Planets travel in an aparent irregular way. Their movement along the space from west to east, is interrupted during brief intervals of time by an apparent retrograde motion from east to west. This apparent retrograde motion is preceded by a speed decrease until planet stops, then, it goes back to a stationary position again and resumes its direct motion from west to east.
The planets move eastward against the background of fixed stars with the exception of Venus, Uranus and Pluto moving westward as seen in Earth's sky . This apparent retreating movement is called Retrograde motion. It is illusion created by Earth's movement going by outer planets in their respective orbits.
Assuming we can turn on the lightbulb from any distance with a device. We can gradually increase the distance that separates us from lightbulb, in this way, if the speed of light is finite we can see a temporary delay between the moment we turn on the lightbulb and the moment in which we observe its light.
