system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does paper burn so easily when lit at its edge, but doesn't immediately burn up if exposed to fire in the middle of the sheet?
gpt
In tbe middle oftbe sheet its smothering itself. The flame wants to go up and use oxygen yet the paper is in the way. At the edge it has the paper fuel, oxygen all around, and nothing covering the top of it.