# Table of dates for planet retrograde motion

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Is there a table which shows the dates of the planets retrograde motion? I want to know at which date a certain planet will start the retrograde motion.

Check this website out - it has a table that might help you: Website

This site is also a little sketchy (it's for horoscopes and stuff) - but it still has some accurate information on the exact dates of retrograde: Website

Hope that helps!

There is an annual publication "Astronomical Phenomena for the Year YYYY" published by the United States Naval Observatory and United Kingdom Hydrogrphic Office. Page 6 of the 2018 edition gives a table of conjunctions, stationary, oppositions, etc. for the planets. See http://aa.usno.navy.mil/publications/reports/ap18_for_web.pdf

For the superior (outer) planets, the earlier stationary date is when it starts its retrograde motion. The second stationary date is when it ends its retrograde motion.

EDIT: It turns out calsky.com will do these calculations for several years out, including other calculations commonly found in almanacs. Sample page:

https://www.calsky.com/cs.cgi?cha=7&sec=6&sub=3

The best place to start on this site isn't the home page, but rather the TOC:

https://www.calsky.com/cs.cgi/TOC?&f=

I now consider my answer to be better than @JohnHoltz's :)

Note: I saw @JohnHoltz's answer while I was typing out my answer, so some of the below may be redundant. Upvote/checkmark his answer, not mine.

This isn't really an answer, but too long for a comment:

• I was disappointed how difficult it was to find this information, given how easy it is to calculate and how many other astronomical phenomena are listed in various places on the Internet.

• When a planet starts or ends retrograde motion, it is temporarily stationary before it "turns around". Thus, some astronomical sources will say "Jupiter stationary" instead of "Jupiter starts retrograde motion".

• Based on the above I google'd"jupiter stationary" "mars stationary"(as quoted; google tries to correct one of the stationary's to stationery, so I had to click one more time to do the search correctly), and finally found something: http://aa.usno.navy.mil/publications/docs/ap.php

• The publication doesn't mention retrograde, but it does mention when a given planet is stationary and provides a brief description of each planet's position in the sky for the given year.

Because this seems like a fairly easy calculation to make, I may do it myself and update this answer.

## Planets in Retrograde 2021 Dates, Timings

Retrograde Planets 2021 Calendar- The article on the list of Retrograde Planets 2021 Dates is provided by AstroSage for the benefit of its readers. This will guide you about the retrograde motion of planets in 2021 and their transit along with their dates, time and signs in which they will retrograde. You will also get to know about the impact of their movements.

The planets play a vital role in supervising our everyday activities and the same has been conceded by most of the people. Their ascendancy brings vital changes in the thoughts and lifestyle of the natives. Their transits effectively manifest these refinements in the lives of individuals. The scientific studies talk about nine planets however as per the heritage of Vedic Astrology, a total of seven planets are taken into contemplation.

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There is a strong belief that these planets touch human existence in some or the other form. The two natural energies are the Sun and Moon, one is considered to be the father and soul of a being while other is the mind and nurturing mother. The sage Jupiter is the blessing and constitutes wisdom and prosperity while Mercury bestows intelligence. All of them draw out the meaning in the formation of life. Let us comprehend about the occurrence of retrogression before moving ahead to their dates and collision.

For the convenience of the readers, AstroCAMP has provided a very useful set of tables of retrograde planet 2021 dates list. With the help of this list, you can easily get the date and time of when the planets will enter or transit into its retrograde motion in the year 2021.

Most of us acknowledge this fact that planets play a significant role in our lives. It is accepted by most of the natives that planets play a very important role in conducting our day to day lives. Most of them possess the potential to influence the lives of the natives residing in the universe in an important manner. Astronomy mentions the presence of nine planets, but as per our traditional Vedic astrology, only seven of them are taken into consideration.

It is believed that these planets affect human lives in one way or the other. For instance, the Sun is considered to be the governor of father, soul and confidence and Jupiter represents wisdom, intelligence, positivity and overall prosperity of the native. Now , before moving further to the retrograde planets 2021 dates and results that they will actually bring for us, first let us understand what is the actual meaning of retrograde.

As already mentioned above, all the nine planets undergo various movements in the celestial sphere and retrograde is one of them. Out of the seven planets that we take into account as per our traditional Vedic Astrology Sun and Moon always have direct motion whereas other planets like Mars, Jupiter, Venus, Mercury and Saturn have direct or indirect motions.

