I found this article on Popular Mechanics, so you know they know what they are talking about, but it is very interesting and really drives home how far off we are from a lot of very popular syfy concepts and ideas.
The article basically outlines the insurmountable effort that it would take humanity to construct a world or a Death Star like planet.
This is an interesting article because it puts some real number behind how much material and time it would take to build a Death Star. Not only that but it also puts into aspect the physics of creating something like that. Such as the way the floors would have to be designed, basically upside down. To create gravity the planet would need to spin, this act alone would create an artificial gravity. The center of the constructed planet would have no gravity, but it would get stronger as you journeyed from the center out. The farthest floors from the center would have the strongest gravity because of the spin.
The article also talks about creating an actual rocky planet by collecting molecules. To me this process seems way too complicated, also I will confess that I did not truly understand it. The article talks about pulling molecules from near the sun and to keep compressing them to create heavier elements. The problem with this is that this process would generate an enormous amount of heat, comparable to the surface of the sun. So it would take thousands of years for the newly constructed planet to cool and be available as a place of residence. Why not go gather tons of asteroids and lump them together, that seems far simpler to me, but what do I know.
It really is eye opening of the daunting task that it would take to create something like this. When it is broken down it really make one wonder if humanity will ever reach that stage when this will even be possible. As the end of the article states “it is best to leave planet building to nature…”