system
Given the following post, respond as if you're commenting on Reddit:
human
What causes the blur that we see over hot surfaces?

I was wondering what that distortion or blur is that we see above things that get really hot, but have no open flame.
gpt
The object heats the air around the object and causes convection currents in the air.  This causes fluctuations in the density of the air (hot air is less dense than cool air).  The density fluctuations cause light rays traveling through the affected region of air to bend due to refraction.  The refraction distorts shapes.  Some of the blurriness is due to refraction itself and some of it is due to the fact that air density fluctuates from one spot to another and over time, creating slightly different images (not unlike the twinkling of stars when seen through the atmosphere).