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.
The same thing happens as Earth passes the slower moving outer planets. When we pass Jupiter, for example, the gas giant appears to reverse course in the sky for a couple of months. A schematic of how retrograde motion works when Earth (T) passes an outer planet (P) as they both orbit the sun (S).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!