system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Non-Euclidean Geometry

I don't know where to begin. What is it? How does it work? Is it a thing in real life?
gpt
Draw a triangle on a globe. Measure its angles. They don't add up to 180.  
That is non-euclidean geometry, right there before your eyes.  
Useful for many things, including, how do we get this plane from San Francisco to Tokyo the fastest? Answer: go over Alaska.