I don't have a complete grasp of all the code (maths has never been my strong point), but I managed to reverse engineer Thanassis's code to understand what I needed to change to 'downsize' the universe so it could be rendered within the Minecraft world.
The original code throws 30 random planets around a large sun and lets gravity do its job, usual a good percentage of the planets get drawn into the sun or collide with each other, those that don't usually end up in elliptical orbits around the sun.
This was a bit hardcore for the Pi to cope with rendering in Minecraft, so I simplified the code to initially create 3 planets that would sit in stable orbits; I then introduced a rouge planet into the system which throws everything out and the whole system is destroyed in a few cycles when the planets collide and eventually all fall into the sun.
Its really easy to change the planets in the simulation, just head to the line in the code which is headed with a comment #CREATE THE PLANETS HERE, and add as many as you want, giving them a position (x,y) and a velocity (x,y).
Download and run
You can download the code direct from git-hub, so run minecraft, open/create a world and follow the instructions:
If you want to have a go yourself:
Create a directory for the program
Copy the python api class library from minecraft to the programs directory
Create minecraft-planets.py python program
or open Idle and save minecraft-planets.py to the minecraft-planets directory