The model illustrates the concept of distance between space objects. Slides in the left-side window depict a variety of space objects (the North Star, the center of the Galaxy, Andromeda Nebula, a supercluster of galaxies, etc.) and the distance to them in light years. Corresponding slides in the right-side window display what happened on the Earth in the times when the light that is visible right now was radiated by the remote astronomical objects.
Use the scale at the bottom part of the model to go through the slides. You may also watch the slides in a continuous mode. Press "Run" button. Slides will alternate at a 3 second interval in a predetermined sequence, starting with the current one. "Stop" button suspends the animation. Press "Reset" button to return the model to the first slide.