The purpose of this series is to explore and attempt to render the Doppler effect in a two or more body system.  The Doppler effect describes the change in color as a light-emitting object moves through space.  That is to say, as an object moves closer to the viewer, the successive light waves are emitted more closely together, resulting in a blueshift.  Conversely, as the object moves away, the waves are emitted farther apart, and so the light appears redder.  The Doppler effect can also be applied to sound but that is not relevant to this project.

	The images we create will consist of two major objects: a central blackbody and an orbiting, light-emitting object.  The central body, centered on the left of the image, serves as a backdrop for a series of geometric shapes that change size and color depending on the color of the orbiting object.  The orbiting object describes a parabolic path starting from the upper left of the image and moving to the lower left, and changes size and color as it changes position.  The shapes on the central body and the color of the orbiting object complement each other against a background that shifts between various shades of grey to create an interesting contrast.  

	This procedure predominately uses modulo to convert n into a specific number that will be used to transform the different objects at play in the image, as well as reference items in different lists that affect color, for instance with (list-ref (mod n 11) doppler-color-tree).  This call will alter the orbiting object through a list of 11 preset colors ranging from bright red to bright blue.  The orbiting object and the central object are both drawings that are converted into an image.  The shapes imposed over the central object are drawn using turtles (well, a single turtle), and consist of twenty-five hexagons (at least) rotated about the center of the central object that vary in size with n.  Since the drawings form the base of the image, a second orbiting object was created using image-select-ellipse! to simulate depth of focus.  Against a dark background, it is quite effective.

	We guarantee over 1000 original images by our extensive use of modulo: the size and position of the orbiting object change thirteen times, and rotate through eleven colors as mentioned, producing one hundred and forty-three combinations.  There are at least seven permutations of the shapes on the central object, which each cycle through the color complements of the orbiting object, allowing for well over 1001 unique images.