Theory How does the Equestria Solar System look like?

[Quantum Pony 40]

Hi everypony

Throughout the years, I've read several interesting posts such as "How fast was Rainbow Dash when she achieved Sonic Rainboom" or "Comparing scales in MLP universe to our universe". So I thought it would be interesting to do a project on studying how the Equestria solar system would look like. I started this project a year ago but now I finally wrote it in a readable fashion (by which I mean in a way that hopefully makes some sense  ). I 'published' this paper here in picture form, but I also attached the original pdf file. Project_MLP.pdf.

I hope you guys enjoy it and please do let me know if something I wrote doesn't seem to make sense or is not clear  . Any form of feedback would be amazing and greatly appreciated . 

And let me know what are your thoughts on how the Equestria solar system should look like or any other thoughts you have on the role of Science in Equestria in general.

 

(pictures can be enlarged upon clicking and zooming in in a new window  )

 

(note: This is an updated version of a blog post on the same topic I did a year ago. Now that I looked back, there were a few (huge) mistakes there which I now corrected) 

 

 

Project_MLP.pdf

[SharpWit 2,648]

Equestria Potato Grant, I like that.

The only thing I have to add is that I personally think both the sun and moon would begin to orbit around the earth on their own in the Equestrian system, they just wouldn't line up on their own, creating harsh weather conditions that make life difficult but not impossible. It's done for the same reason the seasons have so much oversight, and weather is managed. I can't say for certain as a lack of evidence isn't evidence in of itself, but Equestria has most likely thwarted many weather based natural disasters like hurricanes, blizzards, flooding, and dust bowls, at least in heavily populated areas under their dominion.

[Quantum Pony 40]

2 hours ago, SharpWit said:

Equestria Potato Grant, I like that.

The only thing I have to add is that I personally think both the sun and moon would begin to orbit around the earth on their own in the Equestrian system, they just wouldn't line up on their own, creating harsh weather conditions that make life difficult but not impossible. It's done for the same reason the seasons have so much oversight, and weather is managed. I can't say for certain as a lack of evidence isn't evidence in of itself, but Equestria has most likely thwarted many weather based natural disasters like hurricanes, blizzards, flooding, and dust bowls, at least in heavily populated areas under their dominion.

That is a very nice point! I havn't really thought about the weather in this situation. 

For this article I only focused on the solar system after the interference of magic from unicorn/alicorns. But what you suggested could be a nice model before that. Without the interference of magic, the celestial objects would have crashed into each other unless they are in orbit. This could indeed explain the harsher weather condition in Equestria displayed in the show (before Celestia and Luna) and why the unicorns are willing to do every thing in their power to raise the sun, hence putting the celestial objects in a more orderly schedule. 

Thank you very much for the amazing input ! 

[BornAgainBrony 2,397]

9 hours ago, SharpWit said:

Equestria Potato Grant, I like that.

The only thing I have to add is that I personally think both the sun and moon would begin to orbit around the earth on their own in the Equestrian system, they just wouldn't line up on their own, creating harsh weather conditions that make life difficult but not impossible. It's done for the same reason the seasons have so much oversight, and weather is managed. I can't say for certain as a lack of evidence isn't evidence in of itself, but Equestria has most likely thwarted many weather based natural disasters like hurricanes, blizzards, flooding, and dust bowls, at least in heavily populated areas under their dominion.

Now I'm suddenly having this desire to plug the behavior of the sun/moon in Equestria into one of the major weather forecasting models that we currently use, to see what kind of patterns arise from it. I'm curious to know if realistically, it would create something incredibly stable, or incredibly chaotic. Over the course of a single day, if the distances from the planet didn't change, there shouldn't be much fluctuation in global patterns, right? Would Equestria's oceans even have tides?

[SharpWit 2,648]

1 hour ago, BornAgainBrony said:

Now I'm suddenly having this desire to plug the behavior of the sun/moon in Equestria into one of the major weather forecasting models that we currently use, to see what kind of patterns arise from it. I'm curious to know if realistically, it would create something incredibly stable, or incredibly chaotic. Over the course of a single day, if the distances from the planet didn't change, there shouldn't be much fluctuation in global patterns, right? Would Equestria's oceans even have tides?

You should see a high tide at the sun and moon's highest peak at the exact same time every day and night with little to no change in the tide's height.

One thing I'd really like to know, is what's the planet's angle, since it must be at a tilt to have seasons.

[Kadeda 178]

I believe that the planet of equestrian is mostly stationary. It doesn't spin but it still revolves around the sun. I think Equestria is just earth in the future due to similar resemblances of the land and what not. When Luna and Celestia move the sun and moon... they really do move the sun and moon. Celestia even mentioned how much easier it is to move the sun and moon so we know from that that we can assume the sun can be bigger, have a higher mass, be further away, or all of the above. 

It would take a while for the sun being moved to the wrong location to affect earth to badly. For example, if the sun disappeared right now... we wouldn't even know until 8 minutes passed. I think it's the same universe but for some reason... the earth stop rotating... and the moon doesn't revolve around the earth either. It's a recent problem... as in the early times of Equestria... this wasn't a problem or issue. It could have been effected by the science of magic.

My theory is with Equestria girls... is that they are going to the past. Why doesn't twilight going back in time affect her world? I think that's pretty easy to explain. If you think about now... there are things happening that can't be explained. Things that move faster than the speed of light... particles that only does anything when it's observed... or believe it's observed. There are a lot of mysteries out there. Equestria magic could be one of them.

Edited March 31, 2019 by Kadeda

[Quantum Pony 40]

On ‎3‎/‎31‎/‎2019 at 4:40 AM, Califorum said:

Moving the sun in moon is not how I imagine it.

Either there are 2 things, the planet goes around a sunlike star much like or solar system, or the sun and moon are the same size and go around the planet. If it is a geocentric system, it is artificial. Raising the sun and moon in my mind is not actually moving them, no, it's making an illusion. An illusion that, controls the heat and light, it may make the sun seem like it is there, but it's not. 

That is indeed a feasible model . In fact, this makes the distance between the sun and Equestria much more flexible, allowing the illusion of a very small sun very close to Equestria (just like Vegeta creating an artificial moon in Dragon ball Z ). However, it would be quite difficult for one pony to create a light source that emits enough energy to support all life on Equestria.  

 

19 hours ago, BornAgainBrony said:

Now I'm suddenly having this desire to plug the behavior of the sun/moon in Equestria into one of the major weather forecasting models that we currently use, to see what kind of patterns arise from it. I'm curious to know if realistically, it would create something incredibly stable, or incredibly chaotic. Over the course of a single day, if the distances from the planet didn't change, there shouldn't be much fluctuation in global patterns, right? Would Equestria's oceans even have tides?

