Serious #question about #length #units: what distance do #journalists mean by "the thickness of a human #hair"? What's the convention?

If you're at all familiar with a human body, you'll be aware that the hairs on it come in many different thicknesses, and the ones on your head are probably too thin to judge anyway.

Please, in microns or some other recognised unit, what size are you on about when you say "a fifth of the width of a human hair"?

At least give the translation!!

#HumanHairUnit