Welding
A joining process in which metals or thermoplastics are partly melted so that the parts fuse together. The joint solidifies as one body with the base material, unlike fastening with screws or adhesives.
In space vacuum, two clean pieces of the same metal can fuse on contact without heat. On Earth, oxide films and grime block this bond; in vacuum, bare atoms meet directly and act as one solid. This is cold welding, so spacecraft parts need coatings or anodizing.
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