That is very cool! !!! Given the 1380Wm^-2 luminosity for the Equestria sun in this model, I think temperature variation should be similar to Earth's model. So the only real difference would be the gravitational force exerted by the sun. And indeed, this most significantly affect the tides.

If we assume Equestria and Earth sun to have the same densities, the mass will vary 1/R^3 with radius R whereas, the gravitational force has a inverse square power law 1/d^2 for distance d. Keeping R/d constant, we have the force proportional to the radius R. Since a nearer sun is obviously smaller, the Equestria sun exerts a smaller gravitational force than Earth's sun. Since the gravitational force from Earth's sun is twice as weak as its moon, we can safely assume the Equestria sun is exerting a much weaker force than its moon.

However, Celestia did mention that it is easier to raise the moon than the sun, which should indicate the sun in heavier. In this case, the gravitational force from the sun would be stronger. 

Something I havn't really mentioned is the length of the lunar and solar cycles in this model. The solar cycle (being controlled by Celestia) should be the length of a day. I would argue the same for the lunar cycle (which also wasn't really specified in the show). And I think this is also what @SharpWit mentioned . 

Since on Earth, lunar cycles take around 28 days, the changes in tide in Equestria would be much more frequent (high and low tides on the same day). I think the simulation would yield (approximately) the same result as Earth having twin moons (and of course we need to include Earth's sun in the background but without turning on its gravitational field). 

Another interesting point is that we assumed Equestria doesnt rotate by itself. This means the absence of Coriolis force, which probably have tremendous effect on Equestria storm system.  

 

Edited March 31, 2019 by Quantum Pony

[RDDash 19,174]

I think I've heard it all. Canonically their planet is a sphere, so maybe it's just a tidaly locked?

[SilverComet 170]

The reason why moving the Equestrian Sun is "harder" is because of the distance.

Telekinesis strenght seems to "falloff" the same as any other force (farther objects require a higher energy output), plus the "feedback" of information on the applied surface [a facsimile of the tactile sense] will become more weak [akin to the "tower reception" of a cellphone], meaning an increased concentration to "pick up" the data and correct errors may also be needed on long distances.

The Equestrian Sun is likely to be much farther away than the minimum "+1 equestian lunar radius"; but at the same time both objects could be MUCH CLOSER (while being both much smaller), than the distance from Earth´s Moon to Earth.

The "absolute minimum" distance for the Equestrian Moon is the level of the outer atmosphere of Equestria [above to where the friction would become strong enough to both alterate its surface and produce shockwaves if moved at the speeds observed on S4E26]; but then we also had to take into account the "Paralax Problem" it could cause between cities on the surface of Equestria far away from each others [regardless if the PLANET of Equestria is a sphere (likely) or a plane, the "Nation" (observed "from space" in S4E26) represents only a fraction of its surface].

-> From Yakyakistan to Mt Aris, the Equestrian Sun does not seem to be too close to the horizon.

[Quantum Pony 40]

 

On ‎3‎/‎31‎/‎2019 at 11:54 AM, SharpWit said:

One thing I'd really like to know, is what's the planet's angle, since it must be at a tilt to have seasons.

That is a very interesting point. Since all four seasons were mentioned in the series, Equestria must experience them. I don’t see any elegant way this can arise from our model, so unfortunately we have to add some extra assumptions to make it work .

One of the arguments from traditional geocentric model is by tilting the axis of orbit of the sun instead to simulate the four seasons (however I must say I am not an expert on historical geocentric models ). 

(The Renaissance Mathematics, 2011)

The red circle represents the sun orbiting on the equatorial plane (although in our case this is arbitrary since Equestria does not actually rotate). The solar orbit in blue is tilted to some angle which introduces the variation of sunlight received by Earth throughout the year, hence producing the four seasons.

In our model, however, things are a bit more complicated since we insisted that the sun orbits around Equestria once per day. Yet, evidences from the series clearly shows the period of a season is much longer.

So here is what I propose. Let’s start at spring where the sun is at the ‘equatorial plane’ and both the northern hemisphere and southern hemisphere of Equestria receive the same amount of sunlight. As days gone by, Celestia slowly increases the tilt (ε) of the solar orbit until June where the northern hemisphere receives the most sunlight. Now, the tilt here is with respect to the equatorial plane but the orbit is different than depicted in the picture above. Here, we are actually raising the whole equatorial plane of orbit by an angle ε so the sun is no longer orbiting around the center of mass of Equestria. So we are not really tilting the orbit but raising the whole thing.

Celestia will continue to decrease the tilt until September where once again both hemisphere receives the same amount of sunlight. The tilt is decreased further below the original equatorial plane until winter solstice where the northern hemisphere receives the least amount of sunlight.

Quite taxing for Celestia to keep track of small variations every day, but I think this model might be able to simulate

the seasons we see in the series .

On ‎3‎/‎31‎/‎2019 at 3:30 PM, Kadeda said:

I believe that the planet of equestrian is mostly stationary. It doesn't spin but it still revolves around the sun. I think Equestria is just earth in the future due to similar resemblances of the land and what not. When Luna and Celestia move the sun and moon... they really do move the sun and moon. Celestia even mentioned how much easier it is to move the sun and moon so we know from that that we can assume the sun can be bigger, have a higher mass, be further away, or all of the above. 

It would take a while for the sun being moved to the wrong location to affect earth to badly. For example, if the sun disappeared right now... we wouldn't even know until 8 minutes passed. I think it's the same universe but for some reason... the earth stop rotating... and the moon doesn't revolve around the earth either. It's a recent problem... as in the early times of Equestria... this wasn't a problem or issue. It could have been effected by the science of magic.

I think that's a nice idea .  It could also explain the use of base ten when counting even though ponies technically only have one “finger”. Furthermore, most of the contraptions does seem out of place and inconvenient to be invented by ponies like using chalk/pen/quill/spoon with mouth.

On ‎3‎/‎31‎/‎2019 at 3:30 PM, Kadeda said:

My theory is with Equestria girls... is that they are going to the past. Why doesn't twilight going back in time affect her world? I think that's pretty easy to explain. If you think about now... there are things happening that can't be explained. Things that move faster than the speed of light... particles that only does anything when it's observed... or believe it's observed. There are a lot of mysteries out there. Equestria magic could be one of them.

For this case, and assuming the future Earth model, we can use the old time paradox arguments that you can never change the past and whatever you do in the past inevitably leads to the future. 

 

On ‎4‎/‎1‎/‎2019 at 5:36 AM, Califorum said:

No creation involved, merely manipulation of the light. Moving the sun and moon as physical objects is so ridiculous in my view.

I guess that could work. But I dare not go against will of Celestia. Just look at what happened to Ponileo Ponilei . 

 

Sorry for the late reply. Take a bit of time to look into detail the excellent points raised here . I'm still working on the response to the other posts . 

