I've been reading these boards for a while, and I just had a few questions about the Asteroid Belt I couldn't find answers to with the search engine.
1) How many asteroids are there? And how small are they?
2) Given that, what is the average density of them? Is it possible to send a spacecraft through them without encountering any objects?
3) How big is the total mass of all the asteroids? Is it possible to ever find out an accurate figure for this?
4) What is the accepted for theory for how the belt formed? Remnants of the Solar System formation or destroyed planet?
Links to good websites on this subject would also be helpful, the first search I did showed something about exploding planets, so I figured asking here would get me a more authoritative answer.