When we observe the sky, we expect most objects to appear to move in a particular direction with the passing of time. The apparent motion of most bodies in the sky is from east to west. However it is possible to observe a body moving west to east, such as an artificial satellite or space shuttle that is orbiting eastward. This orbit is considered Retrograde Motion.
Når vi betragter himlen forventer vi at himmellegemerne bevæger sig i en bestemt retning over tid. Tilsyneladende bevæger himmellegemerne sig fra øst mod vest. Det er dog muligt at se f. eks. kunstige satellitter og rumskibe med en østgående bane, bevæge sig i modsat retning En sådan bane kaldes retrograd bevægelse.