Celestia: Real-Time Space Simulation
A coworker tipped me off to this cool space simulation that allows for three-dimensional travel of the universe. From the website:
Unlike most planetarium software, Celestia doesn’t confine you to the surface of the Earth. You can travel throughout the solar system, to any of over 100,000 stars, or even beyond the galaxy. All travel in Celestia is seamless; the exponential zoom feature lets you explore space across a huge range of scales, from galaxy clusters down to spacecraft only a few meters across.
I’ll admit that I can’t even grasp everything that one can do with this. In my short travels, I got lost somewhere outside of the Milky Way, did a demo, checked out constellations, and tried unsuccessfully to find a comet to follow.
Celestia runs on Windows, Linux/Unix, and Mac OSX. Additionally, ambitious sorts can create their own scripts for customized tours.
(Word of warning: If you don’t have a great graphics card (less than 16 megs), you’ll want to download the low res version.)