The thing that's interesting is that Celestia accurately models the
distance between celestial bodies, and you can simulate a "trip" like
from Earth to Mars in real or accelerated time; at a speed of your
choosing. Even moving at light speed will often take incredible,
exhaustive amounts of real time to get to a destination using
"Travel"...which is a bit instructive, I think.
The fastest way to move about is to use "Go To Object" in the Location
menu - just open that dialog and type in the name of a planet or body
you wish to move to - like Jupiter, Saturn, Alpha Centauri, etc. Then
use your scroll wheel to zoom in/out, or put a number in Distance; with
is an "elevation" from/above the body (I like to use the Radii option).
If you leave the default Distance number for Earth you'll end up below
the surface of a larger body like Jupiter and you need to pull back a
bit to see it - that's why I like to shift it to Radii. Your location
above the body will be geostationary, and if you accelerate time you can
observe sun shadow over the surface as objects move in relation to one
another.
It's pretty intuitive, the more you play with it the more you'll pick
up. I'm very surprised with the graphics and ability to add
objects...tons of free objects to add and play with here:
http://www.celestiamotherlode.net/
It's a *very* powerful simulation for a freebie. Can keep a space-geek
amused for light-years...happy travels.
Here's another free one - lunar rover for Mac and PC:
http://www.frassanito.com/RoverSIM/
I haven't fooled around with this one, but thought it worth a bookmark...
--
- Rufus