As I lay in the bath the other day, lazing, luxuriating, and pondering deep philosophical matters, a question came into my mind that has often puzzled me before. The hairs on my legs are soft, much, much softer than the sharpened steel of my razor. So how come the former blunts the latter? I asked a scientist friend – what? No, later. He wasn’t in the bath with me! – and this is what he came up with:
Consider what a solid actually consists of.
The razor blade has a carefully structured array of mainly iron atoms, the hairs have long chains of proteins which are in themselves rings and chains of mainly carbon atoms.
Most often the thin strip of iron atoms will neatly slice between proteins cutting the hairs in two, but you have a lot of hairs (we all do though men’s legs get male pattern baldness!) and every now and then the strip of iron atoms will hit a hair such that a chain of carbon atoms can lever a single iron atom, or maybe two or three out of place.
On average if a knife is 1000 times harder than the material that is being cut then 1000 times as much damage will be done to the surface as to the knife, but after you’ve used the knife 1000 times …
If this wasn’t true you could never cut gemstones with metal saws but people have been doing it for centuries!
I relayed this information to Consuela (my Tejana maid) and she muttered something to the effect that shaving my own legs was the nearest I actually came to physical work these days. She’ll have to go…