Celestia

Celestia is a 3D simulator of the Solar System. It’s pretty amazing actually. You can move about, lock onto planets, land on their surface. _It’s not exactly limited to the solar system, more like _the Universe, _i.e. as much of it is known to mankind. You can even move out and visit other _galaxies, systems, e.t.c. 

It also has a _“TLC Feature 😀 ” _that enables you to speed up or slow down time, or even _stop it, or reverse it. _That;s not all, it has a lot of features and is definitely worth trying.

Installing it in Ubuntu is relatively easy, simply fire up a terminal(CTRL + Alt + T), and paste the following code:
sudo apt-get install celestia-gnome