whats the effect and the cause of retrograde motion in earths sky on both inferior and superior planets?
http://www.scienceu.com/observatory/articles/retro/retro.html
The effect of retrograde motion in the Earth's sky on both inferior and superior planets is an apparent reversal of their regular eastward motion. This occurs when Earth overtakes and passes these planets during their orbit around the Sun.
The cause of retrograde motion for inferior planets (such as Mercury and Venus) is their orbit being closer to the Sun than the Earth's orbit. As we observe from Earth, these planets can never be on the opposite side of the Sun, so they appear to exhibit retrograde motion when they come closest to us during their orbital journey.
On the other hand, the cause of retrograde motion for superior planets (such as Mars, Jupiter, and Saturn) is our relative positions in our orbits around the Sun. As Earth moves faster on its inner orbit, it occasionally catches up to and passes these superior planets. This creates a temporary illusion of the planets moving backward or in a westward direction compared to their usual eastward motion.
To understand and predict retrograde motion, you can follow these steps:
1. Observe the apparent motion of the planet in the night sky over several weeks or months.
2. Track the planet's path against the background stars and note its direction and speed.
3. If you notice the planet moving eastward (in the same direction as most celestial objects), then it is not in retrograde motion.
4. If the planet's path slows down, stops, and then starts moving backward or westward, it is entering its retrograde phase.
5. Continue observing until the planet's motion shifts again, and it resumes its eastward path. This marks the end of the retrograde motion.
Understanding the orbital characteristics and relative positions of the planets can help you explain and predict retrograde motion.