There is a continuous change in the zodiac due to the difference in the motion or speed of the planets, one planet overtakes and transcends another, then apparently starts to slow down, stop and move backwards. The apparent stopping of a planet is a "stationary" position the evident backward movement is known as "retrograde". In hindi language, it is called “Vakri” and the planets are known as the “Vakri planets “ The traditional approaches of astronomy believe that each and every planet revolves around the Sun, but it is not the case in astrology, according to which the Earth is taken as the reference point and the planetary movements are demonstrated.

However, the reality is that none of the planets actually move in a backward motion but only appear to do so when its relative motion is viewed from the Earth. Many people often consider or fall into the misconceptions that retrograde planets only produce malefic results or ill effects, which is not always the case. It can generate both positive and negative effects depending upon its placements in your horoscope.

Finally, now let us look at the retrograde planets date 2021 mentioned in the table below:

 PLANET Retrograde starts Retrograde ends From To Mercury January 30, 2021 20:54pm February 21, 2021 05:49 am Aquarius Capricorn Mercury May 30, 2021 03:47 am June 23, 2021 02:50 am Gemini Taurus Mercury September 27, 2021 10:12 am October 18, 2021 20:11 pm Libra Virgo Jupiter June 20, 2021 20:49 pm October 18, 2021 11:39 am Aquarius Capricorn Venus December 19, 2021 16:32 pm January 29, 2022 14:55 pm Capricorn Sagittarius Saturn May 23, 2021 15:35 pm October 11, 2021 03:43 am Capricorn Capricorn

After looking at the Retrograde planets 2021 dates, let us now go through that effects that they bestow upon us in detail :

Mercury retrograde is one of the most significant celestial events as it happens two to three times in a year whereas the retrograde motion of the other planets happens only one time in the year or sometimes it does not happen at all. Hence, while looking for the retrograde planets dates 2021, natives will primarily search about the date and timings of the Mercury retrograde.

It is a well known fact that Mercury is considered as the natural significator of speech and communication abilities. It also governs the business sense, observation and organisational capabilities coupled with a charming and youthful attitude. Mercury is hailed as the messenger and it is a planet that is generally associated with smooth exchange of ideas and information. This particular planet revolves around the Sun in approximately 88 days thereby attaining the status of the fastest planet in the solar system after the Moon.

When it is present in its exalted state in the horoscope, it amplifies the qualities mentioned above. When it is present in its own sign or in benefic placement, it provides the native with high intellectual prowess and blesses them with a pragmatic and productive approach. When it is present in its debilitated condition, Mercury gives hesitation, low memory, difficulty in conveying or expressing your ideas to others, affected by unknown fears and misconceptions. In addition to this, the native may also face problems related to allergy, skin and nervous system. Since it is neutral and dualistic in nature, it confers the results on the basis of its conjunction or placement with other planets in the horoscope.

If it is positioned with malefic planets then it provides the natives with negative results and when placed with benefic planets the results obtained can be vice- a- versa. Mercury generally has good effects on other planets, but when it becomes retrograde, its influence becomes even stronger. In case Mercury has negative influence on any other planet, Mercury retrograde can cause serious consequences. If Mercury is at its elevated point, then Mercury retrograde produces excellent results. A person with benefic retrograde Mercury can expect sudden gain of wealth, farsightedness with sharp communication and decision making skills. While debilitated Mercury puts a negative effect on the economic condition and decision making of the native in its retrograde motion.

Remedy - Chant the Mercury Mantra daily during the Mercury Hora.

In astrology, the planet Venus is a symbol of the joy one gets in life. In the world, the best pleasure comes from a woman. Therefore, it is also considered representative of the feminine energy. Venus is the lord of two signs Taurus and Libra which occupies the second and the seventh house of natural horoscope.

Among these, we consider money, food and clothes from the zodiac sign of the Taurus. From the seventh, which is governed by Libra, which confers one with intelligent and abstract thinking. Libra is also hailed as the natural partner in the zodiac system. So, whenever Venus transits beneficially in our chart it confers one with love, attention and flow of money. It is given the status of the most beneficial planet as it is regarded by the natives as the most brilliant one.

