Metre m
About the Metre
The metre is the length of the path travelled by light in vacuum in 1/299,792,458 of a second. It was first defined by the French in 1791 as one ten-millionth of the distance from the equator to the North Pole, then embodied in the 1799 metre des archives and the 1889 platinum-iridium prototype. A krypton-86 wavelength definition followed in 1960 before the speed-of-light definition of 1983.
Related Units
Ångström
Å1 Å = 10⁻¹⁰ m = 0.1 nm (exact)
The ångström equals one ten-billionth of a metre, roughly the size of an atom. It is named after the Swedish physicist...
Inch
in25.4 mm (exact)
The inch is defined as exactly 25.4 millimetres. Britain and the United States agreed this value in the 1959...
Foot
ft0.3048 m (exact)
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Yard
yd0.9144 m (exact)
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