[SharpWit 2,648]

28 minutes ago, Quantum Pony said:

The red circle represents the sun orbiting on the equatorial plane (although in our case this is arbitrary since Equestria does not actually rotate). The solar orbit in blue is tilted to some angle which introduces the variation of sunlight received by Earth throughout the year, hence producing the four seasons.

In our model, however, things are a bit more complicated since we insisted that the sun orbits around Equestria once per day. Yet, evidences from the series clearly shows the period of a season is much longer.

So here is what I propose. Let’s start at spring where the sun is at the ‘equatorial plane’ and both the northern hemisphere and southern hemisphere of Equestria receive the same amount of sunlight. As days gone by, Celestia slowly increases the tilt (ε) of the solar orbit until June where the northern hemisphere receives the most sunlight. Now, the tilt here is with respect to the equatorial plane but the orbit is different than depicted in the picture above. Here, we are actually raising the whole equatorial plane of orbit by an angle ε so the sun is no longer orbiting around the center of mass of Equestria. So we are not really tilting the orbit but raising the whole thing.

Celestia will continue to decrease the tilt until September where once again both hemisphere receives the same amount of sunlight. The tilt is decreased further below the original equatorial plane until winter solstice where the northern hemisphere receives the least amount of sunlight.

Quite taxing for Celestia to keep track of small variations every day, but I think this model might be able to simulate

the seasons we see in the series .

Why doesn't Equestria rotate? Our sun rotates and has a tilt in it's axis, one that's smaller than the earth's but is present nonetheless, and this is despite being the center of our solar system. What's to say Equestria doesn't do the same? The difference here would be one rotation would be classified as a year rather than a day.

The biggest problem with this model is it requires orbiting satellites to be going much faster than the central body. I'm not certain, but I think this would result in Equestria's sun and moon being flung out of orbit, and perhaps this is the saving grace of having the royal sisters present to reign them back in.

[RDDash 19,174]

Keep in mind that our solar system is strange based on galactic standarts and it's all Jupiter's fault. The ponies maybe have two maybe three planets in their entire solar system. Some of them are Super Earth's some aren't, their star could be a giant or more than likely it could be a brown dwarf.

[Kadeda 178]

On 4/5/2019 at 11:01 AM, Quantum Pony said:

For this case, and assuming the future Earth model, we can use the old time paradox arguments that you can never change the past and whatever you do in the past inevitably leads to the future. 

It's already been an episode where time works exactly like that but the season five finale contradict it somewhat if not directly. It depends on the theory of time and if it's possible for multiple theories to be true. For example, maybe... only certain major events can lead to a change of the timeline like the sonic rain boom. There is also the idea that the season 5 finale just took place in alternate universes. At the same time, the argument that you can never change time can still be true as in these are events that happened way before the show happened and we only learn about it in season 5.

22 hours ago, R.D.Dash said:

Keep in mind that our solar system is strange based on galactic standarts and it's all Jupiter's fault. The ponies maybe have two maybe three planets in their entire solar system. Some of them are Super Earth's some aren't, their star could be a giant or more than likely it could be a brown dwarf.

Yeah, Jupiter messed our whole solar system up. Equestria (dunno name of planet) could even be a super earth... if it's not earth itself in the future.

Edited April 6, 2019 by Kadeda

[Quantum Pony 40]

On 4/1/2019 at 6:10 AM, R.D.Dash said:

I think I've heard it all. Canonically their planet is a sphere, so maybe it's just a tidaly locked?

Yup, that could work and it would explain why we always see the same face of the moon (like the 'mare in the moon' back in season 1  ). But if we were to assume Celestia raises and moves the sun, then we can't really have Equestria rotating. Now, if only the moon rotates, there will be a net transfer of rotational energy to Equestria, causing it to rotate about its own axis as well. Which isn't really what we want...

But if the rotation of Equestria is very slow (which is likely since the moon is much smaller, making it difficult to move the much larger Equestria), then it probably wouldn't affect Celestia raising and lowering the sun (for example one rotation might be as long as 100 'days') and indeed Equestria would be tidal locked to the moon. 

On 4/4/2019 at 12:29 AM, SilverComet said:

Telekinesis strenght seems to "falloff" the same as any other force (farther objects require a higher energy output), plus the "feedback" of information on the applied surface [a facsimile of the tactile sense] will become more weak [akin to the "tower reception" of a cellphone], meaning an increased concentration to "pick up" the data and correct errors may also be needed on long distances.

Yup I absolutely agree with this point. I would also argue that since magic is clearly a long distance force, its strength will fall off following the inverse square law: F_magic is proportional to (1/d^2) where (d is the distance between the magic user and the object) just like gravity. 

On 4/4/2019 at 12:29 AM, SilverComet said:

The reason why moving the Equestrian Sun is "harder" is because of the distance.

On 4/4/2019 at 12:29 AM, SilverComet said:

The Equestrian Sun is likely to be much farther away than the minimum "+1 equestian lunar radius"

One can also argue that if magic behaves like the other forces, it would require a greater amount of force to move a heavier object. So indeed, a further sun would be more difficult to move, but so would a denser and heavier sun that is closer. The issue with a sun much further away is that it takes too long for magic to reach it (assuming it does not travel faster than the speed of light). So we can't really have Celestia 'instantly' moving the sun with her magic as it will take a few minutes for her magic to reach the sun and for the light from the sun to return to Equestria. So ponies of Equestria would see a much delayed effect.  

On 4/4/2019 at 12:29 AM, SilverComet said:

but at the same time both objects could be MUCH CLOSER (while being both much smaller), than the distance from Earth´s Moon to Earth.

If this is the case then I do agree with the statement above since the delay for both raising the sun and the moon would be minuscule. In fact, if we loosen up some of the assumptions (like Equestria lunar distance is the same as Earth lunar distance) then quite a few other variables can be more flexible as well such as the size of the sun compared to the moon. However, if we depart from the model in our universe too much, it could have a lot of unwanted variations (like what you highlighted in the last two paragraphs when they are too close to Equestria). So I think you are absolutely right but I guess the Equestria-Moon distance = Earth-Moon distance is a choice and convention I decided to take in this article   as to stay as close as possible to the model in our universe. 

On 4/4/2019 at 12:29 AM, SilverComet said:

The "absolute minimum" distance for the Equestrian Moon is the level of the outer atmosphere of Equestria [above to where the friction would become strong enough to both alterate its surface and produce shockwaves if moved at the speeds observed on S4E26]; but then we also had to take into account the "Paralax Problem" it could cause between cities on the surface of Equestria far away from each others [regardless if the PLANET of Equestria is a sphere (likely) or a plane, the "Nation" (observed "from space" in S4E26) represents only a fraction of its surface].

