Unsolved
The so-called perfect hollow metal ball mainly means that the shell is integrally formed, has no pores, uniform thickness, no impurities in the ball, and it does not matter whether it is vacuum or not. Can such a ball be made with current technology? How to make it?
I have two thoughts: First, can the self-growth of metals be realized at present? The second is the existing mold, like a chocolate ball, brush a layer of molten metal on it, and the mold will automatically break at a certain time. But how to ensure that the thickness of the shell is uniform and how to remove the mold impurities in the ball?
