Last month I shared Distance to Mars a cool, although slow, visualization of the vast distance between us and our nearest neighbor. Even slower, Josh Worth's visualization is a side scrolling parallax site site using a linear ruler at the bottom of the screen as a literal scale. If the Moon Were Only One Pixel: A Tediously Accurate Model of the Solar System is a well designed and elegant experience made with HTML5. I confess, I skipped around a bit ;)