-> From Yakyakistan to Mt Aris, the Equestrian Sun does not seem to be too close to the horizon.

Wow that is quite a detailed analysis!  . I havn't really thought about the minimum distance but I absolutely agree with your analysis here. And it does seem like if it is too low in altitude, you wouldn't see a sun 'high above' at certain latitudes. Thank you for your detailed analysis!

 

On 4/5/2019 at 11:53 PM, SharpWit said:

Why doesn't Equestria rotate? Our sun rotates and has a tilt in it's axis, one that's smaller than the earth's but is present nonetheless, and this is despite being the center of our solar system. What's to say Equestria doesn't do the same? The difference here would be one rotation would be classified as a year rather than a day.

The biggest problem with this model is it requires orbiting satellites to be going much faster than the central body. I'm not certain, but I think this would result in Equestria's sun and moon being flung out of orbit, and perhaps this is the saving grace of having the royal sisters present to reign them back in.

Hmm,that does seem to work. And as long as Equestria's rotation is slow enough, the duty of bringing force days and night still falls mainly on the two sisters. If it does take say 365 'days' for Equestria to rotate once, the difference in a length of a day would be negligible compared to the model where Earth doesn't rotate. Although I am not sure if it will bring the seasons though... I need to think about this a bit more . But yeah I agree that it could rotate and if it does bring the seasons, it will be a much more elegant model than what I was proposing in the previous reply   . And it makes it easier to define a year as well ! 

[Dreamstar Moonlight 44]

@Quantum Pony

WOW!!! Just....WOW!!!

This was such a fantastic read! Out of all the theories I’ve researched so far, yours seem to be the most consistent, simple and ...quite literally, the BEST!

But I have several questions, which I hope you might help me out with. But before that, I must get some other stuff out of the way – things other people have asked you about, but your answers may have been...slightly off the mark.

You concluded your report with the following paragraph

“In our model of the Equestria solar system, the position of the sun is chosen to be dEquestria sun = dmoon + Rmoon so that it is near enough to react almost instantly to  Celestia's magic but still further away than the moon. ......Furthermore, the sun, moon and Equestria are station- any relative to each other rather than orbiting around themselves. As a result, Celestia and Luna constantly use their magic to reposition the sun and the moon to bring forth day and night in Equestria.”

 

Here you raise some queries, which I’m hoping I could give my two cents on, before moving on to my questions:

 

(a)   “Firstly, for a star to be the same size of our moon is unheard of in our universe. Secondly, we assumed the temperature of the Equestria sun to be the same as ours which is quite concerning (since it needs to be at a certain size to sustain the fusion reactions in its core in order to generate heat).”

 

Don’t think too deeply into it. In a world of magic, the sun being the same size as the moon and yet being able to sustain the fusion reactions in its core can be attributed to some unknown magical force we know nothing about.

 

(b)   “There is also the question about whether Equestria is flat or spherical.”

 

I think I can answer that for you. In the season 9 episode 4 Sparkle’s Seven, Pinkie Pie daydreams about going into space. You can see quite clearly taht whatever planet Equestria is on, is spherical – just like our earth. Just pause the video at the 0:55 mark. Link: https://www.youtube.com/watch?v=K55MwoICwlQ&list=PLx1QWYCXgu5l6fsbN3NwaskH8m88mf_8E&index=3

 

Now moving on to the other questions other people raised, and which you’d replied to, but you might have missed out certain points, which I’d like to draw your attention to.

1.      On 3/31/2019 at 7:16 AM, BornAgainBrony said:

“.........Would Equestria's oceans even have tides?”

And you replied:

“You should see a high tide at the sun and moon's highest peak at the exact same time every day and night with little to no change in the tide's height.”

On the contrary, there is a slight indication that that is not the case. In the picture storybook Under the Sparkling Sea, the invitations states that the Annual Aquastria Race will officially begin after the First Moon Tide, implying that tides don’t occur on a daily basis, like you theorized. Before you dismiss this as non-canon, elements from this particular storybook have been alluded to in the IDW comics, which are B-canon, so I’m inclined to treat this as canon for all it’s worth.

2.      On 4/1/2019 at 3:40 AM, R.D.Dash said:

“...Canonically their planet is a sphere, so maybe it's just a tidaly locked?”

And you replied:

“Yup, that could work and it would explain why we always see the same face of the moon (like the 'mare in the moon' back in season 1  ). But if we were to assume Celestia raises and moves the sun, then we can't really have Equestria rotating....... But if the rotation of Equestria is very slow (which is likely since the moon is much smaller, making it difficult to move the much larger Equestria), then it probably wouldn't affect Celestia raising and lowering the sun (for example one rotation might be as long as 100 'days') and indeed Equestria would be tidal locked to the moon.”

Except that we do see other phases of the moon. Luna’s cutie-mark is a crescent, indicating that that particular phase is present. Furthermore, in the IDW’s “Reflections” arc (Issues 17-20), Princess Luna wonders whether the moon is a “waxing crescent” or a “waning gibbons”, further strengthening the theory that moon phases do indeed exist in Equestria.

And finally, the most important point:

3.      On 4/5/2019 at 9:23 PM, SharpWit said:

“Why doesn't Equestria rotate? Our sun rotates and has a tilt in it's axis, one that's smaller than the earth's but is present nonetheless, and this is despite being the center of our solar system. What's to say Equestria doesn't do the same? The difference here would be one rotation would be classified as a year rather than a day.

The biggest problem with this model is it requires orbiting satellites to be going much faster than the central body. I'm not certain, but I think this would result in Equestria's sun and moon being flung out of orbit, and perhaps this is the saving grace of having the royal sisters present to reign them back in.”

And you replied,

“Hmm,that does seem to work. And as long as Equestria's rotation is slow enough, the duty of bringing force days and night still falls mainly on the two sisters. If it does take say 365 'days' for Equestria to rotate once, the difference in a length of a day would be negligible compared to the model where Earth doesn't rotate. Although I am not sure if it will bring the seasons though... I need to think about this a bit more. But yeah I agree that it could rotate and if it does bring the seasons, it will be a much more elegant model than what I was proposing in the previous reply. And it makes it easier to define a year as well! 

This.

This right here is what I was looking for.

You see, a group of people, including myself re putting together a rather exhaustive chronology of events – basically, a complete timeline taking into account not only the episodes, but also all the comic books, chapter books, mangas, picture storybooks – you name it. So far, we’ve managed quite well. But there’s one particularly crucial fact that, if we get wrong, could be disastrous. And that is,

How long is a ‘moon’?

So far we’ve come up with several values:

·         1 moon = 1 lunar cycle = 27.3-29.5 days

·         1 moon = 3.42 days (https://mlp.fandom.com/wiki/User_blog:RiceWaffleFox/How_long_is_a_%22moon,%22_anyways%3F)

·         1 moon = 7 days or 14 days

All of these values are determined considering the fact that Equestrai must have a lunar cycle. And tides. And seasonal changes.

