## Most recent change of DefinitionOfTheMetre

Edit made on February 20, 2009 by RiderOfGiraffes at 11:41:52

Deleted text in red / Inserted text in green

WW
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 length of a pendulum with length giving _
a one second half the period" period of one second"
]]] <<|

The definitions are remarkably similar, but 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.

----