Google Sky Planet Orbits
Digressing slightly from the real-sized planets, I figured there might be some mileage in creating diagrams showing orbital positions around the Sun to run alongside normal Google Sky planetary motion animations. This way you can see more clearly how positions relate to one another, giving some insight into why and when retrograde / prograde motion occurs.
What I’ve done is put together a simple animated chart of planet orbits, which synchronizes with the Planets in Motion animation in the Google Sky Layers [Edit 2008/1/10 – this layer is now called ‘Our Solar System’]. The file combines several independently moving screen overlays, one for each planet, and displays them in the same manner as an orrery, in the top left corner of the Google Earth window. To view it, open the file below, and turn on the ‘Planets in Motion’ Layer:
Planets in Orbit (Google Earth v4.2 Required)
Ideally the diagram would include accurate relative orbital distances. Unfortunately this isn’t possible without cramping the inner planets so closely together they become indistinguishable. A logarithmic distance scale might work better, maybe even splitting the chart into two: Inner and Outer Planets – I’ll have to investigate this further. There isn’t really a whole lot of room to work with up there in the corner of the screen. 🙂