For our chronology, we’ve decided that:

·         Spring begins on the spring equinox ( 20 March)

·         Summer begins on the summer solstice ( 21 June)

·         Fall (autumn) begins on the Fall equinox ( 23 September)

·         Winter begins on the winter solstice ( 22 December)

So, you see, there must be years and months. Preferably a year that has 365 days, just like ours.

And lastly, does Equestria have a geocentric or a heliocentric solar system? What do you think about this? Link: https://www.deviantart.com/ahsokafan100/art/Equestria-Solar-System-618591164

Everything should fall into place if your theory could somehow explain these facts. I humly ask you this – could you please provide us with an answer? Somehow? It would be tremendously helpful! You have no idea how immensely grateful we would be!!

Hoping for a positive response!

-          Dreamstar Moonlight

[Tom Gallagher 33,588]

More importantly, how do I get to it? 

[Splashee 28,564]

I feel Equestria might be flat, and the sun and the moon are objects in the sky, movable by magic. The stars are just paintings in the background

[Dreamstar Moonlight 44]

6 hours ago, Splashee® said:

I feel Equestria might be flat, and the sun and the moon are objects in the sky, movable by magic. The stars are just paintings in the background

Now we know that is canonically untrue, because :

1) In season 2 episode "Heaerh's Warming Eve", Pinkie Pie (who portrays Chancellor Puddinghead) tells Applejack (who portrays Smart Cookie) expicitly taht "the earth is round; there's no up or down".

2) Also, In the season 9 episode 4 Sparkle’s Seven, Pinkie Pie daydreams about going into space. You can see quite clearly taht whatever planet Equestria is on, is spherical – just like our earth.

[Dreamstar Moonlight 44]

10 hours ago, TomDaBombMLP said:

More importantly, how do I get to it? 

How do you get what, exactly?

 

[Tom Gallagher 33,588]

1 minute ago, Dreamstar Moonlight said:

How do you get what, exactly?

 

To the Equestrian Solar System! (I was only joking.)

[Dreamstar Moonlight 44]

On 9/9/2020 at 9:06 PM, Dreamstar Moonlight said:

@Quantum Pony

WOW!!! Just....WOW!!!

 

This was such a fantastic read! Out of all the theories I’ve researched so far, yours seem to be the most consistent, simple and ...quite literally, the BEST!

 

But I have several questions, which I hope you might help me out with. But before that, I must get some other stuff out of the way – things other people have asked you about, but your answers may have been...slightly off the mark.

 

You concluded your report with the following paragraph

 

“In our model of the Equestria solar system, the position of the sun is chosen to be dEquestria sun = dmoon + Rmoon so that it is near enough to react almost instantly to  Celestia's magic but still further away than the moon. ......Furthermore, the sun, moon and Equestria are station- any relative to each other rather than orbiting around themselves. As a result, Celestia and Luna constantly use their magic to reposition the sun and the moon to bring forth day and night in Equestria.”

 

 

 

Here you raise some queries, which I’m hoping I could give my two cents on, before moving on to my questions:

 

 

 

(a)   “Firstly, for a star to be the same size of our moon is unheard of in our universe. Secondly, we assumed the temperature of the Equestria sun to be the same as ours which is quite concerning (since it needs to be at a certain size to sustain the fusion reactions in its core in order to generate heat).”

 

 

 

Don’t think too deeply into it. In a world of magic, the sun being the same size as the moon and yet being able to sustain the fusion reactions in its core can be attributed to some unknown magical force we know nothing about.

 

 

 

(b)   “There is also the question about whether Equestria is flat or spherical.”

 

 

 

I think I can answer that for you. In the season 9 episode 4 Sparkle’s Seven, Pinkie Pie daydreams about going into space. You can see quite clearly taht whatever planet Equestria is on, is spherical – just like our earth. Just pause the video at the 0:55 mark. Link: https://www.youtube.com/watch?v=K55MwoICwlQ&list=PLx1QWYCXgu5l6fsbN3NwaskH8m88mf_8E&index=3

 

 

 

Now moving on to the other questions other people raised, and which you’d replied to, but you might have missed out certain points, which I’d like to draw your attention to.

 

1.      On 3/31/2019 at 7:16 AM, BornAgainBrony said:

 

“.........Would Equestria's oceans even have tides?”

And you replied:

 

“You should see a high tide at the sun and moon's highest peak at the exact same time every day and night with little to no change in the tide's height.”

On the contrary, there is a slight indication that that is not the case. In the picture storybook Under the Sparkling Sea, the invitations states that the Annual Aquastria Race will officially begin after the First Moon Tide, implying that tides don’t occur on a daily basis, like you theorized. Before you dismiss this as non-canon, elements from this particular storybook have been alluded to in the IDW comics, which are B-canon, so I’m inclined to treat this as canon for all it’s worth.

 

2.      On 4/1/2019 at 3:40 AM, R.D.Dash said:

 

“...Canonically their planet is a sphere, so maybe it's just a tidaly locked?”

And you replied:

 

“Yup, that could work and it would explain why we always see the same face of the moon (like the 'mare in the moon' back in season 1  ). But if we were to assume Celestia raises and moves the sun, then we can't really have Equestria rotating....... But if the rotation of Equestria is very slow (which is likely since the moon is much smaller, making it difficult to move the much larger Equestria), then it probably wouldn't affect Celestia raising and lowering the sun (for example one rotation might be as long as 100 'days') and indeed Equestria would be tidal locked to the moon.”

 

Except that we do see other phases of the moon. Luna’s cutie-mark is a crescent, indicating that that particular phase is present. Furthermore, in the IDW’s “Reflections” arc (Issues 17-20), Princess Luna wonders whether the moon is a “waxing crescent” or a “waning gibbons”, further strengthening the theory that moon phases do indeed exist in Equestria.

 

And finally, the most important point:

 

3.      On 4/5/2019 at 9:23 PM, SharpWit said:

 

“Why doesn't Equestria rotate? Our sun rotates and has a tilt in it's axis, one that's smaller than the earth's but is present nonetheless, and this is despite being the center of our solar system. What's to say Equestria doesn't do the same? The difference here would be one rotation would be classified as a year rather than a day.

 

The biggest problem with this model is it requires orbiting satellites to be going much faster than the central body. I'm not certain, but I think this would result in Equestria's sun and moon being flung out of orbit, and perhaps this is the saving grace of having the royal sisters present to reign them back in.”

