Every few months, I come across something on the web that completely blows my mind. This morning, a friend of mine sent me a link to Nikon's Universcale web app. It puts the entire universe into proportion, from the smallest particle to the largest measurements of space.
From the femtometer to the light year, Universcale spans 40 magnitudes of measurement into a single cosmic web app. It's really amazing when you zoom all the way out into stars and galaxies and realize that every time you go a magnitude higher, everything you saw before, from the flea to Mount Everest, is contained in this tiny little grid in the lower-left side of the screen. Of course, the Carl Sagan-should-be-narrating-this planetarium music helps.
If you have a few minutes and want to feel really, really small (or really, really large, or really, really disoriented), check out Universcale. It will eat up your afternoon and enlighten you as to the true size and scope of the cosmos. Not bad for a Flash app.