Celestia

"The free space simulation that lets you explore our universe in three dimensions. Celestia comes with a large catalog of stars, galaxies, planets, moons, asteroids, comets, and spacecraft. If that's not enough, you can download dozens of easy to install add-ons with more objects"

Celestia is a magnficant program introduced to me by my physics teacher when I was only in year 9 at school. As mentioned in the introduction it is a simulator of basically the entire known universe. Once you download the 13.9MB install file and run it, you'll be enjoying lightyears of astronomy.

Each planet, comet, moon and star is beautifully rendered. You can zoom down on Earth and see the different countries, complete with night/day renders. The night side of the Earth shows tiny little specks of light that you'd expect to see looking from space. If you want more detail, you can download new surface maps, to add more contour to the surface, or even city models and landmarks to view when zoomed in really close.

Movement in your "spaceship" can be a bit annoying at first, but people familiar with GoogleEarth shouldn't have too much problem. Hold right-click to rotate around the object, and scroll with the mouse to zoom in and out. By double-clicking an object you can focus your view on it. Doing this, you can leapfrog all across the universe. Free range movement is also possible.

All the while you are moving around, the planets, stars and galaxies themselves are moving in real time. You can speed up or slowdown time, even go back in time. If you want to find the MIR spacestation you'll have to go back in time to March 23, 2001, to when it actually still existed. There are many other spacecraft, each with their trajectory and paths mapped out prefectly. By typing in Cassini you can find the Cassini spacecraft at it's last known position (you may need to go back in time a bit, to when the program was last updated because the prgrammers only map out what's known to them) and trace it back to it's early flight and the amazing slingshots around the moon and jupiter.

As mentioned earlier, there are many addons you can download and install of Celestia, such as solar flare events of Sol, new spacecraft, and models of planets. There are also some sci-fi addons, like the Sulaco from the Alien films, the Asgard ship and Stargate ring from Stargate, even the Darth Vader's Deathstar if you really want.

These additons can be found here:
http://www.celestiamotherlode.net

Celestia is marked as basic through to advanced, as young children love to fly through the universe looking at the planets, even if they don't know what they are doing. The advanced rating is for the sheer power of this program. You can see apparant and absolute magnitude, diameter, type, and temperature of stars. You can determine distances between objects in the universe, and other features include constellation overlays in 3D, scripted fly-throughs of the universe, and a search feature to find any object you want.

http://www.shatters.net/celestia/

Level: Basic - Intermediate - Advanced