system
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human
ELI5: Why do extremely hot items glow "red hot" as opposed to other colors, like green, blue, purple, etc.?

I was watching those recent videos on YouTube where a knife is heated until it's red hot and cuts into various objects...

I never considered it before, but I started to wonder why things turn red when they're extremely hot instead of other colors...
gpt
Heated objects produce light.

Even room-temperature objects are emitting light. It just isn't *much* light and the wavelength is way too long to see (it is low-energy).

The more an object heats up, then more energy it emits. It also starts to emit more energy of higher frequencies (higher energy levels). So if it gets hot enough, some of that light is now going to be in the visible spectrum, since it will be energetic enough to produce red light (but not much of a higher wavelength like green or blue light).

If you keep heating it, it will get yellower and yellower as more yellow light gets emitted (relative to the other energy it is emitting).

Eventually it does reach a point where it emitting enough higher energy light that it has a considerable amount of green or blue light being emitted. However, at this point, so much light is being emitted (and a lot of it is still red light) that the object will just appear white to us.