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.
Facts about Phobos. 1  Phobosâs orbit is so fast it would appear to an observer on the planet to rise in the west and set in the East twice each Martian day. 2  As Phobos orbits, it is getting closer to the planet as time goes by. 3  Phobosâs shadow has been photographed on the surface of Mars by several spacecraft.