I am an accomplished welder by trade. I can weld in any position. Imagine changing the molecular structure of a cold piece of steel to a molten mass of metal and then having to move fast enough in order to run the perfect weld pass fighting the forces of gravity that want to pull the molten mass towards the center of the Earth. Not very remarkable. But what is remarkable is when the arc is struck and in that instant the Big Bang occurs where the weld is as hot as sun of the layers of the sun. There is also what is called spatter or interactions with the weld that cause hundreds of small metalic sphere shaped balls if molten metal to be rejected from the center of the world. Sometimes the spatter sticks to the metal but it is always spherical, like the core of Moon. I think it would be interesting to video someone welding and watch the process in slow motion to see what causes the molten spheres to become solid spherical shapes resembling the core of an object like the Moon.