Play With (Part of a) Universe in Your Computer

Universe Sandbox
Created by Dan Dixon

"An Interactive Space Simulator
"Download Now!

"Smash planets together, introduce rogue stars, and build new worlds from spinning discs of debris. Fire a moon into a planet or destroy everything you've created with a super massive black hole.

"You can simulate and interact with:

• Our solar system: the 8 planets,160+ moons, and hundereds[!] of asteroids
• Nearest 1000 stars to our Sun
• Our local group of galaxies
• An unlimited number of fictional scenarios

"Tinker with your creation or sit back and watch the effects of gravity unfold. It's fun, accessible, and easy to use."

The first 60 minutes are free.

I have not tested this, or researched the software - but it sounds intriguing. I'd appreciate a comment from anyone who has used Universe Sandbox.

Cool 2D Vector Simulation

"Flash Physics Engine Box2DFlashAS3 1.4.2" is a two-dimensional physics simulator: Have fun, moving the objects. You can even toss them.