Which term describes movement that goes backward?

The term that describes movement going backward is retrograde motion. This concept is often used in astronomy to refer to the apparent backward motion of a planet as observed from another planet, particularly Earth. For example, retrograde motion describes how planets like Mars appear to move in the opposite direction across the sky at certain times due to the relative positions and speeds of the planets in their orbits.

In addition to its astronomical context, the term can also be applied more broadly to describe any movement that is backward or reverses direction. Understanding retrograde motion helps in various fields, including physics and astronomy, as it illustrates important concepts about motion and perspective.

The other options relate to different concepts. Reverse motion refers more generally to any backward movement but does not encompass the specific astronomical implications that retrograde motion does. An ephemeris is a table or data file providing the calculated positions of celestial objects over time. Elliptical refers to the shape of orbits, specifically the oval shape that planets follow around the sun and does not pertain to the notion of motion direction.