at the moment, i have 2 empty spheres, and a dome (repurposed to be full of dragons now) out there. i made a bunch of tiny "bubbles" when i was little. it never works properly if you attempt to "make rocks". that's why there are so many asteroids. derp derp. 

i will make another small sphere to show how. 

i do not think you can build a sphere on a computer...