Rather than the earth, it remains in close proximity to the Sun. Hence, in some situations, it appears in the middle of the Earth and the Sun. Among the list of retrograde planets in 2021 dates, the retrograde motion of Venus is also quite important as the planet of love, harmony, compassion, beauty, luxury turns retrograde once in eighteen months.

Meanwhile, the exalted sign of Venus is pisces and it is debilitated in the sign of Virgo. Libra is considered as its Mooltrikona sign. When in exalted position in the chart, it makes one romantic, lavish, beauty lover, highly ambitious with great persuasive skills. The love life of the native flourishes and they easily enjoy the company of the opposite gender.

On the other hand, debilitated or afflicted Venus may make one dissatisfied, skeptic, selfish and demanding in relationships, thus, creating obstacles and hurdles in their relationship and marriage.This is why the significance of retrograde Venus increases to some extent. Now when the same planet is in retrograde motion, the auspicious results of the planets decrease significantly.

The native with such transit oftens feels shy, low in confidence and may feel awkward while moving around in social circles. To some extent, issues related to love and wealth may remain stagnant and one may face seemingly tough challenges, ups and downs in relationships. The retrograde Venus provides a reduction in the amount of marital bliss and happiness in a person's life. Therefore, it can be concluded that the planet that usually produces fruitful results leads to the most non-auspicious results when going in retrograde motion.

Remedy- Recite the Lalita Sahsranaam daily to increase the auspicious effects of Venus. You can also chant the Venus Mantra daily during the Venus hora.

The planet Jupiter or brihaspati holds a prominent place in the planetary cabinet as a minister and is also hailed as Devguru, the master or mentor to the gods. It is a very auspicious planet and is the significator of speech, learning, intelligence, scripture, religion and knowledge.

Jupiter is considered as one of the most benefic and auspicious planets in astrology. It is the largest planet in the solar system therefore, therefore anything that is magnifying and expansive is generally associated with Jupiter. It is benevolent and protective in nature and when in a strong position in horoscope blesses the native with luck, prosperity, wisdom, fame, spirituality, good morality, progeny, devotion and spirituality. Its importance can be gauged from the fact that it rules over the “Karkatva” or is the natural significator of five important houses in horoscope. Jupiter also indicates sustenance of money in vedic astrology, which indicates that its strong presence bestows one with prosperity and abundance of wealth.

It rules over the ninth sign Sagittarius and twelfth sign Pisces of the natural zodiac. It gets exalted in the sign of cancer and gets debilitated in the sign of the Capricorn. So, when the jupiter is strong in one’s birth chart, they remain more focused and tend to achieve targets or goals more easily than others.

They are optimistic, more expressive, protective and intuitive in their day to day affairs. Some of them can also expect to earn fame in society. On the other hand, when it is in afflicted state, it tends to make one lethargic, dependent on others and circumstances, pessimistic, excess overindulgence which may result in improper utilisation of resources, immorality and distrust on others.

Meanwhile, when Jupiter is in retrograde motion often finds success when the chips are down, they begin doing things where others become disheartened and the unique ability to find success in the projects which have been dumped or discarded.

They find opportunities working out for them with ease, which makes them a little surprised. They have good foresight and determination that provides them with the capability of reviving things like bringing a phoenix back from ashes. Hence, it can be concluded that Jupiter retrograde can bring some positive results prominently.

Remedy- Respecting your elders, mentors, teachers. Reading or listening to the stories of Vaaman avatar of lord Vishnu will bring auspicious results of Jupiter.

Saturn is often considered as the devil or evil trying to get hold of persons and putting them in the net for years to suffer in grief and isolation. Generally, considered as a malefic planet which is cold and icy in its attributes as it rules over the “shishir” ritu which is considered the coldest season in the indian subcontinent.

As the nights are generally longer and days are short, which represents that which signifies its slow movement and indicates that good results can take time to come during the Saturn periods. It rules over the Capricorn and Aqaurius zodiac signs. Libra, the sign of Venus is its exaltation point and Aries governed by Mars is where it is at its weakest or debilitated state.

Though people associate planet Saturn with grief, sorrow but they have to understand that it is a hard task master, a teacher who teaches the necessary life’s lesson by making you go through hardships and struggles. Saturn signifies discipline, hard work, changes and is a planet that guides and forces you to take action at the same time. When positioned in its exalted state or in benefic placement in the horoscope, it makes the native responsible, reliable, sincere, faithful and honest.

