Talk:Apparent retrograde motion

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Please note. In Auguest 2009, this article was moved from Retrograde and direct motion.
All of its talk, history and log pages went with it because it was decided that virtually all
the article itself was about Apparent Retrograde Motion. Retrograde and direct motion now
directs to Retrograde motion, not here. The first 15 sections below were created before
the renaming took place and may discuss topics that are no longer present.
--RoyGoldsmith (talk) 01:22, 19 August 2009 (UTC)


Im looking for an authoritative source that uses the term retrogradation. If there isn't such a source, I still like the idea of the word as it is defined here, but I'd like to know if this word is actually used atm. Lir 15:09 Nov 4, 2002 (UTC)

(three and a half years later), i removed the term 'retrogradation' from the article; a google search suggests it's meaning have more to do with chemistry. 15:23, 11 March 2006 (UTC)
Actually it simply means retrograde motion. Limiting it to apparent retrograde motions appears to have been unjustified. kwami 22:11, 11 March 2006 (UTC)

Orphan Mystical Paragraph[edit]

I removed:

In Religion
what is interesting here is to know that the religion of muslims (islam) talked about this motion through the Prophet Muhammed9(SAW), by saying that sun someday will rise from west after three days of not rising and this will be a sign of groups of group of signs before the day of judgment.

Since this is way OT, having nothing to do with retrograde orbit (since this would have to affect rotation not orbit), and since prophecy doesn't lend itself to verification. Dominick 12:06, 30 Jun 2004 (UTC)

Something similar had showed itself, as an 'External Link'

"Muslims knew about this thousands of years ago. To read more go to (iam not advertising)."

I have removed it on the grounds that the tone is distinctly un-wikipedia-ish, and also, as a forum, the content may be volatile. A link along the same lines but to a proper website, not a forum, can certainly be added if someone can find it. 23:34, 23 May 2006 (UTC)

--- True enough that Muslim texts do mention the Sun rising from the West. However, muslim texts also allude to the sun moving in it's own exclusive orbit. Is it farfetched to ponder the possibility of the Orbit of our solar system meshing our coming near to the orbit of another solar system? Would it not create the same effect of our sun or a sun rising from the west?

Dr. Maurice Bucaille in his brief yet informative booklet entitled "The Bible, the Qur’an and Science" edited by Dr. A. A. B. Philips writes:


Today, the laws governing the celestial systems are well known. Galaxies are balanced by the position of stars and planets in well-defined orbits, as well as the interplay of gravitational forces produced by their masses and the speed of their movements. But is this not what the Qur’an describes in terms which have only become comprehensible in modern times. In chapter al-Ambiyaa we find:

“(God is) the one who created the night, the day, the sun and the moon. Each one is traveling in an orbit with its own motion.” Qur’an,21:33

The Arabic word which expresses this movement is the verb yasbahoon which implies the idea of motion produced by a moving body, whether it is the movement of one’s legs running on the ground, or the action of swimming in water. In the case of a celestial body, one is forced to translate it, according to its original meaning, as ‘to travel with its own motion.’

In my book, The Bible, The Qur'an and Science, I have given the precise scientific data corresponding to the motion of celestial bodies. They are well known for the moon, but less widely known for the sun."... - Dr. Maurice Bucaille

- Abu Raihanah Chris Medlock ---

--- —Preceding unsigned comment added by (talk) 05:05, 26 January 2009 (UTC)

Eeh, this page is for discussing the qualities of the article Retrograde and direct motion, not any "revelation" this or that, and regarding "precise scientific data corresponding to the motion of celestial bodies": modern science (available to christians, moslems, jews and atheists alike) provides painstakingly precise truly scientific data, since this article is about science, not religion, nor pseudoscience. ... said: Rursus (bork²) 15:25, 25 June 2009 (UTC)

Circular reference[edit]

This article suggests looking at Retrograde for the musical term, but that now redirects to this article. What's up? Confusing Manifestation 16:51, 30 January 2006 (UTC)

That redirection and suggestion are now fixed. The Rod (☎ Smith) 18:25, 27 March 2006 (UTC)

Error in image[edit]

Like that ..

