system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 If two metals touch in space they fuse permanently. Why?

Is there any benefit welding in a vacuum on earth vs conventional welding?
gpt
Well metal is just a grid of atoms really with electrons flowing between them. When you touch two pieces together on earth there is still air between them which keeps them seperate even if its a tiny amount bonded to the outside of the metal.

In space however theres no air so when you touch two clean surfaces of metal together the atoms on the boundry have no idea that they are two seperate pieces anymore. They just bond together like the rest of the metal.