 

And you replied,

 

“Hmm,that does seem to work. And as long as Equestria's rotation is slow enough, the duty of bringing force days and night still falls mainly on the two sisters. If it does take say 365 'days' for Equestria to rotate once, the difference in a length of a day would be negligible compared to the model where Earth doesn't rotate. Although I am not sure if it will bring the seasons though... I need to think about this a bit more. But yeah I agree that it could rotate and if it does bring the seasons, it will be a much more elegant model than what I was proposing in the previous reply. And it makes it easier to define a year as well! 

 

This.

 

This right here is what I was looking for.

 

You see, a group of people, including myself re putting together a rather exhaustive chronology of events – basically, a complete timeline taking into account not only the episodes, but also all the comic books, chapter books, mangas, picture storybooks – you name it. So far, we’ve managed quite well. But there’s one particularly crucial fact that, if we get wrong, could be disastrous. And that is,

 

How long is a ‘moon’?

 

So far we’ve come up with several values:

 

·         1 moon = 1 lunar cycle = 27.3-29.5 days

 

·         1 moon = 3.42 days (https://mlp.fandom.com/wiki/User_blog:RiceWaffleFox/How_long_is_a_%22moon,%22_anyways%3F)

 

·         1 moon = 7 days or 14 days

 

All of these values are determined considering the fact that Equestrai must have a lunar cycle. And tides. And seasonal changes.

 

For our chronology, we’ve decided that:

 

·         Spring begins on the spring equinox ( 20 March)

 

·         Summer begins on the summer solstice ( 21 June)

 

·         Fall (autumn) begins on the Fall equinox ( 23 September)

 

·         Winter begins on the winter solstice ( 22 December)

 

So, you see, there must be years and months. Preferably a year that has 365 days, just like ours.

 

And lastly, does Equestria have a geocentric or a heliocentric solar system? What do you think about this? Link: https://www.deviantart.com/ahsokafan100/art/Equestria-Solar-System-618591164

 

Everything should fall into place if your theory could somehow explain these facts. I humly ask you this – could you please provide us with an answer? Somehow? It would be tremendously helpful! You have no idea how immensely grateful we would be!!

 

Hoping for a positive response!

 

-          Dreamstar Moonlight

 

@Quantum Pony

Also, I was wondering if the following thread will be helpful to you in any way:

There's a ton of scientific stuff in there, most of which rolled over my head like water off a duck's back. But I'd suggest you give it a read!

 

[Quantum Pony 40]

Hi @Dreamstar Moonlight Thank you so much for the detailed comment!!! I am really glad you liked it! 

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

a)   “Firstly, for a star to be the same size of our moon is unheard of in our universe. Secondly, we assumed the temperature of the Equestria sun to be the same as ours which is quite concerning (since it needs to be at a certain size to sustain the fusion reactions in its core in order to generate heat).”

Don’t think too deeply into it. In a world of magic, the sun being the same size as the moon and yet being able to sustain the fusion reactions in its core can be attributed to some unknown magical force we know nothing about.

Yes! You are absolutely right! By classifying magic as a fundamental force of nature, it is very likely that the values of certain fundamental constants of the Equestria universe will be different than ours. And since whether or not a fusion reaction occurs heavily depends on these constants, it is not impossible to happen with a much lighter star. 

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

(b)   “There is also the question about whether Equestria is flat or spherical.”

I think I can answer that for you. In the season 9 episode 4 Sparkle’s Seven, Pinkie Pie daydreams about going into space. You can see quite clearly taht whatever planet Equestria is on, is spherical – just like our earth. Just pause the video at the 0:55 mark. Link: https://www.youtube.com/watch?v=K55MwoICwlQ&list=PLx1QWYCXgu5l6fsbN3NwaskH8m88mf_8E&index=3

This is absolutely beautiful! This scene settles the question of flat vs spherical earth once and for all!

So, in a the Hearth's Warming eve episode, Pinkie (Chancellor Puddinghead) remarked that the world is round, but that didn't really settle the question as Equestria can be disk shaped or spherical. But the video you linked shows the image of (what seems like) Saturn's ring going around it. So indeed! it looks like Equestria IS spherical (which makes the computations above much easier to perform). 

 

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

1.      On 3/31/2019 at 7:16 AM, BornAgainBrony said:

“.........Would Equestria's oceans even have tides?”

And you replied:

“You should see a high tide at the sun and moon's highest peak at the exact same time every day and night with little to no change in the tide's height.”

On the contrary, there is a slight indication that that is not the case. In the picture storybook Under the Sparkling Sea, the invitations states that the Annual Aquastria Race will officially begin after the First Moon Tide, implying that tides don’t occur on a daily basis, like you theorized. Before you dismiss this as non-canon, elements from this particular storybook have been alluded to in the IDW comics, which are B-canon, so I’m inclined to treat this as canon for all it’s worth.

Ohh I see, indeed then the tides will follow similar pattern as Earth's tides. So far I am constraining myself to the MLP universe from the episodes, but including the IDW comics will be really interesting and enriches what we can say about the structure of the universe. There are some very interesting things in IDW comics from parallel universes to time traveling Observers that one can explore.

 

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

2.      On 4/1/2019 at 3:40 AM, R.D.Dash said:

“...Canonically their planet is a sphere, so maybe it's just a tidaly locked?”

And you replied:

“Yup, that could work and it would explain why we always see the same face of the moon (like the 'mare in the moon' back in season 1  ). But if we were to assume Celestia raises and moves the sun, then we can't really have Equestria rotating....... But if the rotation of Equestria is very slow (which is likely since the moon is much smaller, making it difficult to move the much larger Equestria), then it probably wouldn't affect Celestia raising and lowering the sun (for example one rotation might be as long as 100 'days') and indeed Equestria would be tidal locked to the moon.”

Except that we do see other phases of the moon. Luna’s cutie-mark is a crescent, indicating that that particular phase is present. Furthermore, in the IDW’s “Reflections” arc (Issues 17-20), Princess Luna wonders whether the moon is a “waxing crescent” or a “waning gibbons”, further strengthening the theory that moon phases do indeed exist in Equestria.

So here I'd argue that  just like how Earth's moon have different phases despite being tidally locked, Equestria's moon can have different phases too. However, since we do not see the 'dark side of the Equestria moon' I would argue they are tidally locked. This would in fact lead to a situation where Equestria experiences all the different phases from waning crescent to waning gibbons in a single day  .

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

There's a ton of scientific stuff in there, most of which rolled over my head like water off a duck's back. But I'd suggest you give it a read!

Ahh! This looks very interesting. I will take a closer look at this and perhaps it will give me a different view on how tidal locking works in Equestria. Thanks for the link!! 

 

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

And lastly, does Equestria have a geocentric or a heliocentric solar system? What do you think about this? Link: https://www.deviantart.com/ahsokafan100/art/Equestria-Solar-System-618591164

So based on the model here I'd say it is geocentric. Although now that I think about it, it is possible that whenever Celestia 'moves' the sun, one can imagine the Sun being the massive object in the centre of the solar system and Celestia uses it as a pivot to move the Earth around it. But this would mean Celestia wasnt really upfront with 'moving the sun' bit for the last thousand moons  . 

