system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why when I use a pen and it stops writing, I can go to another place on the paper and continue to write, but when I come back to the spot it stopped working at, it doesn't work?
gpt
Sometimes there's a tiny bit of grease on your paper, in an invisible layer. This grease (finger oil; french fry grease; maybe some dripped from a roller at the paper factory) stops your ball-point pen's ball from rolling, which stops the flow of ink.