It also makes one dedicated towards a cause, provides admirable leadership qualities and such native understands the value of time. On the other hand, its debilitated state makes one lethargic, filled with victim complex, careless, inconsistent and unfocused in his state of affairs. As Saturn is a planet of common people and denotes mass leader, which indicates that it is an important planet for those who are already in politics or trying to get their foothold in it.

But, when Saturn is in retrograde motion, it makes people shy, uneasy, insecure, lacking self assurance which they tend to guard through arrogance and egoistic attitude. This is why they often become secretive and isolated. They often tend to believe that they are guided by some unknown phenomenon, force which often sees them not taking responsibility for their actions.

Remedy- Donate Mustard oil, black peas or pulses on Saturday to ward off the evils of Saturn. Worship of Kaal Bhairav, the incarnation of Lord Shiva is also very auspicious and helps to mitigate the ill effects of Saturn.

Mars, the planet which is hailed as the commander in chief in vedic astrology and is the planet responsible for courage, bravery, determination and administrative skills. It governs over the Aries and Scorpio sign of the natural zodiac which makes initiation and strategy the main powers of Mars.

It is in exalted in the sign of Capricorn which is the tenth house of the natural zodiac which is associated with action, which means it is an action oriented person, and as capricorn is a sign that is denoted with responsibility, the person with exalted Mars is practical, structure and organised in its day to day affairs. It rules over the “Grishm” ritu or the summer season, which makes it the planet full of vitality and energy.

That is why it is also considered to be the generator of an energy source vital for all living organisms existing in this universe. As the natural significator of the third house, it represents the courage, desires and ambitions of a person. Overall, it is considered as a malefic planet, but it makes one protective, warm, generous filled with leadership qualities and never say die attitude which makes them achieve success in each and every sphere of life.

The native with exalted Mars are always driven to be number one and have the capacity to overcome their obstacles with sheer willpower and strength. It makes one good in execution, commanding and courageous. On the other hand, the weak or debilitated Mars makes one highly sensitive, unnecessarily stubborn, not willing to learn from mistakes, vindictive and results in native wasting his/her energy in achieving small things rather than aiming for bigger goals. Hence, the retrograde motion of Mars is also one which should be taken into consideration from the list of retrograde planets 2021.

When Mars is in retrograde motion, the person feels a lack of energy or vitality to finish important tasks. One tends to become afraid of the failures or has unknown fear of rejection which often sees them always in conflict with their desires and ambitions and instead of pursuing them, they tend to leave them in between. They also display unnecessary aggression and often find themselves engaged in petty fights, arguments and legal battles.

Remedy - Chant or recite the Mars mantra daily during the Mars hora. Also, reciting or reading the stories related to Lord Narsimha will help nullify the malefic effects of Mars.

Thank You so much for staying tuned. We hope that you will appreciate this write up of ours on Retrograde planets 2021 dates!!

Think about it this way. You're in a car driving down a freeway. You see a car ahead of you. Your car is going faster than his. So as you proceed down the road and approach his car he appears to be going backward toward you. Now picture the car as you actual pass it. Wave to the driver. In no time you will see him slip into the back seat window. But notice once you pass him and he is now in the rear window he goes from going backward to going slower. He now is trailing or receding from you, but he is no longer going backward. Same thing happens in planets. Hope this made sense to you.

In this "retrograde" motion, neither planet is actually moving backwards it only appears that way during the time that one laps the other.

Mars is retrograde for slightly less than 10 weeks every 2 years

The two planets are like race cars on an oval track. Earth has the inside lane and moves faster than Mars -- so much faster, in fact, that it makes two laps around the course in about as much time as it takes Mars to go around once.

About every 26 months, Earth comes up from behind and overtakes Mars. While we're passing by the red planet this year, it will look to us as though Mars is moving up and down. Then, as we move farther along our curved orbit and see the planet from a different angle, the illusion will disappear and we will once again see Mars move in a straight line.Just to make things a little more odd, the orbits that Earth and Mars follow don't quite lie in the same plane. It's as if the two planets were on separate tracks that are a little tilted with respect to each other. This causes another strange illusion.

Suppose you were to draw a dot on a sky map each night to show where Mars appears as it moves forward, goes through retrograde, and then resumes its forward motion. Connect the dots, and you'll draw either a loop or an open zigzag. The pattern depends on where Earth and Mars happen to be in their tilted racetrack orbits.

