Edit made on September 30, 2025 by ColinWright at 17:08:54
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WW WM
HEADERS_END
Broadly speaking, the original definition of the metre was
|>> [[[
"one ten-millionth of the distance _
from the North Pole to the Equator _
on the meridian running through Paris."
]]] <<|
This was adopted in competition with the definition of
|>> [[[
"the pendulum length giving of a pendulum that _
has a half period of one second"
]]] <<|
The definitions are remarkably similar because of the coincidence that EQN:\pi^2 is very nearly equal to /g,/ acceleration due to gravity.
However, both definitions have problems. You can read more about them in the Wikipedia article quoted below.
More recently, the metre has been redefined as:
|>> [[[
"the distance travelled by light in vacuum during _
a time interval of 1/299 792 458 of a second."
]]] <<|
Thus the speed of light is now, by definition, 299 792 458 m/s.
----
Further reading:
* http://en.wikipedia.org/wiki/Metre