Corrected: June 22, 2014 at 10:00 PM MDT
Previous versions of this story said a platinum bar cast in the 19th century was what the world used as the official length of a meter. It was the first official standard for the length of the meter. There's another in effect today.
Corrected: June 22, 2014 at 10:00 PM MDT
Previous versions of this story said a platinum bar cast in the 19th century was what the world used as the official length of a meter. It was the first official standard for the length of the meter. There's another in effect today.