Planetary memory structures

One of the most sophisticated and underrated memory systems uses planetary structures. It is not easy to learn, not very fast, but extremely powerful where all other methods fail. And it has a very cool historical background. What I explain in this article is not fully historically or mathematically accurate, but most details should be correct.

17th-century barbeques

One of the worst times in European history was the first half of the 17th century. Between religious wars, witch trials, hunger, and disease crossing the vast ocean to another continent might have been less dangerous than having an inquisitive mind. One of the people I can think of was Giordano Bruno. He used a very new heliocentric model of cosmology. And he used it to encode and memorize secret information that could not be written down. After a long trial, he was burned by the inquisition.

Bruno was not the only famous person combining science and philosophy.  Many traveling philosophers were really good astrologists. Paracelsus, the father of toxicology, used to combine astrology, chemistry, and medicine.  Kepler, the great astronomer of that era, used his mathematical skills for very accurate astrological predictions for the holy roman emperor Rudolf.

The thing to understand here: many educated people of that period knew astrology intimately well, as well as they knew Latin. So it is not a great surprise that astrological maps were used to encode important information and hide it from the inquisition.

Concentric circles

It does not matter if one used geocentric or heliocentric model, the planets used to circle around some big body. Like in a mindmap you can put your anchor marker in the center of the planetary memory structure. Do not try to be heroes and use elliptic orbits or nonequal placement of the planets in space.  The simpler the model, the easier the memorization. Heliocentric cosmology was Bruno’s innovation. We can use geocentric model with similar memorization accuracy.

Geocentric model

Each planet in astrology is associated with a specific color and qualities.

Notice that typically there are 7 planets around the central body, and each circle is usually divided into 12 sectors. The number of concentric circles may vary. Some say that our working memory has a length of 7 units of data.  Others may train themselves to use 9. Since Pluto is no longer a planet, 8 might be a good compromise.

12 sectors

The 12 signs of zodiacs are at least as old as Babylon. Some say that Babylonians used prior Egyptian or Sumerian knowledge. The 12 signs follow quite comfortable 12 months of the moon within one solar year. It is also an extremely good number as it is a multiple of 3 and 4. One can also easily count to 12 on phalanxes of fingers. The next more comfortable number is a multiple of 3, 4, and 5, namely 60.

The number of sectors per circle may change. In some places, the two inner circles had only 4 sectors, while the two outermost circles had 60 sectors. This was very comfortable for computations, as the accuracy of 1/60 is good enough for most engineering purposes. Circular sliding logarithmic rulers were used to compute things until the invention of computers.

Similarity to mindmaps

You can notice that the basic planetary structure is like a mindmap. There is one central circle, two circles with 4 branches corresponding to the first branching with 2 visualizations. Then there are 3 circles with 12 visualizations. And finally, there are two circles with 60 visualizations. Potentially you can encode 1+4*2+12*3+60*2 = 165 visualizations. Clearly, some visualizations can be left empty.

For some purposes, the radix of 8 is better. In this case, usually, the inner 4 circles have 8 sectors and the outer 3 circles have 24 sectors.  1+4*8+3*24=105 visualization.  For example, while European music has 12 notes per octave, Arabs have 24 notes per octave. The change looks small, yet the music is different. Typically 8 sector wheels are better for emotions.

If you move along the radial direction, it feels very much like a mindmap: from general to specific or from specific to general.

Similarity to the mental palace

The structure is fixed, and the itinerary can be either radial along the hierarchy or lateral along the circles of similar value. The lateral itinerary is very similar to a mental palace, as the location of the sector on the circle dictates its meaning, and the color is used to differentiate things contextually.

Also, this structure is extremely well built for placing PAOs. It is a mental palace you do not have to remember and can reuse as many times as you want.


You may keep the location of each circle fixed, or you may slide the circles. Sliding the circles generates new combinations and options we would not usually consider. It can be a powerful brainstorming tool.

The SCAMPER Technique is a team brainstorming technique used to develop or improve products or services. SCAMPER is an acronym for Substitute, Combine, Adapt, Modify/Magnify, Purpose, Eliminate/Minimize and Rearrange/Reverse. This generates 7 (or 10) sectors. The sectors do not have to be the same size: we prefer some operations to others.  Assign the parts of the system your work with and you get a lot of possibilities to play with.


The sectors can be used for emotions with various level of intentsity, using for example this model   with 8 sectors named Plutchic wheel. Plutchik also theorized twenty-four “Primary”, “Secondary”, and “Tertiary” dyads (feelings composed of two emotions). The wheel emotions can be paired in four groups:

Primary dyad = one petal apart = Love = Joy + Trust
Secondary dyad = two petals apart = Envy = Sadness + Anger
Tertiary dyad = three petals apart = Shame = Fear + Disgust
Opposite emotions = four petals apart = Anticipation + Surprise

You can use the specific combinations on the wheel to fine-tune your response. Read more about it here


“Circular sliding rulers” can be bought on aliexpress. They extremely effective for the conversion of unit systems. If you are more adventurous you can use logarithmic slider rulers or rulers for multiplication. More about it here. Notice that for computations, usually only the outer two circles are used, and 1/60 is considered to be sufficiently accurate.

Combining with other memory structures

Planetary memory structures do not work with other mental structures very well. We put them on floors and tables in the middle of rooms in mental palaces.  Alternatively, we may put them as leaves in mindmaps, including the mindmaps we may put on walls of mental palaces. The visualization should be massive and should be allowed its space. Otherwise it simply does not work very well.

When should we use planetary memory structures?

Clearly, the visualization can be used for navigation, astrology, and astronomy – as it was used in medieval times. In medieval times it was also used for computations and code-breaking like we use modern computers. For this part, I think it requires too much effort.

Yet I think the visualization is most useful with complex typological models. These models follow either a planetary structure or a simpler chessboard-like matrix structure. Both can be easily used for a wide range of activities.


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