2007-02-23 06:30:08 · 10 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
All planets rotate around Sun in same direction. Now, when Mercury is behind the Sun (watched from Earth) looks like Mercury is going back. That's the period when we say Mercury is retrograde. There are points when Mercury changes its moving from retrograde to direct and vice verse, when we say Mercury is stationary. Both are astrological terms.
2007-02-23 07:03:13 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Timekiller has a good answer.
When you plot their position against a star chart, all planets appear to move in the same general direction.
Planets that are closer to the Sun than we are will appear to move the wrong way for part of the time when they are on the other side of the Sun (as seen from Earth).
Planets that are further from the sun than we are, move slower than us on their orbits. Every time we lap them, they appears to move backwards among the stars for a period of time.
In all cases, the apparent rate of retrograde motion is so small that the planet is never seen to rise in the west and set in the east. The apparent rate of a planet among the stars is less than a degree per hour. In fact, it is less than one degree per day. Remember that the apparent movement of the sky (because of Earth's rotation) is 15 degrees per hour -- or 360 degrees per day.
So this retrograde motion is not something you see just by looking up at the planet.
2007-02-23 07:51:10 · answer #2 · answered by Raymond 7 · 0⤊ 0⤋
Retrograde means opposite rotation. All the planets (except Venus) rotate on their axis in the same direction, CCW as seen from the Sun's north pole looking down. Mercury does not rotate retrograde, however Venus does.
2007-02-23 06:37:58 · answer #3 · answered by stargazergurl22 4 · 1⤊ 0⤋
When you pass another car on the highway, observe the visual relationship between the other car and the horizon. Normally, the car would appear to be moving in front of the horizon in the same direction as you. When you pass, more horizon is revealed in front of the other car and the horizon behind it gets gobbled up. Relationally, the other car has changed direction. Once you're far enough away, the illusion passes and the other car is moving forward aginst the background.
When we look at the night sky, the normal direction for things to move is Westward. The outer planets "move" at a different speed than the stars, but at certain times they stop and go "backwards". This is most obvious near "opposition", when the planet is opposite the Sun. That's because Earth is passing them in orbit around the Sun.
Mercury and Venus are a different case because they are closer than the Sun, so they can't be at "opposition". In that case, they lap us. We see Venus travel relatively Eastward as it comes around from behind the Sun, then stop and turn West to cross in front of it, etc.
"Retrograde" refers to the observation that a planet appears to be travelling "backwards" from its normal course relative to the stars.
2007-02-23 07:09:53 · answer #4 · answered by skepsis 7 · 0⤊ 1⤋
Retrogression is a COSMIC PHENOMENON that should occur at least once in a Planet's life time as scientists say...
It is the time when the planet stops spinning round itself to the same direction...pauses for a little while, and then start turning the opposite side for some time.....
Later it will go back again to its normal motion...counter clock wise...
A couple of years ago, on the month of Aug. or Sept. , that phenomenon occurred to Mars...!!
IT IS CONFIRMED THAT EARTH WILL BE SUBJECTED TO THE SAME ONE DAY...IT COULD BE HAPPENING SOON...
Could you imagine how things will be at that day>>>>>The sun will rises from where it sets now...
This is awesome....
The issue Worth saying here is that "Muslims" knew about that more than 1400 years ago...
Modern science just barely knew about this in the 20th Century...
Isn't that worth wondering "HOW COME" they knew about it that long time back....!!!
I thought so....
2007-02-23 07:21:19 · answer #5 · answered by FOREVER AUTUMN 5 · 0⤊ 0⤋
Due to the motion of the Earth, Sun and an observed planet, planets can "appear" to move backwards in our night sky from their usual motion. This is called retrograde motion.
2007-02-23 06:37:11 · answer #6 · answered by rscanner 6 · 0⤊ 0⤋
because of the relation of the orbit of earth to mercury, during the day in certain parts of the world, if you were to track the trajectory of Mercury, it would appear to move across the sky in one direction for a period, and then stop and move the opposite direction for a bit. The part when it stops and reverses direction in the sky is called the "retrograde" part.
2007-02-23 06:36:42 · answer #7 · answered by Anonymous 3 · 0⤊ 0⤋
It means that nothing has changed. It's the same every day. Because every day is a sunny day on Mercury. Because Mercury is the closest planet to the sun
2016-05-24 02:58:09 · answer #8 · answered by Anonymous · 0⤊ 0⤋
Mercury appears to be traveling backwards from the motion it was once going due to Mercury being inside the orbit of Earth.
2007-02-23 06:51:07 · answer #9 · answered by bldudas 4 · 0⤊ 0⤋
It has astrological (if you're into that) significance, too. If merc is retro, the things associated with merc (communications, communications devices, travel) are considered to be more apt to breakdown or move slower.
That's not "scientific" of course but all part of the cultural lexicon.
2007-02-23 06:38:37 · answer #10 · answered by kerridwen09 4 · 0⤊ 0⤋