system
Given the following post, respond as if you're commenting on Reddit:
human
[Fullmetal Alchemist]When Edward creates his weapons, what exactly is he exchanging?

From my understanding, you have to give something to get something. An Alchemist cannot create something out of nothing. So what exactly is Edward exchanging when his spear materialises from the ground.
gpt
Arm sword: Plating on his arm.

Anything from the ground: Iron and such is drawn from surrounding areas and concentrated to where the weapon is created. He could also be exchanging the ground itself, 4.5 carbon (or silicon what ever suits him) for 1 iron. The ratio was calculated on atomic mass. The ratio in "reality" could be different but the principal is the same.