From one time that the Earth and Mars are on a line through the Sun (called being in "opposition") to the next opposition is 2.135 Earth orbits. It is in a short period including the time of opposition when Mars exhibits its retrograde motion to an observer on the Earth. The time period between oppositions is called the synodic period.

Obviously, any plantarium type program will illustrate this far better than a text answer, if you put in the correct dates.

As noted in the diagram, such motion occurs at opposition, when Mars is opposite the Sun in the sky, and rises near sunset. (slightly modified from NASA SP-4212)

The retrograde motions of Mars and Uranus in 2003 (Tunc Tezel, apod031216) A composite image created by superimposing images taken on twenty-nine different dates.

## The Astrology Promise of Pluto in Retrograde

Pluto's influence is considered to be evolving, regenerative and transforming. When Pluto's transit is direct (moving forward) we tend to change from the "outside" in as the situations around us typically force us to evaluate our predicaments. When Pluto's transit retrogrades, we reverse this process to an inside-out evolution. Our internal forces seem to break down or redirect us so that we can see our own need for change rather than being forced into the process by others.

To adjust the times for your timezone, add or subtract the number of hours your timezone is from 0 UT. If you live in the western hemisphere (mostly the Americas) you would subtract the number of hours from the time shown on the table. Most of the eastern hemisphere will add hours to the time shown in the table.

## 2021, May 22: Saturn Retrogrades

May 22, 2021: Saturn, the Ringed Wonder, begins its retrograde motion today. The planet is in the southern sky to the upper right of bright Jupiter before sunrise. The planet is at opposition on August 2, and ends its retrograde motion on October 10.

The Ringed Wonder Saturn begins its retrograde motion on May 22. The planet stops its eastward motion on the ecliptic coordinate system and seems to start moving westward compared to the stellar background.

The planet has been inching toward Theta Capricorni. The eastward motion stops and the planet seems to move away from the star.

Retrograde motion is an illusion from the faster moving Earth catching and passing between the sun and the planet.

This regular westward movement of the outer planets was the cosmological problem of the day. What caused the outer planets to seem to back up and at some later date resume their eastward motion compared to the stars?

The answer depends on the placement of the earth in space. Was it unmoving at the center of the cosmos or was it one of the known planets revolving around the central sun?

Ancestral astronomers who thought the Earth was central and unmoving used circles on circles to explain the strange westward motion. The planet was on a small circle that rode on a larger circle that moved the planet backwards compared to the stars at the appropriate time.

Sun-centered astronomers thought retrograde motion was an optical illusion of our faster moving world – revolving around the sun on a circle – passing an outer planet.

Astronomers used their two models to predict the positions of the planets compared to the background stars. Because both used circles, one theory could not out-perform the other with the prediction of the planets’ locations in the sky,

Not until Johannes Kepler determined that the planets revolve on elliptical-shaped orbits, along with Newton’s principle of gravitation, did better models emerge to predict the locations of the planets in the sky.

Many “planetarium” computer programs use the mathematical equations that are derived from Newton’s explanation of gravity. Lunar phases, tides, moon phases, and glamorous flights to the moon and planets are predicted very accurately from the principles of planetary motion.

Precise measurements of Earth’s revolution around the sun did not occur until 1838. Earth is one of the planets in the gravitatioal grasp of an average star.

To find out more about the quest to measure the earth’s revolution around the sun, read Alan Hirshfeld’s “Parallax: The Race to Measure the Cosmos.”

The chart above shows the relative position of Earth and Saturn compared to the sun. On May 22, Earth begins catching Saturn. In the sky, the planet begins to retrograde. The planet rises at about 1 a.m. CDT and appears in the southern sky near sunrise.

As May turns into June, Saturn is moving toward opposition, when our planet is between the sun and Saturn. By early July, the Ringed Wonder rises around 10 p.m.

Earth moves between the sun and Saturn on August 2. As the sun sets, Saturn rises. This is opposition. Saturn continues to retrograde.

After opposition, Earth moves away from Saturn. By early September, Saturn is in the southeastern sky after sunset. The planet’s westward motion continues until October 10. The Ringed Wonder begins its eastward motion again after this date. The planet starts the night nearly in the south.

The pattern occurs every year as our planet catches up and passes between Saturn and the sun.

