches, 0.3048 m) yard (3 feet, 0.9144 m)
The 10th CGPM in 1954 resolved to create an international system of units [31]: 41 and in 1960, the 11th CGPM adopted the International System of Units, abbreviated SI from the French name Le Système international d'unités, which included a specification for units of measurement. [5]: 110
For large scales, megametre, gigametre, and larger are rarely used. Instead, ad hoc non-metric units are used, such as the solar radius, astronomical units, light years, and parsecs; the astronomical unit is mentioned in the SI standards as an accepted non-SI unit. [citation needed]
List of humorous units of measurement; List of unusual units of measurement; List of obsolete units of measurement; List of measuring instruments; List of nautical units of measurement; List of scientific units named after people; List of international units; List of SI electromagnetism units