As man begins to think in greater terms than those bound to the soil of the earth, the known directions of North, South, East and West become insufficient terms for referring to directions within the galaxy. Instead, the following conventions have achieved widespread acceptance when referring to direction:
- Coreward refers to the direction of the galactic core, the centre of the galactic coordinate system. On the Imperial coreward frontier lie the Vargr Extents, populated by the Vargr, decendants of earth's canine stock and uplifted by the Ancients eons before the rise of the Third Imperium.
- Rimward is the opposite direction from Coreward, refering to the direction away from the Galactic Core, towards the galactic rim. To the Imperium's Rimward Frontier lies the Solomani Confederation, a polity of humans from Earth, which keeps an uneasy peace with the Third Imperium. What lies beyond is currently unknown by Imperial scientists, as the Solomani keep their exploration data to themselves.
- Spinward refers to the direction of the Galactic Spin, i.e. the direction the galaxy is rotating to. On MegaTraveller starmaps, Spinward is mapped on the lefthand side of the map. In that direction from the Third Imperium lies the Aslan Hierate, a large polity populated by a race feline aliens, and the Claw, a large starless area, which forms a natural barrier to expansion. However, the Imperium managed to settle a large area Behind the Claw, the Domain of Deneb (later The Regency). The most spinward sector of this Imperial Domain are the Spinward Marches, which border the Zhodani Consulate and the Vargr Extents to Coreward and the Sword Worlds to Spinward.
- Trailing, the final of the four galactic directions used in Traveller, refers to the direction against the Galactic Spin, i.e. the direction contrary to the galaxy's movement around it's own axis. Trailing is usually mapped on the right hand side of the map. Trailing of the Third Imperium lie the Empires of the militant vegetarian K'Kree, a race of intelligent grazers who had to stave off a second intelligent race early in their evolutionary development, and of the Hiver, the most alien of all known Major Races in Traveller, pacifist multilegged/armed manipulators without a vocal language.
Terry Pratchett's Discworld:
This world, being a disc and thus without a north pole, uses similar directions: Coreward becomes Hubwards (towards the center point), Rimward remains, Spinward becomes Turnwise (as the Discworld turns slowly on the backs of its carrying elephants), and finally, Trailing is called Widdershins.
Other SciFi Universes might use different naming arrangements. If you know any, let me know so I can expand this wu.
These directions are all based on two-dimensional science fiction universes, where the galaxy is a flat disc. In real life, with the galaxy having a given thickness, two further directions are needed, which could be named Up (towards Andromeda) and Down (opposite). Wolfdave suggests an even better solution: define Galactic North as "The direction from which, when viewed at a sufficient distance and at 90 degrees to the Galactic Equator, the Galaxy appears to be rotating anti-clockwise". This is similar to the definition used to determine north and south on other planets in our solar system, and has the advantage that it doesn't need an Extra-Galactic reference point.
If we ever get to other, irregular galaxies, such as the Magellanic Clouds, we may need to find yet another way to define galactic directions, and yet another would be needed for inter-galactic journeys (which fix point should we use for these?). But those things are still a couple of millenia away, so we best start thinking about crossing these when we get them.
At this point, however, the next step for humaniti
(sic) is to explore the Solar System, and lucky for us, the same directions used on a galactic scale would also work within our Solar System. Coreward would become Sunward
(since the Earth moves around the Sun
, remember?), Rimward could either remain or become Beltward
, Spinward and Trailing would remain. As there is no real need to leave the general plane, Up and Down would not be needed on a larger scale, either...