In the 2nd image ("Like that") with a retrograde motion, either the symbols A2 and A4 are swapped (if you start from left A1), or there are 2x A1 !

Well, I cannot edit swg graphics... Would you correct it?

The image is correct, so no need to correct it! It should be that way. ... said: Rursus (bork²) 15:12, 25 June 2009 (UTC)
Sorry, I misread you: A2 to A4 are in correct order. The error was that A5 was replaced by A1. Somebody silently corrected the error by producing a new image, not me. ... said: Rursus (bork²) 15:14, 25 June 2009 (UTC)
Actually, the second image in the article is Retrogradation.svg. Until a few minutes ago, that file also contained the error. I have uploaded a corrected version into Wikimedia Commons.Peter Chastain (talk) 11:56, 29 July 2009 (UTC)

Apparent Retrograde Motion[edit]

The article says that planets beyond the Earth's orbit appear to switch direction. I think it's true to say that the planets inside the Earth's orbit would also exhibit this behaviour as they periodically overtake the Earth, but it is not seen because it always occurs during the day time.

I think you're mostly correct, except it might actually be observable. ... said: Rursus (bork²) 15:10, 25 June 2009 (UTC)
What you mean to say is that they take place too close to the sun to be visible because of the glare and because the planets (from our viewpoint) are in new phase (just like the new moon) and show only small amounts of reflectance. It happens over several week's time, day and night.SkoreKeep (talk) 21:35, 1 August 2014 (UTC)

Retrograde motion.[edit]

Retrograde motion and venus. Remarkable. —Preceding unsigned comment added by Merwin21 (talkcontribs) 01:42, 22 November 2007 (UTC)


Have edited article to describe Pluto as a planetoid, not a planet as was implied by the original text. —Preceding unsigned comment added by (talk) 23:54, 24 July 2008 (UTC)

Planetoid is another name for asteroid. Pluto is not an asteroid/planetoid.--Systemizer (talk) 09:53, 30 June 2009 (UTC)
Pluto is now a dwarf planet. --RoyGoldsmith (talk) 01:02, 19 August 2009 (UTC)

Definition of "north orbital pole" contradicts that given in the "Orbital pole" article[edit]

See the sentence "The north orbital pole ... is defined to be south."

The same sentence in the "Orbital Pole" article is "The north orbital pole ... is defined to be north."

I'll leave it to an expert to decide which is right. (talk) 17:21, 15 October 2008 (UTC)

Couldn't be found, so must have been fixed. ... said: Rursus (bork²) 14:57, 25 June 2009 (UTC)


I've just edited this bit to make it clear that the explanation given is not accepted by all astrologers. I've credited it to "a contributor" because I can't make out from the history who put it in. If whoever it is wants to sign it they're welcome.Wombat140 (talk) 21:02, 11 March 2009 (UTC)

The "contributor" credit doesn't seem appropriate for wiki. It sounds like the editor is just guessing at what astrologers say without any research. (talk) 22:47, 4 June 2009 (UTC)
The corpus of astrological writings is a chaotic collection of diverse subjective opinions. Self-evident logical coherence is the only valid criterion of trustworthiness.--Systemizer (talk) 09:30, 30 June 2009 (UTC)
This quote needs revising unless a more convincing argument is developed to show why the Roman Church in the era of Inquisition pursued an error sticken course."Ancient Greek astronomer Ptolemy in 150 AD believed that the Earth was the centre of the Solar System and therefore used the terms retrograde and prograde to describe the movement of the planets in relation to the stars. Although it is known today that the planets revolve around the sun, the same terms continue to be used".
Evidence that Christians free of Catholic influence; Jews, Arabs as well as astronomers outside the western Sphere of influence may not have been so misguided.

