Mars is our neighboring planet. We also call it the “Red Planet”. But did you know its motion is sometimes quite strange or not as usual as that of our own planet. This motion is called apparent retrograde motion of mars. It’s not an actual or motion. However, we can call it a natural perspective motion. What’s that? We’ll see that in this article.
WHAT DOES RETROGRADE MEAN?
There is a Latin word called “retrogradus”. Here, “retro” means backward and the term “gradus” refers to step.Hence the word means backward motion. So, retrograde motion means the backward motion of a planet with respect to the other planets in the same system
WHAT IS APPARENT RETROGRADE MOTION?
By adding another term “Apparent” to this word, we make this motion not actual or not real. It becomes just a perspective thing. That means we can observe that motion only from a certain vantage point. There is another kind of motion: prograde motion or direct motion. In this motion, the planet moves in the same direction as the other planets in the system. So, in the apparent retrograde motion, as the earth passes a superior planet, mars, the latter will seem to move in a reverse motion across the sky of the former.
HOW DOES IT OCCUR?
Initially, Mars moves eastward. Earth also moves eastward. So their motion is in the same direction. Then gradually, as time passes, mars stops and then starts moving westward. The position at which the sun, earth and Mars align in a straight line is called opposition. So, the motion appears retrograde in the earth’s sky. It’s just a natural perspective effect. It depends on which planet we have taken as the vantage point. Because we are not going to observe this from Jupiter or Saturn. Because they are the superior planets for Mars. This video will be very helpful if you want to understand it clearly. https://www.youtube.com/watch?v=1nVSzzYCAYk
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