Last in my little mini-series on the images from my new banner is Nathan Sawaya's sculpture of the solar system. Nathan notes that he tried to put them in roughly relative scales, but he also notes that he's an artist, not a scientist. For a great side-by-side comparison tool, go to this link, that lets you compare the various planets to each other. Nathan also insists on including Pluto atop his sculpture. Seven years ago there was a debate in the International Astronomical Union about the status of Pluto. It turns out there are at least four other similarly-sized rocks out there (and Eris is bigger than Pluto). Rather than have a constantly expanding solar system as further celestial bodies are discovered, the IAU came up with classifications of 'planet' (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), and 'dwarf planet' (Pluto and friends). Due to tradition, and quite possibly due to the connection with the Disney cartoon dog, many have resisted the reclassification of Pluto (for instance, it was a subplot of an episode of the sitcom Sports Night).