How to describe someones age when they live on another planet?

[X Equestris]

If I'm not mistaken, the planet and star should still move across the moon's sky, even if it's tidally locked. If nothing else, the constellations would probably shift as the moon followed its planet around the star. That could function as the equivalent of a year.

Edit: the planet would likely have phases as well. Could be an interesting angle to work.

 

[psychotick]

Hi,

If the moon is tidally locked around the planet with complete synchronicity then I suspect you would actually have any society living there with little appreciation of time to begin with. There would be only one appreciable light source for the people on the planet side of the moon - ie the planet, because it's going to be the largest thing in the sky by miles. For tidal locking to occur you would normally have one very small moon in close proximity to a much larger planet. So the planet's simply going to dominate unless it reflects little light. Even if the sun's an appreciable object because of its brightness, you would have (working off our moon's cycle) the equivalent of two weeks with it visible and two weeks without it. That means that not only days don't exist (or are alternatively four Earth weeks long) but neither do seasons, and even years become only academic things depending on how close the planet is to the sun.

With that in mind I think you would end up with a society that has little appreciation of time. And what appreciation they do have would be largely based on non-astronomical phenomena. So for example the age of schooling - when they are ready to start learning reading, writing complex physics. The age of menstruation / development of secondary sexual characteristics. The age when you achieve full height. So maybe you define time very differently. You don't have days, weeks, months, seasons or years. You have the age at which certain things normally happen, such as mastering certain concepts, being able to run a certain distance, passing particular tests. Things become much more relative - pun intended!

But you can have a lot of fun with this concept. For example, do short people literally never reach adulthood?! Do intellectually slow people never do the same?! So you could have say a seventy (Earth) year old man literally regarded as a child because he's short or couldn't master Latin(?)!

Cheers, Greg.

 

[Nomadica]

@ X Equestris The sun will move across the sky but the planet won't. It will however have land marks that will rotate in and out of view that could be used as to measure time as pmmg pointed out. It will have a year because it does make a full orbit around the sun but the time frame it takes to make that trip will likely be different than earths.

@psychotick When I referred to seasons earlier I meant that the long warm light and cool dark cycle will be viewed more like seasons. Though I do believe that the moon could have true seasons if it's orbit around the planet was tilted in relation to the planets orbit around the sun. But my moon Isn't so it doesn't have true seasons. The sun will be visible like on earth but you are right they wont appreciate time like we do.

 

[psychotick]

Hi,

I'm not sure even that tilted orbit around the planet would give your moon seasons. What you would see fromthe moon's planet facing side would be the planet rising higher and lower in the sky as the month long day (day?) progresses. But I don't think that works so well for the sun.

Cheers, Greg.

 

[Nomadica]

No, to create seasons, the orbit wouldn't be tilted in relation to the planet itself, just the planets orbit. The face of the moon would remain perfectly aligned so the view of the planet from the moon would remain stationary.

 

[FifthView]

Seasons are perfectly feasible for such a moon. The greatest factor would be its axial tilt in relation to the planet's plane of orbit, I think. Saturn's moon Titan could serve as an example.

So time could be measured in seasonal changes, just like on Earth. Early humans developed the concept of a year by noticing patterns in seasonal changes and the position of the sun in the sky. I have difficulty visualizing precisely how the sun would appear on that fictional moon, but a tilt would create a moving pattern for it as the year progressed.

I'd say that simply using "years" would be okay for the story, although how your people come to that concept of years might be somewhat different than how it happened in our own history. I'd guess that their equivalent of "month" might be something based on the day/night cycles. Perhaps one day followed by one night constitute a "month" although they'd have a different word since, heh, that word descends from "moon." (But this isn't completely different. The month was a measurement of lunar phases–and those phases are basically the progress of day/night cycles on the moon as the sun moves across its surface!)

So...seasonal changes. If you don't want to use "year," maybe you can reference passing time by directly addressing the visible changes in the seasons. This is like ye olde "five summers ago" or "My mother died in my ninth summer." You could be creative and reference landmarks like, "I'd experienced nine Yuna melts before my mother died" –assuming that Yuna is a river that freezes solid every winter and melts every summer on that moon. Or maybe there's migratory wildlife; if merqa is the term used for the annual migration of animals similar to, oh, reindeer or buffalo, then you'd say, "During the ninth merqa of my life, my mother died." (Perhaps "merqa" is an annual mass-moving of the humans also, following the herd.)

 

[X Equestris]

@ X Equestris The sun will move across the sky but the planet won't. It will however have land marks that will rotate in and out of view that could be used as to measure time as pmmg pointed out. It will have a year because it does make a full orbit around the sun but the time frame it takes to make that trip will likely be different than earths.

I'm not completely certain the landmarks would work. You'd get phases of the planet, which would obscure part those landmarks part of the time. And unless the planet's day is very long, like Venus', the landmarks would come around quite fast.

If I'm reading your diagram below correctly, the moon's orbit is tilted relative to the planet's, right? Like our Moon? That would lead to the planet moving a little across the sky in at least some locations. How noticeable would depend on the degree of the tilt. And if the orbit is elliptical, the planet will appear to grow or shrink.

 

[Michael K. Eidson]

My story takes place on a tidally locked moon so they don't even have days and nights. Though they do have long light and dark periods called elume and ebonly. My MC is trying to say that her mother died when she was around the equivalent of 9ish (+/- a year) in earth years but I don't want to use earth as a reference if I don't have to. I'm keeping earths reference to the first page and even then using it as minimally as possible. So how do I describe 9 in other ways?

For your story, how long does it take for:

1. the earth to revolve around the sun
2. the earth to rotate once on its axis
3. the moon to revolve around the earth

Also, what is the tilt of the moon's orbit around the earth in comparison to the earth's orbit around the sun?

All these things must be known before you can calculate what portions of the moon will be illuminated, when they will be illuminated, and how brightly they will be illuminated, whether by direct sunlight or reflected light from the earth.

Once you know the above, you can draw a series of diagrams, one for every, say, 1-degree of revolution of the earth around the sun, starting with the sun, earth, and moon in a "zero" position (say, when the moon is between the earth and the sun). Do the math, which shouldn't be difficult if you know your geometry and arithmetic, figure out where the earth will be in relation to the sun and the moon in relation to the earth, for each of 360 different positions of the earth in its orbit around the sun. You can draw lines representing sunlight on each diagram, both direct and reflected. You should see patterns emerge, and can use this to determine your periods of light and darkness. Even doing this for 10-degree increments, to reduce the number of diagrams, could be enlightening.

If the number of revolutions of the moon that occurs during one revolution of the earth around the sun is not an integer, then you need to do another set of diagrams to see how the moon is illuminated during the second earth year. Same for earth years three, four, five, etc., until the moon comes back to the same location it was in originally when earth is at its "zero" position.

If you are good at computer simulations, this would make for a good simulation project.

If you are good at using a 3D modeling/animation program with ray tracing / light reflection, you could set up a visual simulation of this, and play it back to see what happens.

On a final note, if you state in your story any info that let's the readers know or surmise the above bits of info, they will be able to do the simulations, if they so desire, and if your descriptions of the periods of darkness and light conflict with simulation results, some of your readers might call you on it. So if you don't do the simulations, you also shouldn't give away all the details about the revolutions, rotations, and axis tilt. You still run the risk that whatever info you give, someone may prove that it's theoretically impossible for it to happen as you've described. So, if you're not absolutely sure of your details, then the fewer details you give, the better protected you are against science-minded readers.

 

[Nomadica]

I had planed for fewer details because even if it all added up, I'm not an astrophysics so I cant tell if the calculations I made would leave the moon uninhabitable. Like frequent volcanic eruptions and thin atmosphere because the moon is too close to the planet and orbits too fast. This is what I have so far:

moon, Iso, is approximately earth size orbiting the planet Oriath which is 6x its diameter
color planet-orange, dusky pink and dusky purple in the right lighting with streaks
one other smaller white moon in between them, Isen , they align once every orbit
orbit 10 times a year
1 orbit = a dawning
oriath rotates 36 times a dawning
light time= elume
dark time= ebonly
sun set/waning= descent
sun rise/ waxing= ascent
yung dark= ebonfall


full oriath=lucin
waxing & waning oryith= waxing& waning
new oriath=dark oryith

side of iso facing planet=face
opposite side=end, aluce lucinai or lucless

Most of the races are on the face to take advantage of the light reflecting from oriath during the ebonly.

I imagine having the planet that big it would need to be less dense than earth to keep the moon inhabitable. But having a bigger planet would look nice from tho moon.

I wasn't planning on having seasons. the above discussion on rather a tidally locked moon COULD have seasons was just for the pleasure of it

 

[Nomadica]

If anyone is curious, this is Iso

Most people live on the middle continent on the east side of its great mountain range and on the east continent to the west of it's far east mountain range. Land is smaller on the side of the moon acing the planet due to more water being drawn to that side from the planets pull

 

[pmmg]

Very Nice. I like it.

 

[Yzjdriel]

There's nothing wrong with just saying that she's 9. The reader will just assume that there's a period of time roughly analogous to a year that they use to measure time the same way we measure years. They could even call this period of time a "year" and it wouldn't necessarily be a reference to earth. After all, it's highly unlikely they're speaking English in the story anyhow - you're "translating" the story from their language to the readers', so using terms the reader is familiar with makes perfect sense.

 

[Deleted member 10411]

My story takes place on a tidally locked moon so they don't even have days and nights. Though they do have long light and dark periods called elume and ebonly. My MC is trying to say that her mother died when she was around the equivalent of 9ish (+/- a year) in earth years but I don't want to use earth as a reference if I don't have to. I'm keeping earths reference to the first page and even then using it as minimally as possible. So how do I describe 9 in other ways?

In my world its usually with how many summers or winter's they've lived through, is this planet in the same solar system? How about how may times their moon travelled around its host star?

 

[Dankolisic]

My story takes place on a tidally locked moon so they don't even have days and nights. Though they do have long light and dark periods called elume and ebonly. My MC is trying to say that her mother died when she was around the equivalent of 9ish (+/- a year) in earth years but I don't want to use earth as a reference if I don't have to. I'm keeping earths reference to the first page and even then using it as minimally as possible. So how do I describe 9 in other ways?

well, on my world(which is a different planet far away from earth) there are no years, but frosts.
If a planet/moon is tidally locked, then they must have a different time measure. If there are no days or nights, how do they keep track of time? maybe by growth? " my mother died when my hair reached my back" which would imply it takes 9 years to grow hair that long, or something else. Like a moon that orbits the planet? "my mother died when I was only 55 moons old."

 

[Deleted member 10411]

well, on my world(which is a different planet far away from earth) there are no years, but frosts.
If a planet/moon is tidally locked, then they must have a different time measure. If there are no days or nights, how do they keep track of time? maybe by growth? " my mother died when my hair reached my back" which would imply it takes 9 years to grow hair that long, or something else. Like a moon that orbits the planet? "my mother died when I was only 55 moons old."

What I'm saying is that the moon that your characters live must orbit some sort of star, it may be tidaly locked but the moon would still orbit something, you could use cycles, like "my mother died during my 30th cycle." Your world sounds like quite a cool concept. Maybe there is a comet or something that passes over, every so many earth years and the people on the moon count that as 1 cycle.

 

[pmmg]

A moon orbits a planet.

A planet orbits a star.

The moon could be tidally locked to the planet, and the planet could be tidally locked to the star, and there would still be day/night cycles on the moon. If the planet is tidally locked, the planet might have one side permanently day and another permanently night, but not the moon. The moon goes around the planet, giving its back and front to the star as it goes. The period of that can vary depending on a lot of factors (and even not match what math might tell us if the Author wishes).

The only way a moon could not have a day/night cycle is if the star was dark, or the moon orbits around the poles in a perfectly perpendicular way and was tidally locked or rotated itself in a perfectly perpendicular way. Or some other strange, but improbable, anomaly, like maybe another bigger planet was between them and the star, and they never got out from behind it.

I suppose the planet itself could give off light, but that would likely cause more periods of brightness, not dark.

There are many ways to measure time without the day night cycle. We could measure by the loss of the last baby tooth, or the start of menstruation, or the length of hair one grows. Just need to be creative about it. Astrologically, things in the sky would still change, and could be used to measure by.

The OP'er is not likely coming back for this, so....