# Could this work...... using stars to tell the months??????



## WeilderOfTheMonkeyBlade (Dec 8, 2013)

Could this be plausible, I don't know much about stars and how they move about, why some sometimes shine brighter and whatnot, but I had an idea that there are 12 stars (one for each month, isn't that convenient :0) And each "month" a different star shines bright, in a cycle, so you can effectively tell what month it is by which star shines (brightly) in the sky. 

and by Brightly, I mean you wont be able to get mixed up between these stars and normal stars. It is like getting mixed up between a torch and car headlights. Any way, that's the idea, know I just need some clever people to tell me if it could work. 

I'm not a fan off having to use magic to make this works, but I suppose I could If I wanted to, but that's why I'm posting this, to see if it could be done with mundane things like physics.


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## buyjupiter (Dec 8, 2013)

Variable stars! No magic necessary. I'm going to go a bit geeky on you, here, but I'll try to keep it from going into equations. 

A variable star does exactly what you want it to do. There are two types: intrinsic--the brightness fluctuates as a function of the output of energy for that star, or extrinsic--an object passes before the star, dimming the brightness for some period of time.

Intrinsic variable stars would probably work best, and you'd have a couple of options to get the job done.

For example:

-Long-period variable stars: can vary in brightness anywhere from 80 days to 1000+ days, and can sometimes be irregular.

-dwarf novae (if you want to go explosive): a binary star system where one of the stars is larger and one is a dwarf star, the dwarf star "steals" matter from the larger star and this process usually lasts 5-20 days or so, with gaps of a few hundred days between flares

Extrinsic variable stars tend to be the result of a binary system where one star passes in front of the other, obstructing the star from view. This tends to be something that lasts a few minutes at most, and potentially hours in very rare cases. You could always modify it to work for your needs, but since there are other better suited types above, I might use those instead.

Examples of variable stars:

Betelgeuse (in Orion)
Proxima Centauri (Centaurus)
Most of the stars in Cepheus (which is where the Cephid variable star gets its name)
Algol (Perseus)
Polaris (Ursa Minor)

If your society is pre-Industrialized, you're going to need a section of sky that is full of fairly dim stars for there to be a noticeable difference. Even in the countryside with no binoculars/telescope, it's hard to tell when Polaris dims versus brightens. There are a ton of stars in the sky in that general region. 

You'll also need to increase the magnitude of the variable star by, goodness, 50-75%. Most of the famous variable stars aren't that bright. For reference, Sirius (Dog Star) is the brightest star in the sky at -1.46 magnitude. Betelgeuse (9th brightest star) is anywhere from 0.2 to 1.2. (The point being that the further along the negative side of the scale the brighter the star is, the sun is -27; and the further along the positive side the dimmer.)

I hope this helps! /astronomy geekery


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## skip.knox (Dec 8, 2013)

Variable stars are a nice touch. It'd be pretty extraordinary to have 12 stars all moving on 30 day cycles, but hey, this is fantasy.

The obvious thing to choose would be not varying brightness but constellations. As in the Zodiac. But maybe that puts your fantasy world too close to Real World.

You might think to use 12 planets, but there's no way in physics to get them to the same place at the same time of year. Different orbits and all.

How about moons? Not twelve, but one with a year-long phase, or a couple of moons or even three that could in differing configurations mark the different months.


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## ThinkerX (Dec 8, 2013)

Might want to consider a combo of variability and brightness (or lack thereof).

1st month: dominant star 'winks' in brightness on a 24 hour cycle, give or take

2nd month: tight triangle of three bright stars of steady luminosity

3rd month: dominant star is a long term variable

4th month: NO bright stars, aka the 'dark month'  (with attendent superstitions about evil gods swallowing the light)

5th month: 'shooting stars' - large group of meteors making a close pass of the planet during this time each year (with attendent superstitions about falling spirits)

ect


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## Saigonnus (Dec 8, 2013)

It could, it is fact that as the planet orbits the sun, certain stars/ other planets in the solar system come into view only during certain times of year from their closeness to the planet. For example, August on earth is usually when Mars is the closest to us, and appears as a red dot in the heavens. All other times of year, it is invisible to the naked eye. 

I think combining other planets in the solar system as well as constellations (also consistent in the heavens and visible during only part of the year) could be a good basis for a calender. I would say the shooting star effect could happen when a planet passes in close enough proximity to an asteroid belt that the gravitational forces of the planet pulls at the smaller objects in the field. 