On 9/10/2020 at 5:08 PM, Dreamstar Moonlight said:

This.

This right here is what I was looking for.

You see, a group of people, including myself re putting together a rather exhaustive chronology of events – basically, a complete timeline taking into account not only the episodes, but also all the comic books, chapter books, mangas, picture storybooks – you name it. So far, we’ve managed quite well. But there’s one particularly crucial fact that, if we get wrong, could be disastrous. And that is,

How long is a ‘moon’?

This is a very interesting question!

Following the model here one might be eager to say that a 'moon' is a single day. However, that clearly contradicts many evidences in the show. For example, a thousand moons would then only be a few years. If that is true,  Twilight and her friends would have seen the reign of the two sisters when they were younger... So this puts a lower boundary (of a day) on what a moon can be. 

On the other hand, a moon can't be too long either, since Equestria portal opens once every 30 moons, so its probably not on the same scale as a year. This puts your predictions of 7 to 29 days nicely within the boundary. It is likely that 'a moon' and 'a year' is not trivially defined by the orbit of Sun and Moon around Earth.  I will need to do some more thorough research on this before getting back to you .                       

   Having a chronology of events that includes all MLP related material is an enormous and amazing task! It requires an abundant knowledge of the show's material and from your responses above I'd say you definitely have such knowledge!  I would love to see it when it's completed!  

(p.s: Would the timeline also cover events happening in parallel universes too? It will probably be just a branch off the main timeline, but some of them (like the opposite/mirror universe) does deviate from the main timeline quite early in Equestria history . )

Thank you for your detailed response! I will think about the length of a moon some more and get back to you  !

 

[O-78 28,606]

I created my own headcanon for the Equestrian system not too long ago. I made it similar to our system, but with some notable differences. The first 6 planets are mostly based on the ones in the image that @Scar posted, with a couple of changes. I then added 6 other planets that are more distant and were not known to the ancient Equestrians, for a total of 12 planets.

They're in the spoiler below if you're interested.

Spoiler

The Sun

A yellow G4V star, similar in size to our Sun. Princess Celestia does not raise it, that is just illusionary magic.

 

Inner (Terrestrial) Planets:

 

1. Ultus

A small, scorched Mercury-like planet orbiting extremely close to the Sun.

Moons: none

 

2. Jalis

Another Mercury-like planet close to the sun. It is slightly larger than Ultus.

Moons: none

 

3. Kovestum

A hot and heavily cratered planet, similar in size to Mars.

Moons: 2

 

4. Renaia

The Earth-like world where Equestria is located. It is the only planet in this system to support life. Princess Luna does not raise its moon, that is just illusionary magic.

Moons: 1

 

5. Wistrol

A large rocky planet, about twice the size of Renaia, with a hazy atmosphere and a prominent ring system.

Moons: 5

 

Outer (Giant) Planets:

 

6. Doukall

A massive super-Jovian gas giant that is four times as massive as all other planets in the system combined. It was the most distant planet known to the ancient Equestrians.

Moons: 57

 

7. Merlanos

An acid green gas giant, slightly smaller than Saturn, with a highly prominent ring system.

Moons: 39

 

 

8. Ferlatta

A white ice giant with a faint ring system, the most distant planet visible to the naked eye from Renaia.

Moons: 17

 

9. Olyria

A bright blue ice giant with a highly prominent ring system. It is the largest of the ice giants.

Moons: 23

 

10. Seforia

A deep purple ice giant with no visible ring system. It is the smallest of the ice giants.

Moons: 14

 

Distant Planets:

 

11. Axtum

A frozen Mars-sized planet three times as far from the sun as Seforia, traveling in a highly eccentric elliptical orbit.

Moons: 2

 

12. Zylonda

A dark ice giant orbiting at the furthest edge of the system. Its gravitational effects distort Axtum’s orbit.

Number of moons unknown

 

Edited October 17, 2020 by LyraLover 💚

[Dreamstar Moonlight 44]

23 hours ago, Quantum Pony said:

Hi @Dreamstar Moonlight Thank you so much for the detailed comment!!! I am really glad you liked it! 

Yes! You are absolutely right! By classifying magic as a fundamental force of nature, it is very likely that the values of certain fundamental constants of the Equestria universe will be different than ours. And since whether or not a fusion reaction occurs heavily depends on these constants, it is not impossible to happen with a much lighter star. 

This is absolutely beautiful! This scene settles the question of flat vs spherical earth once and for all!

So, in a the Hearth's Warming eve episode, Pinkie (Chancellor Puddinghead) remarked that the world is round, but that didn't really settle the question as Equestria can be disk shaped or spherical. But the video you linked shows the image of (what seems like) Saturn's ring going around it. So indeed! it looks like Equestria IS spherical (which makes the computations above much easier to perform). 

 

Ohh I see, indeed then the tides will follow similar pattern as Earth's tides. So far I am constraining myself to the MLP universe from the episodes, but including the IDW comics will be really interesting and enriches what we can say about the structure of the universe. There are some very interesting things in IDW comics from parallel universes to time traveling Observers that one can explore.

 

So here I'd argue that  just like how Earth's moon have different phases despite being tidally locked, Equestria's moon can have different phases too. However, since we do not see the 'dark side of the Equestria moon' I would argue they are tidally locked. This would in fact lead to a situation where Equestria experiences all the different phases from waning crescent to waning gibbons in a single day  .

Ahh! This looks very interesting. I will take a closer look at this and perhaps it will give me a different view on how tidal locking works in Equestria. Thanks for the link!! 

 

So based on the model here I'd say it is geocentric. Although now that I think about it, it is possible that whenever Celestia 'moves' the sun, one can imagine the Sun being the massive object in the centre of the solar system and Celestia uses it as a pivot to move the Earth around it. But this would mean Celestia wasnt really upfront with 'moving the sun' bit for the last thousand moons  . 

This is a very interesting question!

Following the model here one might be eager to say that a 'moon' is a single day. However, that clearly contradicts many evidences in the show. For example, a thousand moons would then only be a few years. If that is true,  Twilight and her friends would have seen the reign of the two sisters when they were younger... So this puts a lower boundary (of a day) on what a moon can be. 

On the other hand, a moon can't be too long either, since Equestria portal opens once every 30 moons, so its probably not on the same scale as a year. This puts your predictions of 7 to 29 days nicely within the boundary. It is likely that 'a moon' and 'a year' is not trivially defined by the orbit of Sun and Moon around Earth.  I will need to do some more thorough research on this before getting back to you .                       