Weatherlawyer (talk) 19:50, 23 January 2016 (UTC)


The text has 2009-2010, but the picture of Mars has 2003. —Preceding unsigned comment added by (talk) 14:57, 22 May 2009 (UTC)

Fixed. Typically this kind of error can be smashed at sight, so be bold, kind of. ... said: Rursus (bork²) 06:42, 25 June 2009 (UTC)

Some pure rubbish[edit]

Section Retrograde motion in astrology contains some very low-quality logic:

Only the inferior planets—Mercury and Venus—can become genuinely retrograde, since their retrogradeness is produced by their own motion.

The "since" subclause is false. All motions are relative, involving Earth's motion and the planet's motion, and no planet travels retrogradely as seen from a fixed point far above the north pole of sun. Hence the entire clause is false. ... said: Rursus (bork²) 15:39, 25 June 2009 (UTC)
And the source provided claims nothing of that kind. ... said: Rursus (bork²) 15:41, 25 June 2009 (UTC)

No, comment? Then, I'm going to delete the unimportant text making that erroneous claim. ... said: Rursus (bork²) 06:57, 3 July 2009 (UTC)

Inferior retrograde[edit]

Can we get some figures or animation involving the process of retrograde involving an inferior planet? As the article says, "Mercury in retrograde" is a very common astrological phrase, but there is not enough description differentiating how the retrograde motion would appear or its frequency. MMetro (talk) 09:36, 11 August 2009 (UTC)

The problem is that Mercury and Venus display retrograde motion from Earth only at superior conjunction when the sun is between the Earth and the body. Not only is the sun blocking out the view, but the glare is far too high to see the motion in any case, as it obviously can only be viewed in the daytime. If it could be seen, it would appear just like it does for the outer planets; the body would pass the sun, appear to stop and then pass back behind the sun again, then stop on the other side and pass it a third time; as it is, it appears to wane as a morning star, spend an apparently inordinate amount of time out of view before re-emerging as an evening star. The frequency is once every synodic period of the planet; for Venus that's 584 days, for Mercury it's 116 days. SkoreKeep (talk) 15:38, 23 June 2014 (UTC)
Don't know what I was thinking there. It happens when the body is between the Earth and the sun. The sun doesn't block the view, but the glare of it does; not only that, but the body is in a "new" phase, showing 90% or more dark side to Earth only. SkoreKeep (talk) 21:42, 1 August 2014 (UTC)

Picture of the Day[edit]

Now I get it ;). (talk) 10:43, 11 August 2009 (UTC)


WASP-17b is the first planet (really exoplanet) discovered that exhibits true retrograde motion, like Triton. The article about Retrograde and direct motion talks mainly (or exclusively, I'm not sure) about apparent retrograde motion. Now that a retrograde planet has been observed, this should be made clear, possibly with links to Triton and WASP-17b. I'd do it myself but I'm not an astronomer. --RoyGoldsmith (talk) 12:47, 14 August 2009 (UTC)

I've split this into two separate articles for apparent and actual motion. Zbayz (talk) 18:05, 15 August 2009 (UTC)

Do we really need an astrology section?[edit]

The astrology section is nothing more than some evidence-free claims made up out of whole cloth. If you check the citations, they say things like "When a person is born with Mercury Retrograde, it indicates that in past lives there was a discrepancy between the words the native was speaking, and what they truly thought on their own."[1] Why does this information deserve to be in an encyclopedia? Gary (talk) 17:33, 15 August 2009 (UTC)

Yes, we do. I added the section back, and modified it. It was frankly surprising to see the topic not covered. While you may consider astrology inherently subjective, it is a subject with a vast literature and easily meets all our criteria for inclusion, and our standard is reference-ability, not truth. There is, moreover, a broad consensus at least among Western astrologers about the tradition and what things mean within it. Treat it as a folklore subject, if you like. Omission of the subject might be considered an instance of positivist bias, and there's a lot of that going around. The subject is indeed large enough to support a potential article on retrograde motion in astrology, but should be at least mentioned with an introductory mention here. I added back part of the old section, removed particular interpretations, and added a reference. - Smerdis of Tlön - killing the human spirit since 2003! 15:32, 12 August 2011 (UTC)