I think the shooting stars is a bit risky in a geologic sense, if a large enough object happens to be in range when the planet passes by, it could drop a city-sized chunk of rock onto the planet, extinguishing life. On the other hand, it might be chunks of ice instead of rock and at the furthest point from the sun that the planet gets.. (winter)


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## ThinkerX (Dec 8, 2013)

> I think the shooting stars is a bit risky in a geologic sense, if a large enough object happens to be in range when the planet passes by, it could drop a city-sized chunk of rock onto the planet, extinguishing life. On the other hand, it might be chunks of ice instead of rock and at the furthest point from the sun that the planet gets.. (winter)



Earth gets hit by at least one such frequent meteor shower (Leonids, if memory serves).  Might also make for some interesting mythology based around a larger than normal rock making it through the atmosphere - something like the event in Russia a year or so back.  Might also make for an interesting tale.  'The dark god unleashed his wrath from the heavens.'

I do like the 'Mars' idea.  I'd suggest having the planet large enough to appear as an actual disk to the unaided eye, instead of a point of light.  I've something similiar in my own cosmos.


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## Saigonnus (Dec 8, 2013)

ThinkerX said:


> I do like the 'Mars' idea.  I'd suggest having the planet large enough to appear as an actual disk to the unaided eye, instead of a point of light.  I've something similiar in my own cosmos.



Yeah, the rest of the time of the year could be far enough that it's just another point of light in the night sky.


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## buyjupiter (Dec 8, 2013)

I should also point out that anything you do astronomically, you'll always have to take into account where your moon will be (if you have one--and if you don't I can point out a few things you might consider below).

So, if you go with a variable star approach, it needs to be pretty distant from the moon for it to be visible. There would be exceptions to this (new moon, later moon rise, earlier moon rise), but for the most part the moon would be brighter than anything surrounding it for quite a ways.

Constellations would fare better nearer to the moon's path, because there would be more stars, but they'd still need to be pretty bright/not too near to the moon.

Planets, well it'd depend on how close they are to the "Earth", and if they're not that close, how close they are to the moon.

Moon stuff:

Most moons are reflective due to composition (rock) and lack of obscuring atmosphere. 

If you have no moon in your night sky, you're not going to have a very strong tide (if at all) and the fishermen and sailors in your world would have to compensate for that effect.

Likewise, if you have more than one moon, you'll see an increase in tidal effects. My understanding of tidal forces in a multi-object system is limited, but some of the gravitational effects would "cancel" out. When a moon dips closer to the planet's surface the increase in tidal force would be noticeable. I think in a multi-moon system (like Jupiter or Saturn), the orbital mechanics pretty much require the moons to dip in and out of a close orbit. I believe most of them are in a decaying orbit (which means that in an eon or so the moon will crash into the planet's surface).

The increase in tidal forces would have an impact on your coastal regions. I imagine that any society that has to frequently pack up and move because of higher tides might take longer to develop.


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## psychotick (Dec 10, 2013)

Hi,

I don't buy twelve different stars deciding to shine brighter once a month on different months. Maybe I'm too much of a science nerd but it sounds contrived to me. However I don't see why you can't have just one star going through a monthly cycle of shining brighter and dimmer. It involves less coincidence. But why do you need stars to do this when you have a moon? Or is there no moon in your world?

If you need the moon to tell you which particular month it is you can do this quite easily. Simply have the moon have it's own axial spin so that it spins slowly over the course of a year. If it has some striking geographic features, say mountain ranges that look like lines that perhaps resemble a face, then every full moon you would be able to look up and see whether the face is staring at you, soon to stare at you, or has finished staring and moved on to stare at something else.

Cheers, Greg.


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## WeilderOfTheMonkeyBlade (Dec 10, 2013)

OK people, I shall give you a bit of my own science.... MIND= BLOWN, to the power of ALOT!!!!  
But thank you, you have given me a lot of food for thought- it turns out what seems to be a simple (ish) idea basically isn't!!!! But, I really appreciate all this info  Some of you mentioned using the phases of the moons, but I don't really want to do that, it has been done quite a lot before, and I wanted to come up with a new, daring, and extremely complicated new way....


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## UnknownCause (Dec 10, 2013)

I think it's a good idea. Be careful though, the Egyptians and the Mayans might call you to order a lawsuit.


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## buyjupiter (Dec 10, 2013)

psychotick said:


> Hi,
> 
> I don't buy twelve different stars deciding to shine brighter once a month on different months. Maybe I'm too much of a science nerd but it sounds contrived to me. However I don't see why you can't have just one star going through a monthly cycle of shining brighter and dimmer. It involves less coincidence. But why do you need stars to do this when you have a moon? Or is there no moon in your world?



Given that there are at least 100,000 variable stars (with some estimates putting it closer to ~300k, exo-galactic ones as well), it wouldn't be too much of a stretch. 12 stars being long period variables wouldn't be unlikely. However, the unlikeliness (or stretch) would be the magnitude (brightness) and the proximity to the planet in question.

I should have been an astrophysicist, but PhD's cost way too much.


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## psychotick (Dec 14, 2013)

Hi,

Actually a hundred thousand stars wouldn't be anywhere enough in my view to give you these odds, because each star has to shine for a particular month and then not for eleven more. Variable stars don't generally do that, but you want twelve to follow this unlikely cycle in perfect order. As for seeing them with your naked eye and working out that one is brighter than it was last month, that's also going to be tricky and most people probably wouldn't notice it.

The moon is easy to see. It can and does have the right periodicity. And it would be no trouble to have mountain ranges on it if they were large enough, to look like the lines of a face. An as an added bonus you could see this leading to endless religions - a god you can actually see!

Cheers, Greg.


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## buyjupiter (Dec 15, 2013)

psychotick said:


> Hi,
> 
> Actually a hundred thousand stars wouldn't be anywhere enough in my view to give you these odds, because each star has to shine for a particular month and then not for eleven more. Variable stars don't generally do that, but you want twelve to follow this unlikely cycle in perfect order. As for seeing them with your naked eye and working out that one is brighter than it was last month, that's also going to be tricky and most people probably wouldn't notice it.
> 
> ...



Can I ask how you're drawing the conclusion that 100,000 variable stars (not just regular stars which are much more numerous), wouldn't lend itself to allowing 12 stars be long-period variables brighter for one month out of the year, and dimmer for the other 11? (I'd be more than happy to continue discussing this via PM if you like. I don't want to bore anyone with going full on geek with the various types, subtypes, and definitions of periodicity and luminosity for those subtypes.)

Our moon is a rare case, and extrapolating what we experience as the "norm" isn't accurate. A moon could have the "right" periodicity (a thirty day cycle) or it could have a five hour revolution around the planet or it could have a three month periodicity. Depends on how many moons, how close the moons are to the planet and orbital mechanics. Anything moon-based would require phases, and counting, which wouldn't be what the OP was asking for. 

But anywho, if anyone wants more in depth detail on how to make a variable star calendar work, I'd be happy to help out as best I can.


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## Benjamin Clayborne (Dec 15, 2013)

My first question would be: Why do you want to do this? If it's just to add some random magicalness to the world you're creating, that's fine, I suppose... but astronomically it's a really strange approach. If there's going to be 12 variable stars that each stay bright for exactly 1 month and cycle in order (and no other bright variable stars during that period to cause confusion), that's something that pretty much has to have been arranged by some intelligence. The odds against it occurring naturally are... *sunglasses* astronomical.

Telling the month by the stars is pretty easy here in the real world, so I don't know why it would need to be different in your world. Even if the characters in your world have no concept of astronomy (although keep in mind that even the ancients in our world had already figured out much of it, except for heliocentrism before the Copernican era), you still need to decide the ground rules for reality in your universe. An axially-tilted world orbiting a star in a galaxy is going to have seasons, and will also see different constellations as the year progresses. It's not hard to learn those constellations and figure out what month it is by simply seeing what constellation is rising when the sun sets.


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## buyjupiter (Dec 15, 2013)

Benjamin Clayborne said:


> My first question would be: Why do you want to do this? If it's just to add some random magicalness to the world you're creating, that's fine, I suppose... but astronomically it's a really strange approach. If there's going to be 12 variable stars that each stay bright for exactly 1 month and cycle in order (and no other bright variable stars during that period to cause confusion), that's something that pretty much has to have been arranged by some intelligence. The odds against it occurring naturally are... *sunglasses* astronomical.
> 
> Telling the month by the stars is pretty easy here in the real world, so I don't know why it would need to be different in your world. Even if the characters in your world have no concept of astronomy (although keep in mind that even the ancients in our world had already figured out much of it, except for heliocentrism before the Copernican era), you still need to decide the ground rules for reality in your universe. An axially-tilted world orbiting a star in a galaxy is going to have seasons, and will also see different constellations as the year progresses. It's not hard to learn those constellations and figure out what month it is by simply seeing what constellation is rising when the sun sets.



The OP has already addressed the reasoning behind making up a new calendar system. I'm not the OP. I only wanted to answer their question, and give enough scientifically sound methods of accomplishing that task.

I'd thought this was the place to discuss how to make _fantastical _ideas work. Apparently, I joined the wrong forum.


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## buyjupiter (Dec 15, 2013)

buyjupiter said:


> The OP has already addressed the reasoning behind making up a new calendar system. I'm not the OP. I only wanted to answer their question, and give enough scientifically sound methods of accomplishing that task.
> 
> I'd thought this was the place to discuss how to make _fantastical _ideas work. Apparently, I joined the wrong forum.



