Well it's because it depends on the microscopic surface topography underneath the bottle as it slid.
这是因为它取决于瓶子滑动时下方的微观表面形貌。
英语百科
Surface finish
Surface finish, also known a surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness. It comprises the small local deviations of a surface from the perfectly flat ideal (a true plane).