Many other systems for measuring length have been developed over the years, but the advantages of the French system have caused it to prevail in almost all coun- tries and in scientific circles everywhere. As recently as 1960, the length of the meter was defined as the distance between two lines on a specific platinum–iridium bar stored under controlled conditions in France. This standard was abandoned for sev- eral reasons, a principal one being that the limited accuracy with which the separa- tion between the lines on the bar can be determined does not meet the current requirements of science and technology. In the 1960s and 1970s, the meter was de- fined as 1 650 763.73 wavelengths of orange-red light emitted from a krypton-86 lamp. However, in October 1983, the meter (m) was redefined as the distance traveled by light in vacuum during a time of 1/299 792 458 second. In effect