Way back in 2001 when the original confusion about the relation of a nanometer to the width of a human hair originally surfaced, reader David Neiman, was kind enough to send us a histogram of hair widths from his own locks (average fibre diameter 72.1 microns with a standard deviation of 24 microns and a coefficient of variation of 33.3% for the statistically minded). Of course hair colour and the part of the body the sample was taken from also influence the diameter.
Confusion still rages with a nanometer being 100,000 times smaller than a human hair (making a hair 100 microns in diameter) to 1,000 times smaller (1 micron).
Three years later we still await a scientifically valid analogy. May we suggest a slightly tighter definition, that a nanometer is one hundred million times smaller than a large potato (which would have to vary between 1cm and a one meter in diameter to provide the same statistical variation as the hair analogy). Perhaps not.