Shouldn’t time and usage make things more broken, less smooth?
In: Physics
Sometimes use makes things less smooth, and sometimes it makes them more. Depends on the material being worn, and the material doing the abrasion.
“Smooth” is essentially the amount of imperfections on the surface of a material. More specifically, the *differences* between the imperfections. You can think of the unit of measurement as microns, as that’s what polishing compounds are measured by. So a 2 micron polishing compound on a very fine sharpening stone will result in a razor sharp edge.
So an object like sandpaper is not smooth, because it has massive irregularities from one portion of the surface to the other. Glass, on the other hand, has irregularities in it’s surface with very little difference in hight between them. If you were to look at the mirrors in the telescopes used by NASA, you’d fine they are at the limits of human ability to make things “smooth”. In fact, were those space mirrors magically blown up to the size of the whole planet, the difference in the highest point versus the lowest point would be a gentle hill. That sandpaper could have differences equivalent to the Marianas Trench and Mount Everest.
What about surfaces like wood, that are soft, and easily damaged, you may ask. Well, if that wood is on a table that gets hit by forks and knives, plates, and glasses, you’re going to *lose* a smooth finish. If that wood is on a handrail that only gets worn down by soft human touch, you’ll gain smoothness. All because of the differences between the imperfections on each of those items.
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