International Standard of Length
History of standards, modern definitions
“The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.” (adopted 1983)
History:
- “The meter was intended to equal 10-7 or one ten-millionth of the length of the meridian through Paris from pole to the equator. However, the first prototype was short by 0.2 millimeters because researchers miscalculated the flattening of the earth due to its rotation. Still this length became the standard. …. In 1889, a new international prototype was made of an alloy of platinum with 10 percent iridium, to within 0.0001, that was to be measured at the melting point of ice. In 1927, the meter was more precisely defined as the distance, at 0°, between the axes of the two central lines marked on the bar of platinum-iridium kept at the International Bureau of Weights and Measures (BIPM, Bureau International des Poids et Mesures) located outside Paris …..
What is a second? – More later.