system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did ancient civilizations make ovens so hot that they could melt metal without the kinds on materials we have today?

EDIT: Thank you to everyone for such an insightful conversation!
gpt
Making a really hot fire doesn't require modern technology. That's all you're doing when you're working with metals or building kilns to fire pottery - just making a really hot fire. It's perfectly easy to make a fire that's thousands of degrees with just wood or coal. All you need is some structure to contain the heat (brick, ceramic, stone...etc), fuel, and some way to blow oxygen to get the fire really hot and keep it hot. These are all things that require no modern technology whatsoever.