I'm sorry for the snarkiness, Benjamin. It wasn't directed at you, or at anyone else. I'm just a bit frustrated that after the research, and the care I've taken to make sure that I'm up to date with my science, I've felt like I've been dismissed out of hand. This is a long standing frustration that I've had numerous times in dealing with being a girl who knows science, and actually knows what the heck she's talking about (sometimes). It was unfair of me to take it out on any of you.

I've tried to just geek out, but I fear I may have crossed the line into talking _at _some of y'all instead of _with _you. I've tried not to come across as a know-it-all, and that I am the only one who knows anything about the subject and I'm right and you're wrong, etc...but I think I failed in that a couple of posts back. 

I'd like to sincerely apologize for ruffling anyone's feathers, and in future, I'll try to keep out of astronomical discussions, as that seems to be something I'm a bit *too* passionate about. *adding astronomy to list of things to keep out of polite conversation*


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## Benjamin Clayborne (Dec 15, 2013)

buyjupiter said:


> I'm sorry for the snarkiness, Benjamin. It wasn't directed at you, or at anyone else. I'm just a bit frustrated that after the research, and the care I've taken to make sure that I'm up to date with my science, I've felt like I've been dismissed out of hand. This is a long standing frustration that I've had numerous times in dealing with being a girl who knows science, and actually knows what the heck she's talking about (sometimes). It was unfair of me to take it out on any of you.
> 
> I've tried to just geek out, but I fear I may have crossed the line into talking _at _some of y'all instead of _with _you. I've tried not to come across as a know-it-all, and that I am the only one who knows anything about the subject and I'm right and you're wrong, etc...but I think I failed in that a couple of posts back.
> 
> I'd like to sincerely apologize for ruffling anyone's feathers, and in future, I'll try to keep out of astronomical discussions, as that seems to be something I'm a bit *too* passionate about. *adding astronomy to list of things to keep out of polite conversation*



No offense taken. I have a thicker skin than that. 

There's nothing wrong with fantastical ideas, but if someone comes up with a fantastical idea just for its own sake, and tries to cram it into a story that has nothing to do with it, they're probably hurting the story. If the OP wants to have 12 variable stars that indicate the month, that's fine, but whether it works _in the story_ is going to depend on the tone of the story. If it's an ethereal, wistful piece where rationality is secondary to emotion, then something fantastical (but nonsensical) can be perfectly in place. If it's an otherwise "realistic" story (that is, people in the story behave similarly to people in real life, and things in the story that happen make logical sense within that framework, and it's more about a progression of events and character development than about tone and feeling), then it might just come off as weird to the reader.

In other words, the *reader* might perceive that it's some weird idea that the author crammed in there, rather than as an integral part of the world. When the readers can see the seams, that's bad.

In this case, I don't see where the OP explained the need for this mechanism, other than wanting to come up with something complex and different, which is why I asked what the intent was.


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## SM-Dreamer (Dec 17, 2013)

I don't remember where I read this, but I read about one ancient culture that counted its 'weeks' by the constellations that rose on the horizon. Roughly 10 days if I'm remembering correctly. Which I might not be; it's a vague notion from a cursory look at different calendrical systems. Still, could be interesting to use?


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## wordwalker (Dec 20, 2013)

Benjamin Clayborne said:


> No offense taken. I have a thicker skin than that.
> 
> There's nothing wrong with fantastical ideas, but if someone comes up with a fantastical idea just for its own sake, and tries to cram it into a story that has nothing to do with it, they're probably hurting the story. If the OP wants to have 12 variable stars that indicate the month, that's fine, but whether it works _in the story_ is going to depend on the tone of the story. If it's an ethereal, wistful piece where rationality is secondary to emotion, then something fantastical (but nonsensical) can be perfectly in place. If it's an otherwise "realistic" story (that is, people in the story behave similarly to people in real life, and things in the story that happen make logical sense within that framework, and it's more about a progression of events and character development than about tone and feeling), then it might just come off as weird to the reader.
> 
> ...



Just wanted to say, this does spell things out well, Benjamin. We writers should know if the piece we add is needs to be smoothed in as part of the whole world because it makes less sense on its own, or if it's also bringing some close-to-ours science with it for support... and anything that isn't solid enough on the first grounds needs plenty of the first. Because too often it does happen like you say, a writer jams an idea in without seeing the need to make it fit (maybe thinking it follows science better than it does), and "seeing the seams" is exactly why that hurts the story, no matter how cool the thing might be.

A viewpoint for us all to keep in mind.


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