http://tierneylab.blogs.nytimes.com/2009/09/11/the-beautiful-universe-astronomy-quiz/?apage=2#comments I defer to the other posts for the extra credit answers but suggest an old idea for the model Milky Way. Most of us remember the classic film POWERS OF TEN, put out by Charles and Ray Eames back in 1977 ( http://powersof10.com/ ). I would re-hash this idea by creating a Powers of Ten museum, consisting of a series of cubical rooms, each filled with models of things at that scale. In the portal from one room to the next, you could have a miniature model of the previous room to show how much bigger this room is than the previous one. Of course, there would have to be a wing where everything got smaller as well. I envision the layout as a spiral, with the option to go smaller (down) or bigger (up) at ground level, and an elevator with a brief video as you zoom back to human scale. I think seeing the gradual shift in size and having to take the time to walk through the exhibit would help the public process the vastness of space better than a logarithmic scale. As I said, it is an old idea, re-hashed, but sometimes you just can't improve on a classic. -- SoSaysSunny