We need separate discussion pages[edit]

The discussion links at the tops of the articles Apparent retrograde and direct motion and Retrograde and direct motion both direct a user to the same talk page. This is confusing. Both articles should have their own talk pages, because not everything on the talk page is applicable to both articles. For example, when I questioned the need for an astrology section, I based that question according to Apparent retrograde and direct motion, which has an astrology section, not on Retrograde and direct motion, which lacks an astrology section (as it should). Gary (talk) 18:32, 16 August 2009 (UTC)

OK. I've started up a talk page for Retrograde and direct motion by cut-and-pasting this section and the WASP-17b section above to the R&DM talk page. Any further discussion on this page should pertain solely to apparent motion. --RoyGoldsmith (talk) 19:41, 16 August 2009 (UTC)

There should be a section about how this affected ancient astronomers[edit]

This is a decent article, but I feel like there needs to be a section covering the effect this had on astronomers such as Aristotle, Eudoxus, etc. This apparent retrograde motion is what caused ancient astronomers to begin using concepts such as equants, eccentrics, and epicycles. It also led to Eudoxus' nested sphere model of planetary motion. These subjects are extremely important when looking at the history of science and since they were completely caused by apparent retrograde motion, there should be a section discussing these effects. Nro87 (talk) 20:01, 24 May 2013 (UTC)

Do you know of relevant sources? IRWolfie- (talk) 19:30, 28 June 2013 (UTC)


This article is about Apparent retrograde motion. We don't mention fringe beliefs in mainstream articles without good reason, otherwise that would give them undue weight (WP:ONEWAY). Issues with Astrology should not be discussed in this article on Apparent retrograde motion since there are no independent reliable sources which "connect the topics in a serious and prominent way". IRWolfie- (talk) 23:45, 28 June 2013 (UTC)

Agreed. The change (diff) with talk about "Psychological astrology ... point toward an interior reality" is not appropriate for a scientific topic. Johnuniq (talk) 03:23, 29 June 2013 (UTC)
I don't know how much detail is appropriate for this article, but there should definitely be a place for information about the notion of retrograde in astrology; while not fact-based, it is an important thing culturally, and does deserve a place in the encyclopedia. I'll try to find some sources and write up a (probably short, but) improved treatment of it within the next couple days, but I don't think the section should be cut out entirely. Abeg92contribs 07:12, 7 July 2013 (UTC)
On second thought, a better solution might be to have a separate page for the notion of retrograde in astrology, with a disambig note at the top. I couldn't make it very long, but maybe someone else could?Abeg92contribs 07:24, 7 July 2013 (UTC)

When exactly the reversal happens[edit]

One thing that puzzled me - and which the article doesn't seem to currently cover - is exactly when the direction reversal happens. In terms of Earth and Mars, I guess it's basically when the direction of the Earth is directly at Mars, i.e. the tangent line of the Earth's orbit at Earth's location passes through Mars. And the regular motion resumes when the tangent line again crosses through Mars on the other side. Maybe worth mentioning? Wknight94 talk 14:54, 4 March 2015 (UTC)

No. The instant to which you refer is called, by our hypothetical friends the Martian astronomers, the greatest Elongation (astronomy) of Earth. At that time the Earth is moving along that tangent rather than through it, thus its motion has no crossways component, thus is not affecting the apparent motion of Mars at all. At that moment, we see the real, posigrade motion of Mars against the starry background. The retrograde loop of Mars is something we see during a certain interval between the two times Mars sees us at maximum elongation. Alas, I lack the math to devise a formula to identify it more narrowly, even in the simplified hypothetical case of circular coplanar orbits. Jim.henderson (talk) 01:36, 6 March 2015 (UTC)
So, if I'm not even correct, and you're not precisely sure either, even more reason to include more detail, IMHO. Seems like a very basic question that is going unanswered in the article. Maybe we can find a bit of math out there - hopefully in a reliable source. Wknight94 talk 12:38, 15 March 2015 (UTC)