How do Astronauts Weld in Space?

Shelby Rogers

On Earth, metals need to be heated past their melting points in order to weld together. But how does that work in space where there isn't oxygen to facilitate a flame?

This video from the minds at Veritasium explains the science of "cold welding." When two metals touch in space, they can fuse together without the need for an open flame. Why? Because metals have both positively moving ions in a "sea" of negatively moving electrons. Without oxygen in space, the oxide layer over the metals disappears. Just add a little bit of force and the metals can fuse together.