system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why roads look like wet puddles when it is extremely hot outside?
gpt
This is an example of a mirage. The sun heats up the bitumen, and it creates a very thin layer of very hot air. That hot air is less dense than the air above it, and this acts as a lens, curving light that approaches from a shallow angle upwards. This looks a bit like how light reflects off of a still puddle.