system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can flies get in through windows, but it takes them a lot longer to get out through the same gap, or not at all?
gpt
There are many many flies on the outside, so it's likely that a small number of them will find your tiny window. The chance for each fly to find your window is very small. On the same note, the chance the fly will find the same small window out is still small. However, if you have things the fly is after such as food, it might also be choosing to stay because it "smells better" inside than outside.