What is Mercury Retrograde? Three, and sometimes four, times a year, the planet Mercury appears to be moving backwards in the sky for a period of approximately 3 weeks. “Appears” is the key word here, because, technically speaking, no planet actually moves backwards in their orbits around the Sun. In fact, they don’t even slow down. Retrograde-station-direct cycles are essentially illusions that result from our point of view from Earth, simply because the Earth is also orbiting the Sun at a different speed than the other planets.