system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How does Thermal Imaging work?
gpt
Heat sources emit electromagnetic radiation with a frequency respecting to their temperature. The visible spectrum of EM radiation ranges from red to violet. The sun's surface is about 5000 Kelvin hot and our eyes happen to see this light. Infrared means that the frequency of the EM radiation coming from an object is below the visible specrum due to lower temperature than the sun, anyway it can still be detected and it's frequency measured pretty accurately.

But How do we get a picture we CAN see?

Like digital cameras have light sensitive chips that render visible light directly to true red- green- and blue information in their memory, we can build a chip that detects light of lower frequency and renders it to any other colour and intensity value in real time.

It's just a microchip doing real time calculus, mapping the gathered frequency and intensity information to another color map we can display and see.