View Full Version : Advise on Alien world and galaxy

11-12-2012, 10:18 AM
Greetings, it looks like you all have a nice community here. After reading some posts, it looks like I could get some insight on a my RPG maps. My RPG is very much a work in progress but the idea is a galaxy spanning RPG with magic being strong in the core but weaker towards the rim and technology being advanced in the rim but failing as it progresses towards the core. After doing some research I like the galactic cardinal directions of: Spinward, Trailing, Coreward and Rimward.
My problem is I would also like some alien sounding directions for planetary navigation and mapping other than North, South, East, and West. I also have aliens that live in red dwarf stars, black holes, and asteroids so I want something flexible. I know all these objects spin so that gives me spinward and trailing but since I'm dealing with sphere(ish) bodies I need more than just the terms I use for the mostly flat galaxy. I keeping getting hung up on differentiating the poles. I also want to avoid magnetic terms.
Any ideas for some new cardinal directions that would apply to any spinning body?

And for the record, my site is
Not a shameless plug, just trying to give some background.


11-12-2012, 11:30 AM
I remember that I once read a book by Fred Hoyle (Rockets in Ursa Major? - I'm not sure about the title) where he used (I have to translate back from the German version): heliocentric - this was degrees, and astrograde - this was distance from the sun in miles or AU. Then add maybe a third direction - vertical - for distance above or below the system's plane.

11-13-2012, 11:10 AM
If an inhabitant of a rotating planet faces the rising sun, on the left hand will be north, on the right hand will be south. So the four cardinal points could be labelled

Rising (East)
Left, Leftward, Sinister (North)
Right, Rightward, Dexter (South)
Setting, Falling (West)

However, these labels wouldn't work on non-rotating worlds such as tidally locked planets, or on planets which (like Mercury) have a resonant rotation so that the Sun rises in different directions at various times of the year. Nor would they work on stars or black holes. But each of those types of object could have their own distinct set of cardinal points.

11-14-2012, 05:58 AM
Thank you both. These are just the ideas I was looking for. I want the game to feel alien with resorting to cheap alien words "That ship is 5 chakaga's out!" So basically I could say that if your standing at the equator of the rotating body (planet, star, black hole, asteroid) and facing the direction of rotation then:
1) The direction you are facing is called rising because objects in space appear to rise (akin to our concept of east)
2) The direction behind you is called falling because objects in space appear to fall (akin to our concept of west)
3) If Rising is in front of you and Falling is behind you then to the left is Sinister (akin to our concept of north)
4) and to the right is Dexter (akin to our concept of south)

So my compass should look like:

F + R
(sorry the forum does not like erroneous spaces)
Since I can remove the sun from the definitions and refer to any distant point in the sky (star, black hole, pulsar) this is an attractive idea. Are right and left universal terms or would aliens without bilateral symmetry have no such concept? Also, I wonder if on a tidally locked world the stars would still rise and fall? I know the moon still has day and night. Even mercury would observe the other stars rising and falling I would think.


11-14-2012, 03:29 PM
The ideas of chirality and spin direction are definitely universal, and not specific to bilaterally symmetric species like us. While we tend to use left/right terminology for both, you could proceed from the other direction, defining "left" and "right" from spin or chiral terms. Once you've established the baseline terminology (in whatever direction), you can apply them even in cases where your original source no longer applies (e.g. tidally locked planets, stars, black holes, galaxies).

We left/right for chirality because our hands are chiral (mirror images of one another, and thus impossible to transform one into the other through any combination of rotation) - I'm not really sure how a species without such common chiral features would use to define chirality - but there are many possibilities (Wikipedia Chirality (http://en.wikipedia.org/wiki/Chiral)) - though I'd put my money on clockwise/counter-clockwise rotation. I'm also not sure why our hands are chiral from an evolutionary perspective, or whether it would be likely an alien species would develop something similar.

We use it for spin direction partly because of the chirality, allowing us to simply (and universally) specify whether a spin is "up" or "down" - the actual terms are completely arbitrary. As an example, we use the "right hand rule" to determine the spin of the earth - curl your fingers in the direction of spin (eastward) and the direction your thumb points is "up" - or North. The arbitrary aspects unique to our physiology/terminology are "up/North," "east," and "right." Simply substitute your own terms. Notice that galactic directions will also need some sort of up/down-direction component - rimward/coreward, spinward/trailing are two of the three coordinates necessary to specify an object in three-dimensional space. If you prefer spherical coordinates, you'll need an angle from the galactic plane, and if you prefer cylindrical coordinates, you need a height above/below the plane. Given the general shape of galaxies (round and mostly flat), I'd lean toward cylindrical as the most logical choice.

I'd probably use alternative coordinate systems in-system (cylindrical or spherical centered on the star or system's center of mass) or on-planet (cylindrical, spherical, or surface-mapped rectangular). Another potentially interesting development would be if your baseline or primary species were avian or aquatic - they're probably have brains more specialized in conceptualizing 3d systems - humans are notoriously bad at it, since our brains were developed primarily for flat plains.

Tidally locked planets certainly experience standard day/night cycles and rotating starfields, just like any other planetary body. The primary difference is that their "days" are measured in weeks or months. The primary difference when inhabiting a tidally locked planet is that daytime duration - you have to be able to handle the long-term extremes of heat and cold. Imagine living under noon-day sun for 1.5 months, or the same period of time at midnight - that's what it's like on Mercury (if it were conveniently relocated to Earth's orbit). The most common way to colonize such a planet is to start with the poles (which are conveniently located between day/night extremes), though you could try something more exotic (like a traveling colony - maybe mounted on treads (or legs - like the bad-guy city in the John Carter movie), or perhaps flying/floating?

11-16-2012, 02:14 AM
A tidally locked planet does NOT experience day-night-circles: one side (around the "hot pole") is always pointing to the sun, the other (the "cold pole") points away. The system is rotation symmetric around the sun-planet axis, so there is no preferred direction orthogonal to the hot-cold direction. The starfield rotates around the planet once a year (and is not visible from half of it), so I doubt it would figure into cardinal directions.

11-16-2012, 04:14 AM
A tidally-locked world should spin on its axis once a year. The net effect is that one side always faces its sun and that the other side always faces the other way. However, there is still an axis of rotation that defines an equator. The names for directions would still apply here because there is spin that defines an equator, a left (sinister in Latin) pole, and a right (dexter in Latin) pole.

Also, note that these concepts are in no way related to any sort of symmetry of the species living on the planet, just the assumption that they can detect the rising and falling of the overhead star field (meaning relatively clear atmospheres and some sort of EM detection system that can resolve stars through that atmosphere).

Please consider xkcd: Fiction Rule of Thumb (http://xkcd.com/483/) as a cautionary note.