A P P A R E N T R E T R O G R A D E

 

Don’t tell me the moon is shining; show me the glint of light on broken glass
— Anton Chekhov


A P P A R E N T R E T R O G R A D E

Apparent retrograde motion is a phenomenon that results from observing a system from a fixed point within it. When one body orbits another in the direction opposite the rotation of the orbited body, it is said to be in retrograde, meaning “moving backward.” But this can appear to be the case when bodies are in supersynchronous orbit as well. In this case the orbit and rotation move in the same direction, but the rotation of the planet is faster than the orbit of its moon so that to the observer standing on the planet, the moon is perceived to be moving in the opposite direction. Such is the case for us. Our moon appears to travel the sky from east to west. In actuality, it is moving from west to east, but the Earth completes its rotation more quickly than Luna completes its orbit. The motion of our moon across the sky is observable and happens in a predictable pattern. Yet it is illusory, and mathematical analyes of astronomical data allow scientists to better model the situation. What I have tried to do in this series is use selections from my catalog of lunar photographs to create a sequence of images where what appears to be happening is often belied by the additional data provided.