system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does heat alter our perception and create a "wavy" effect.

For example, the area above a strong heater.
gpt
Heat changes the refractive index of air (due to expansion), and as currents and eddies of air pass through a heater – or over a desert – there's an uneven heating effect, causing slight but visible waves of differing refraction.