system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do heat seeking missiles seek heat?
gpt
Infra red sensors.

Have you ever seen thermal imaging goggles? All objects that have warmth radiate in the infra red.

If you are hotter than your surroundings you glow in the infra red spectrum.

Engines, turbine exhaust, etc. Are all quite hot and therefore to infra red sensors seem bright, like light sources.