This is quite simple the earth and other planets were formed to be round as we see from distances and as we approach ground level they are flat with a skybox that is slightly round to give the appearance that its round but it is indeed flat. Also as you look into the horizon and beyond we see foliage buildings cars etc... with lower detailed models and as you go way away they cull out ie dissapear to save resources on our minds and the universes computer ram and rom. thanks jamesey... that is all...