Multiple choice general knowledge science & technology If two pieces of metal touch in space, they fall down become permanently stuck together split into different piecess None of the above Reveal answer Fill a bubble to check yourself B Correct answer Explanation This is a real phenomenon called 'cold welding' or 'contact welding'. In the vacuum of space, there's no oxide layer or air separating two clean metal surfaces, so metallic bonding can occur and the pieces permanently fuse together.