SpaceEngine - a free space simulation program that lets you explore the universe in three dimensions, from planet Earth to the most distant galaxies. Areas of the known universe are represented using actual astronomical data, while regions uncharted by astronomy are generated procedurally. Millions of galaxies, trillions of stars, countless planets - all available for exploration. You can land any planet, moon or asteroid and watch alien landscapes and celestial phenomena. You can even pilot starships and atmospheric shuttles.
Definitely the best space simulator out there so far. It's good enough already as it is. However, inclusion of time travelling capabilities would definitely be great including the ability to see the early universe by reversing time as well as the fate of the universe by fast forwarding it. Keep up the good work!