0.1mm is not very smooth. According to wikipedia, 150 grit sandpaper has average particle size of 90-100µm edit: of course there is vigorous internet commentar

0.1mm is not very smooth. According to wikipedia, 150 grit sandpaper has average particle size of 90-100µm edit: of course there is vigorous internet commentary about billiard ball smoothness compared to earth: https://possiblywrong.wordpress.com/2011/01/03/is-the-earth-like-a-billiard-ball-or-not/ https://possiblywrong.wordpress.com/2011/01/03/is-the-earth-... https://skeptics.stackexchange.com/questions/10763/is-earth-as-smooth-as-a-billiard-ball https://skeptics.stackexchange.com/questions/10763/is-earth-... https://billiards.colostate.edu/faq/ball/smooth/ https://billiards.colostate.edu/faq/ball/smooth/ Which mostly seem to agree that earth definitely is not as smooth as a (new) billiards ball, but there is lots of debate about the details.