system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why Are There "Dead Spots" On Paper When Attempting To Write With Ballpoint Pen?
gpt
Ball point pens work by rolling a ball on a surface.   This requires the surface have significant friction.   Ball point pens don't work on glass.

Paper at microscopic level isn't smooth.  It s matted weave of fibers.  Like a wool sweater. But if you iron a sweater flat, it won't be fluffy and soft and have friction.