A vector is a mathematical construct that has magnitude and direction. The cross product of two vectors is a binary operation in three-dimensional space that results in a third vector that is ...
In the present situation, both Earth and Mars are moving in the same direction around the Sun, but the slower one, Mars, appears to move backwards compared to the faster one, Earth. Just an illusion. The retrograde motion of Mars â like the apparent motion of the slower car on the highway â is nothing more than an illusion.
Sometimes the planets appear to change direction in the sky. This retrograde motion is entirely an illusion caused by the Earth passing the slower moving outer planets. Sometimes, the planets seem to move backwards!Typically, the planets shift slightly eastward from night to night, drifting slowly against the backdrop of stars. From time to time, however, they change direction.ometimes the planets appear to change direction in the sky. This retrograde motion is entirely an illusion caused by the Earth passing the slower moving outer planets. Sometimes, the planets seem to move backwards!