... Astronomy Animations by Paul Francis is licensed under a Creative Commons Attribution 4.0 International License . ... Most of these animations were made using the excellent VPython programming language. ... The universe expanding at a constant rate. ... The universe expanding, but with such massive galaxies that eventually their gravity stops the expansion and causes the universe to recollapse. ... The VPython computer code used to generate the above simulations. ... VPython code used) . ...