   Having a chronology of events that includes all MLP related material is an enormous and amazing task! It requires an abundant knowledge of the show's material and from your responses above I'd say you definitely have such knowledge!  I would love to see it when it's completed!  

(p.s: Would the timeline also cover events happening in parallel universes too? It will probably be just a branch off the main timeline, but some of them (like the opposite/mirror universe) does deviate from the main timeline quite early in Equestria history . )

Thank you for your detailed response! I will think about the length of a moon some more and get back to you  !

 

@Quantum Pony

Thank you for your comment!

And I'm so happy that you agreed to most of my points! As for the Equestrian moon going through all of the phases in a single day – I don’t think that particular fact would really affect my chronology in any particular way, so I’d be happy to agree with you on that point.

Here's another thing I think I can clarify for you.  The Equestrian solar system is indeed geocentric, and this image from Part 2 of the season 4 premiere proves it!

 

(I only found this image after I posted my original comment – barely a couple of days ago). So that’s another point we can both agree on.

Going to the subject of ‘moons’ (the unit of time) – that’s a very tiresome topic because it can be anything from (approximately)  3 days to a week or even 27-29 days (but less than a month), depending on the story. Jayson Thiessen went on record saying that a ‘moon’ has ‘no human equivalent’ [source: https://mlp.fandom.com/wiki/Moons ], so I don’t think it would be possible to pin down an exact value. However, if you do manage to come up with a plausible theory (however far-fetched it may seem to you) that can explain how ponies define a ‘moon’ (preferably 1 moon = 3.42 days or 7 days – I’ll explain the reason in my final project), I would be delighted to hear it!

As for your question,

“Would the timeline also cover events happening in parallel universes too? It will probably be just a branch off the main timeline, but some of them (like the opposite/mirror universe) does deviate from the main timeline quite early in Equestria history.”

The answer is ‘Yes!”. And although at first glance, it may seem that the mirror universe deviates from the main timeline continuity; in actuality, it does not!

You may be surprised, but if you probe deeper into the storylines, you’d notice that there’s a lot of ‘ambiguity’ involved, and my friends and I, with the help of other fans have come up with explanations that tie together everything as well as can be expected, while staying as closely as possible to the canon material. I apologise if I sound vague, but attempting to explain all of this would take me another couple of pages! You’ll see what I mean when I finally post our notes on the mlpforums site and my DeviantArt page. I’ve already completed up till season 5, and and made rough outlines covering seasons 6-8. Season 9 doesn’t need much re-arranging, so I’ve kept it for the last. Hopefully, if everything goes as planned, our work will be complete by the end of this year, or the first week of January, 2021. And naturally, your work will be credited!

Thank you again for taking the time off to reply to my comment! If you have any more updates on your model, I’d love to check them out.

Have a great day!

- Dreamstar Moonlight

[Dreamstar Moonlight 44]

Hey @Quantum Pony!

I thought I’d share with you my theories about how long a ‘moon’ is in the equestrian calendar, since these may help you come up with an answer based on your model. So, without further ado, let me present the possible answers to the most headscratching, annoyingly tiresome question:

"How long is a moon?"

This topic has been speculated for so long that now there are now several varying answers to this question. The commonest answers are:

1) 1 moon = 1 lunar cycle; approximately 27-29 days (but less than a month)

2) 1 moon = 3.42 days (average length of each phase of the moon)

3) 1 moon = approximately a week

4) "Many moons" is an arbitrary term to mean a very long period of time. Kinda like how we say "it's been ages since we last met".

Theory (1): 1 moon = 1 lunar cycle: 27-29 days

This theory is most widely accepted, and it does explain why Twilight freaked out when Luna told her the portal to the Equestria Girls world would close in 3 days, and Twilight won't be able to return to Equestria for another 30 moons (approximately 3 years). It also makes sense for Twilight and her friends to meet "once a moon" (once every 27-29 days) when she establishes the Council of Friendship.

But this concept throws a hammer in the works if you consider Granny Smith was speaking facts when she mentioned that the Apple Family Reunion takes place every 100 moons. That means the Apples hold a reunion every 8 years or so. But seeing that there was a reunion in the pilot episode and another in season 3, and the fact that seasons 1-3 take place within a single year, it makes much more sense if 1 moon = 3.42 days so that 100 moons = 342 days, thus placing Apple Family Reunion 23 days before Summer Sun Celebration (June 21) in season 4.

Also, if according to your hypothesis, the moon goes through all of its phases during a single day, then this theory goes down the drain. Also, if you assume that 1 moon equals 1 day, well, that theory wouldn’t hold water one bit. I doubt the Apples will hold reunions every 3 months if we go by the logic. And the Council of Friendship would have to meet every single day. We know that's not the case.

Theory (2): 1 moon = approximately 3 – 3.42 days

Going by this theory, when 100 moons have passed, that means it's been 342 days since the first reunion we saw in the pilot episode when Twilight first came to Ponyville. Assuming that an Equestrian year has 365 days, the Apple Family Reunion we saw in season 3 takes place around 28^th of May  (23 days before the Summer Sun Celebration on June 21).

When Twilight suggested that she and her friends meet once a moon' (The Last Problem), and Rainbow's comment to Luster Dawn that they meet "this time, every moon) .....Do you think it's plausible that they meet every 4 days (the closest approximation to 3.42)? Or does it seem to be too short a period?  Granted, meeting once a month makes sense considering they all have jobs and are trying to schedule a meeting with the ruler of the land, but....

 

Also, another user gave a plausible explanation to this theory; their reason being (and I quote):

 

“.......Assuming the portal works once every 90 days (~1 season on Earth): There would be an astronomical reason for the portal to be opened on each of the equinoxes and solstices: the combination of the inclination of the planet, the elliptical shape of its orbit and its rotation will provide the exact same predetermined alignment with a distant star (if it was programmed to recognized it through typical parameters like "ascension" and "declination"; then establish a connection). This is a "brute force" safe mechanism. If the system had an ansible to look for [like the book] as a reference to draw 3 spatial coordinates (using 3 known points visible from both planets used as "zero" for reference) and the point of origin [the statue itself]; then it will work just like a Stargate. The occultation of that star by the local moon of the planet interrupts the connection [probably a safety mechanism prevents its use since the matter/energy transmission could be affected by its local gravity well ]; then when Pony! Twilight overrides this, she risks having a "telefrag" if she uses it at the night when the moon is high [both in Rainbow Rocks and The Friendship Games, the portal was used (or tried to be accesed) always during the day; maybe because she has figured this problem].”

Theory 3) 1 moon = approximately a week

Honestly, I haven’t found anything to support this theory. So I’ll just leave it like that for the time being.

Anyway, hope you find this useful!

As always, I’d love to hear which theory you support based on your model of the solar system!

Have a fantastic day!

-          Dreamstar Moonlight