## APDM Events – Present and Future

2021 —— two events of APDM in 2021

JAN 14 – JAN 30, 2021 – 19 days

Feb 20th, 2021 – APR 27 2021 – 10 weeks and 3 days —– over 3 months of APDM – Wave points out that this is the longest length of days of any other APDM since 2008 on the Thanksgiving night of November 27th, when APDM was first witnessed and discovered by Wave as an event, not just one day, but an event with a beginning and an end. There is a lot more to this particular APDM segment and because it lasts for so long, there is expected reverb on the planet.

APDM Events – Past

Nov. 27 – Dec. 31, 2008 – approximately 35 days
Begins with Urania direct and ends with Saturn retrograde 11/27/08 – day APDM is discovered

Dec.1 – Dec. 20 – 2009 – approximately 19 days Begins with Urania direct and ends with Mars retrograde

Dec. 5, 2010 – Dec. 10, 2010 – rare 5 day cycle – Led by Uranus direct and ending with Mercury retrograde

Dec. 30, 2010 – Jan. 26, 2011 – approximately 28 days – 2nd APDM cycle to begin in 12/10
with Mercury direct and ends with Saturn retrograde

Dec. 25, 2011 – Jan 23, 2012 – approximately 31 days – Begins with Jupiter direct and ends with Saturn retrograde
Wave Rayne led the first online course to occur in all of history to observe “ALL PLANETS in DIRECT MOTION”™ and meditations occuring with over 100 people.

January 30, 2013 – February 18, 2013 – approx 19 days – Begins with Jupiter stationing direct and ends with Saturn retrograde

All Planets Direct Motion™ didn’t occur in the year 2014. There was always at least one planet retrograde the entire year from Mercury to Pluto.

December 25th, 2015 – January 6th, 2016 – about 11 days – Uranus stations direct and Mercury stations retrograde
Article on FB and other sites goes viral and over 100,000 read it and more than 10,000 people begin to meditate together

January 8th, 2017 – February 6th, 2017 – about 28 days – Mercury stations direct and Jupiter stations Rx
Close to 20k people are meditating together around the world at the same time during APDM for global peace and abundance for all, shifting the collective field of consciousness from scarcity and fear to prosperity and hope.

Jan 2, 2018 – March 8, 2018 – about 65 days!

## Understanding Transits and Retrogrades of Mars

As one can easily tell from the chart above, Mars Stations Retrograde approximately once every twenty-two to twenty-four months, transiting in retrograde motion for about 70 days. The in retrograde motion is an illusion of the planet moving backwards based on the placement of the planet in relation to the Earth and the Sun. When Mars is done transiting in retrograde motion, it will station briefly then resume the transit in direct motion.

To adjust the times for your timezone, add or subtract the number of hours your timezone is from 0 UT. If you live in the western hemisphere (mostly the Americas) you would subtract the number of hours from the time shown on the table. Most of the eastern hemisphere will add hours to the time shown in the table.

The planets sometimes speed up in their movements, slow down, stop and even reverse direction. The motion traces out a retrograde loop.
Rich Galaxy Cluster .

During a retrograde loop of Mars, would you expect Mars to be brighter than usual in the sky, about average in brightness, or fainter than usual in the sky? Explain.
33.

A further advantage of the heliocentric model is that the distances of the planets are specified by the sizes of their retrograde loops. A small retrograde loop means a large distance from the Sun.

I enjoy making quantitative measurements of the backward loops, and have measured the

s of each of the outer planets, with the exception of Neptune, several times over the last few years by taking star field photographs with a 50-mm lens on the camera, .

The figure below shows Mars'

(February 4 and April 29, 1997) are noted.

This path is often referred to as a "

This latter case is often referred to as a

. The shape of the retrograde motion depends on the position of the planet in its orbit. If the planet is near a node (the place in a planet's orbit where it crosses the ecliptic), then the retrograde motion is S-shaped.

The art above shows an actual

in the motion of the planet Mars. The inset above depicts the movements of several planets over the course of several years, as reproduced on the inside dome of a planetarium.

On Friday, March 9, the planet will cease its regular eastward motion in front of the distant stars and begin a

(red curve with dates) that will last until mid-July.

Ptolemy's modification of the previous, simpler Greek theory based on epicycles and deferents reproduced the apparent motions of the planets, including

s, so well that it remained unchallenged until the revival of the heliocentric theory by Nicholas Copernicus in the 16th century.