This is an interesting fact that I came across while reading on my job. Never knew this yet we use it everyday!
In the quest for a universal standard of length, the metre is defined as 1650763.73 multiply by the wavelength, in a vacuum, of the orange-red radiation of the isotope krypton 86. (Taken from “Metrology For Engineers, 4th Edition” by J. Galyer and C. Shotbolt.)
Chen Kee
