The Science of the Spherus Magna System

Hi everyone, this is my first post as a TTV member!

Over the past 2 years I have been slowly working on a scientific investigation of the Spherus Magna Planetary System from BIONICLE. Do you want to know the strength of the surface gravity on Bara Magna? The orbital distance of the Red Star? Take a look at the below links to find out the answers to these and way more questions you probably never asked. I’ve spent so long on this and poured so much time and effort into it and I am so proud of the result. I hope any of you that are interested will check it out - if you get even a tenth of the enjoyment out of it that I did making it, I think it will be time well spent.

I’ve got two versions of the document linked below, the summary version (which just contains my results without any of the workings out or maths behind it) and the full version (that contains all 53 pages of my full methodology):

Summary Paper

Full Paper

Here is a preview of some of my results - a fully to scale map of the system!

What do you think?

EDIT (24/08/2022) - Hi everyone - I have updated the links above with new and improved versions of my scientific study of BIONICLE - see the new links for the addition of information on the tides of Aqua Magna, alongside a much improved summary document that goes into the detail and differences of Greg canon vs Faber canon and contains a new page on some cool details that came about as a result of the study (including how Solis Magna moves across the sky in the opposite way to how the sun appears to move here on Earth, and the very strange view of the two moons the inhabitants of Bara Magna would see from the surface)



Sounds quite good…

(1) Welcome to the boards, mate
(2) hmmm, this seems about accurate. nice job

This is what I’ve always needed! Thanks for this, @RahiWatching ! This will really help on my stories!

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Gee, that’s a head-on serious scientific study. Great job!

Free fall acceleration of 14.5 m/s^2 is rough though, from biological perspective. And from perspective of constant flips, so loved by many Bionicle characters.

But for the evidence canon gave us, this is indeed great.

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Admittedly, I only looked at the Summary Paper, but I noticed one problem with the scaling. Canonically, the Great Spirit Robot is 40,000,000 feet tall-just shy of Earth’s diameter. But you have it portrayed as WAY smaller than the Earth.

Yes, that’s correct, however in the full paper I go into why the GSR here is not scaled at the 40 million feet size as per canon.

The short version is that if I used the canon scaling then the numbers arrived at for the rest of the system were absurdly large (Spherus Magna being several times larger than Jupiter!) so as part of my initial assumptions I used the smaller scale GSR as shown as part of the original concept art by Christian Faber.

Basically, my version of the system is an attempt to create a realistic version of the Spherus Magna system, compromising where needed with what is strictly “canon”.

To be honest, I probably should have put a bit more of that background into the summary paper, as it can be a bit confusing without the wider context


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This is some amazing work @RahiWatching !
This is exactly the kind of analysis I like. I enjoyed reading the paper.
However, I am still dissapointed that you chose not to go with the actual GSR size. I really wanted to know those real numbers and how ridiculously large they would be.
Would you consider a sequel detailing that process and having most of the equivalent results included?


Very interesting! I’ve been trying to do something similar with the Geography/Geology of Spherus Magna. Not so much the physics and mathematics, but creating a map of the planet as a whole, as well as what each body would look like after The Shattering. The trouble is, there’s not a lot of canon info about the specifics of Bota Magna, all we really know is that it’s in the northern part of the planet.


Sorry I took so long to respond, life has been majorly getting in the way in the last couple of months or so.

Some of the original calculations with the Greg Canon sizes GSR can be found already in appendix 3 of the main paper, though admittedly I only covered the diameters of the planets there and didn’t go into the detail of mass, gravity etc. I have some free time coming up in a couple of weeks and some more BIONICLE ideas that I want to science the heck out of, so I will see if I can get this one updated with the Greg Canon data too if I have the time.

So you don’t have to go looking for it, the Greg Canon diameters as per appendix 3 are as below:

Aqua / Bota Magna = 82,296km in diameter (for context, that’s significantly bigger than the the gas planet Uranus at 50,742km in diameter)

Bara / Spherus Magna = 246,888km in diameter (1.77 times the diameter of the gas planet Jupiter (139,820km in diameter), which is the largest planet in our solar system!)



Thanks for the response! If you do, that would be great :+1: I am genuinely interested in the updated version with the extra info.

I have tried some simple estimations on the surface gravity in the past based on some previous size measurements done by others, though I don’t have any background in astrophysics/astrogeology. One thing I came across as a roadblock was the average density of the planet. My calculations just assumed the density of the Earh (because of seemingly similar composition), but I knew that had to be underestimated. Surely a planet of that size would have higher density than Earth had it existed in that form (suspending the disbelief of a terrestrial planet that size). I just didn’t know how the density changes with incresing plantery diameter.
However, If I recall, you first determined the mass using a method I am not familiar with (but I assume is standard practice in astrophysics?), and then proceeded to calculate the density afterwards. So it would seem you do not need to know planet density first in order to determine its mass?

PS: Also there is one more thing I would be interested in (in both versions of your calculations) and that is the athmospheric pressure on the surface of the planet and some prediction of what gasses might make up the composition of the air in gasseous form.


I will see if I can get the time to make that update later this week.

Yes, I did use a different method to get the mass of Bara Magna, its a method that comes about as a result of Newton’s Laws of Gravitation and can be used in situations where you already know the orbital radius and orbital velocity of a moon orbiting the planet whose mass you are trying to measure (see footnote 14 on page 19 of the full paper for a link to a NASA site explaining more). I was lucky that through my assumptions about the system and my pixel measurements I had already calculated both of these measures, and so it meant that I could measure the mass of Bara Magna without needing to know its average density. Given I now had the mass and had also already calculated the volume of the planet, I could then work out the density from there, which came in handy in later calculations.

In terms of your last question, I did briefly consider if it would be possible to attempt to determine the characteristics of the atmospheres of the bodies in the Spherus Magna system, however I quickly rejected this. The mass, size, composition of planetary atmospheres is a very complex field of study and can be influenced by a whole host of factors, such as the composition of the original stellar cloud the planets formed from, the history of life and volcanism on the planet, strength of its magnetic field etc. – none of which there is any way to calculate from the evidence at hand from the BIONICLE storyline.

From what we do see in the storyline, we can make an educated guess that the atmosphere of Spherus Magna (and therefore the 3 bodies it split into) is roughly Earth-like in terms of temperature, pressure etc. Though it would likely have a higher oxygen content than the Earth’s atmosphere currently does, given the higher oxygen needs the large dinosaur-like creatures that exist on Bota Magna would have.



Thanks you for your explanation! I understand now how the mass came about.
Good point about the athmosphere, it would be no doubt much more complex than simply scaling up the earth-like conditions.
I’m looking forward to the update :+1:

Updates made! I hope you enjoy them. Be sure to check out both the new summary paper and the new full paper, improvements have been made to both!


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Great! I am going to read it today :+1: