10
$\begingroup$

I am making a game with the explorable world divided into multiple labeled regions. There is great convenience and simplicity in being able to reference the cardinal directions when labeling these regions and subregions within them (e.g Chozo Ruins East). However, the explorable world of my game just so happens to take place on a tidally-locked eyeball planet, with the distinct regions consisting of left along the band, right along the band, the hot area towards the sun, and the freezing area away from the sun. As such a planet doesn't have a north pole, there isn't really a basis for the cardinal directions as we use them.

Is there an acceptable way to regain this naming convenience, perhaps with an equivalent of the cardinal directions or an alternate way of defining them that makes sense? In the sense of say, if future humans were to colonize this planet, how might they casually refer to directions?

Improve this question
$\endgroup$
12
  • 1
    $\begingroup$ @sphennings Because eventually humans will step foot on such planets, and they will need or come up with simple directions to reference for convenience. Unless a basis for such directions already exists in real life (if they do it has eclipsed my knowledge and research), which is why I am asking here. This is not a brainstorming question, or rather, there are related questions on the sidebar that seem even more brainstormy than this one but have recieved a specific "best" answer based on their provided parameters. $\endgroup$
    – ZarHakkar
    Commented Jan 7 at 2:43
  • 1
    $\begingroup$ @sphennings Not necessarily. Not all coordinate/direction systems are equally valid in the context of the question, that being of which is most intuitive and easily presented to a modern gaming audience. Polar coordinates would be a lot less easily palatable than say, alternative but sensical names for NESW. It goes to some assumption that concepts that are intuitive to modern humans would also probably be at least still somewhat intuitive to future humans. $\endgroup$
    – ZarHakkar
    Commented Jan 7 at 3:48
  • 1
    $\begingroup$ @sphennings I agree that there is overlap between the various bounds of this question. However, of the possible SE sites to ask it on, I determined that Worldbuilding was the most pertinent one. Yes, the question asks to take into account one Doylist factor which might be related to game design (which it doesn't have to be, this could easily be for a movie or novel), but this is certainly not a question about game design. Additionally, Worldbuilding is no stranger to Doylist factors in world design as well. $\endgroup$
    – ZarHakkar
    Commented Jan 7 at 5:52
  • 4
    $\begingroup$ I disagree that there are multiple possible correct answers to this. The "warmward/coldward" differentiation has been applied in every civilization that has traveled far enough to know that there's a difference. I suggest that someone would have to show me a case where that wasn't used in real life for me to believe that it wouldn't apply in a fictional world. The only difference would be that they'd have to use other planets or stars for reference to where they were clockwise or counterclockwise. $\endgroup$
    – Robert Rapplean
    Commented Jan 7 at 9:22
  • 1
    $\begingroup$ Is there a moon or moons? $\endgroup$
    – Escaped dental patient.
    Commented Jan 8 at 2:59

6 Answers 6

Reset to default
14
$\begingroup$

Humans who colonize your planet might use North and South as we use them, as a couple other answers have stated. Natives wouldn't.

The dominant, most well-defined direction is towards the planet's Sun, and if the natives have a concept of "pole", it would be the line between the planet and the Sun, not the planet's axis of rotation. If you want to use "South" and "North" as main directions, one of those should be towards the Sun, and the other away from it. Or you could drop those direction names entirely, and use something like "Sunward", with maybe "Coldward" or "Darkward" for the opposite direction. Maps would have Sunward on top. The other two directions could use East and West, or you could make up names for those as well.

I think human colonizers, even if they started out with the astronomical definitions based on the planet's rotation, would quickly pivot to orient the same way. You could even mention in game how the original directions were different, but changed quickly because "no one liked it". That could avoid a lot of email complaints...

Improve this answer
$\endgroup$
2
  • 5
    $\begingroup$ This came to mind for me too. For a tidally locked planet, for any given location the sun will be at a fixed point in the sky. Sunward is then the logical direction when you move with the sun in your face, though 'Coldward' and 'Darkward' would only make sense once the natives progress past moving short distances. Something like 'Shadeward'? As your shadow is then always in front of you. The perpendicular directions are interesting; perhaps something as simple as 'Sunleft' and 'Sunright' as alternatives for East and West. $\endgroup$
    – pbeentje
    Commented Jan 9 at 9:36
  • $\begingroup$ I like this answer and the comment in terms of perspective. Yes, native inhabitants will be able to calculate the N/S poles of rotation, and the E/W poles tangential to orbital path, and they'll be able to do so at a surprisingly early tech level. Those facts will be of interest to specialists and trivia nerds, and probably a partial basis for a lat/long-equivalent coordinate system. They will not be how anyone gives directions. Sunward and sunleft/sunright (or cold/dark-oriented terms, if that's more culturally salient) is simple and intuitive. No one needs a compass when shadows never shift. $\endgroup$
    – Jay McEh
    Commented Jan 9 at 16:38
31
$\begingroup$

There is a natural coordinate system

The north and south poles have their normal definitions. Tidally locked means that the period of rotation is equal to the period of revolution, nothing more. The planet still has an axis of rotation, and it has a north pole and a south pole. The difference from a not-tidally locked planet is that the tidal lock provides for a natural prime meridian. For example, see the coordinate system used for our tidally locked Moon.

  • North pole: The pole around which the planet rotates counterclockwise.

  • South pole: The pole around which the planet rotates clockwise.

  • Prime meridian: The meridian which divides the star-facing hemisphere into two equal halves. Or they can choose as prime meridian the meridian which runs along the teminator. (Hat tip to @Chieron.) These are the only two natural choices.

Improve this answer
$\endgroup$
11
  • 6
    $\begingroup$ To add: the north and south poles could be determined by observing the stars, as the celestial sphere would appear to rotate around the axis during the year. And the best prime meridian is just the meridian that is aligned with the terminator line - everything remotely habitable in along this line (all other regions are too hot or cold to really matter). $\endgroup$
    – Chieron
    Commented Jan 7 at 21:27
  • 1
    $\begingroup$ @Chieron: Added as a second natural option. $\endgroup$
    – AlexP
    Commented Jan 8 at 12:34
  • 1
    $\begingroup$ @AlexP There are two choices of meridians that run along the terminator, and two that equally divide the the star-facing hemisphere (although I don't suppose you'd put the prime meridian facing away from the star) - there are three/four natural options. $\endgroup$
    – Nuclear Hoagie
    Commented Jan 8 at 14:04
  • 1
    $\begingroup$ The natural coordinate system may exist, but it probably wasn't known about for hundreds of years of map-making. If there is a narrow band of habitability, it is probably in an area with eternal sunlight. Any area where stars are visible to the naked eye is probably too cold and barren to remain habitable. Even if explorers ventured into it, who would believe their stories that there were things called 'stars' that moved slowly across the sky? $\endgroup$
    – Jason Goemaat
    Commented Jan 8 at 19:40
  • 1
    $\begingroup$ @AlexP So an arbitrary convention. $\endgroup$
    – nasch
    Commented Jan 10 at 23:52
24
$\begingroup$

There are fixed poles on your planet: noon and midnight.

Where the sun is directly overhead, that's the noon pole. The exactly opposite location is the midnight pole. The equator is the dividing line between day and night. Coordinates can be plotted from there.

One notes that the 0 degree of longitude will be arbitrary -- as it is on Earth. It took some time to standardize on Greenwich. A prominent location such as an observatory, or perhaps the landing site, would be as good as a way to pick it as any.

Improve this answer
$\endgroup$
10
  • 6
    $\begingroup$ +1. But the 0 degree of latitude need not necessarily be 100% arbitrary...the leading point on the planet in its orbit, or the trailing point, strike me as fairly elegant choices. $\endgroup$
    – Qami
    Commented Jan 7 at 4:07
  • 2
    $\begingroup$ You actually would have a reference for zero degrees longitude. The planet doesn't turn, but it still orbits the star, so the 0 lat could be the north or south pole of the planet's orbital axis. Or it might be the capital city of the most important empire. That works, too. $\endgroup$
    – Robert Rapplean
    Commented Jan 7 at 9:24
  • 4
    $\begingroup$ We actually have four poles: hot/noon and cold/midnight, north and south (determined by the rotation in relation to the celestial sphere). Taking one prime direction to be the terminator meridian (habitable zone/temperature equator) and the other either the rotational equator or the meridian crossing all 4 poles should be fine (and non-arbitrary). $\endgroup$
    – Chieron
    Commented Jan 7 at 21:30
  • 1
    $\begingroup$ @Chieron There's a reason why observing the stars was a profession in ancient times. Also, both our poles were completely inhospitable when their existence was determined. Indeed those who determined them thought you could not go past the equator. $\endgroup$
    – Mary
    Commented Jan 8 at 13:19
  • 5
    $\begingroup$ @Chieron It's actually six poles - four additional poles can be defined on synchronously rotating bodies in addition the two poles of rotation. The ones on the inside/outside of the orbit are called the near and far poles (noon and midnight), and the points furthest forward/back on the orbital path are called the leading and trailing poles. $\endgroup$
    – Nuclear Hoagie
    Commented Jan 8 at 17:23
10
$\begingroup$

The planet will have poles because it will rotate. A planet tidally locked to its star will have a rotation period equal to its orbital period around the star. So the star that the planet orbits will not appear to rise in one direction and set in the opposite direction.

But if anyone lives in regions where the sky is dark enough to see the stars they will notice the the stars slowly changing over the the course of the planet's rotation and orbital period. An entire hemisphere of the sky will slowly be replaced by the other hemisphere in half an orbital period and then slowly turn to the first hemisphere in the second half of the orbital period. So where the stars can be seen east will be the direction where the stars rise and west will be the opposite direction where the stars set.

The orbital period of a habitable tidally locked planet should be from a few Earth weeks to a few Earth months long, unless a writer doesn't care about scientific accuracy.

The rotation of the planet will have effects on its structure. The Earth is an oblate spheroid shape because of its rotation. The rotation of a tidally locked world will be much slower and the planet will be much closer to a true sphere than Earth is. But a satellite put in a polar orbit and using radar or laser range finding to measure the distance to the surface will measure hills and valleys, and also measure that sea level will be farther below the orbit near the poles than near the equator.

On Earth space vehicles launched into orbit are usually launched in an eastward direction to take advantage of their momentum from Earth's spin. On a tidally locked planet rotation will be much slower and that effect will be much slighter, but possibly it will still be the practice to launch toward the east.

The natives of the planet will be as advanced as the story requires. They might not be able to live where the sky is dark enough to see the stars; if so they won't notice that the heavens revolve around their planet - or that their planet rotates beneath the heavens.

They might not be able to measure the slightly oblate shape of their planet.

Or they might be advanced enough to know that their planet slowly rotates and has directions which we would call north and south, east and west.

And if any Earth human characters visit the planet in the story, they should be advanced enough to now the planet slowly rotates and to know it has north and south, east and west directions, in addition to any native set of directions.

Improve this answer
$\endgroup$
1
$\begingroup$

To keep things easy, I'd use standard NSEW coordinates rather than inventing new words, unless you specifically want to flag that things are different here. If it's just background info that you don't expect people to really interact with, just use north/south/east/west. You can pretend they're translations of native words or whatever. But most people are already familiar with NSEW so it's probably not worth it to introduce new names.

You could define them in a few different ways, depending on how you want people to think about these.

  • If temperature and climate are important, then use north = cold/away from the sun and south = hot/towards the sun. If y'all are in the southern hemisphere and you think south is cold, flip it.
  • If local navigation within a climate region is more important, then go with east = towards the sun.

Your sky will have a celestial north and south pole, too, where an astronomer on the dark side of the planet will see all the other stars rotate around the poles through the course of a year. You could put the equivalent of the Prime Meridian directly underneath one of those poles, if you care enough to. But I expect it would take the astronomers a while to discover that, since the stars would have only one rotation per year and a year isn't very meaningful on an eyeball planet. And people were fine navigating without a Prime Meridian for a very long time.

Improve this answer
$\endgroup$
-1
$\begingroup$

You could create a system of directions based on landmarks rather than natural geology. This would also allow you to have a system with more than 4 directions in it. For example, you could have an eight way system, with the four largest being NESW and a four trading cities being NE, SE, SW, and NW.

You could have different systems for each region if you wanted.

Improve this answer
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .