Mercury orbiting our sun. The simulation begins with the planet Mercury (the nearest planet to the sun) appearing at its maximum distance from the sun (aphelion). As Mercury circles around, so ghostly echo planets follow to trace its course. Mercury speeds up as it approaches the sun. This is obvious in the movie and by the fact that the ghost planets stretch further apart in when closer to the sun. Once the movie has fully appeared you can move the slider back and forth to see these effects at different speeds.