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Since the whole idea is to simulate Terrestrial conditions as much as possible, the cardinal directions within the cylinder should reflect those found on the Earth. How do you map the compass points of the exterior of a sphere to the interior of a cylinder? You use an easy-to-remember rule of thumb—and remember that it’s all done with mirrors.
Nearly everything in the Solar system revolves around the Sun in the plane of the ecliptic—and rotates on its axis within that orbit—in the direction that we call counterclockwise. This counterclockwise orientation is so universal that the few bodies (the planets Venus, Uranus and Pluto, about half of the Jovian outer moons, the Saturnian moon Phoebe and the Neptunian moon Triton) that do not conform to it are usually referred to as having “retrograde” motion—they’re literally moving backward relative to everything else.
We call this direction counterclockwise because the first clocks were sundials and the time was read by watching the shadow of the gnomon, which of necessity moves conversely opposite to the apparent motion of the Sun. The Earth revolves counterclockwise around the Sun and rotates counterclockwise on its axis. The Sun appears to rise over one side of the horizon as the Earth turns to face it and to set beyond the opposite side of the horizon as the Earth continues turning to face away from it. (My Gaelic ancestors coined the word deosil to describe the act of traversing a circle to right, emulating the movement of the Sun, and widdershins, traversing a circle to the left. Both words are still used today by my modern Paganist friends, to whom I say “Blessed Be!”) We call the direction of the apparent sunrise “east” but it would be more accurate to call it counterclockwise or “downspin” (spinward, the direction toward which the Earth is spinning). “West” is clockwise or “upspin” (antispinward, the direction from which the Earth is spinning). “North” is toward the axis of rotation and “south” is away from the axis of rotation—until you reach the equator, at which point the situation becomes reversed, with south being toward the axis of rotation and north being away from it.
The terminology we use to orient ourselves here on the Earth is therefore somewhat arbitrary, being a consequence of the fact that civilization as we know it originated in the Northern Hemisphere. The word “orient” is itself a reference to the convention of using the direction in which the Sun rises as a starting point to determine the cardinal directions. The Boy Scouts of America still teach the ancient rule that, when you face east (toward the sunrise), north is to your left and south to your right. When you face west (toward the sunset), north is to your right and south to you left. You may not have a compass and may not be able to find north, but the Sun will always appear in the east and disappear into the west. Keep this spatial orientation in mind, because it’s the key to understanding everything else. Had the Incas of South America or the Zimbabwe of South Africa or the Polynesians of the South Pacific become the great world powers instead of the Asian, European, Mediterranean and North African civilizations, our spatial orientation would be the reverse of what it is now. Maps would be upside-down, seasons would be reversed and clocks would run backward relative to the familiar Eurasian-centric, northern hemispheric orientation that has become the universal norm throughout the world. But it’s no accident that the people of the Northern Hemisphere became the great world travelers and explorers, and subsequent traders and conquerors, while those of the Southern Hemisphere lagged behind. They had the advantage of an aid to navigation that their southern counterparts lacked: an apparently fixed “pole star” that literally pinpointed “true north” and gave a direct and immediate visual indicator of the Earth’s axis of rotation!
This is where the “rule of thumb” comes into play. It’s a variation on the Right Hand Rule used in a number of scientific disciplines to help determine angular, rotary and vector relationships. Make the “thumbs-up” sign with your right hand. Your fingers form an counterclockwise circle, with the fingertips indicating the direction of rotation. Your thumb points along the axis of rotation. You have just created cardinal directions, with your fingertips indicating east and you thumb indicating north, with their antithetical west and south in the opposite directions. Extend your index finger perpendicular to your thumb and it will point along the line of flight (a tangent to the orbit of the Earth around the Sun). Extend your middle finger perpendicular to both thumb and forefinger and it will point toward the focus of the orbit, in this case the Sun itself. But space colonists don’t live on the exterior of a rotating sphere, they live on the interior of a rotating cylinder. To apply this rule of thumb to a space colony at all, you must map these directions onto a cylinder, formed by the curl of you fingers. Rotate your hand until your thumb points at your face and you can look through that cylinder. Your thumb now indicates the direction toward the Sun and your index and middle fingers point along the line of flight and down toward the focus of the orbit, respectively. If your face were the Sun, rays from your eyes reflecting off an angled mirror projecting from the back of your hand and down into the cylinder formed by your curled fingers would illuminate your fingertips in the same fashion that sunlight illuminates the interior of a cylindrical space colony. But there’s a problem. Our hypothetical Boy Scout facing east (downspin) will find the direction previously identified as north to his right, not his left. That’s because he lives in a inverted world that is literally a mirror-image of the Earth. In order to map the directions correctly, we must reverse them. We must apply a Left Hand Rule, the mirror image of the Right Hand Rule. The colony must be given a retrograde motion, rotating clockwise around its axis in a clockwise orbit around the focal point. Give “thumbs up” with your left hand and you will see that your thumb still indicates true north and your middle finger the focus of the orbit, but the direction of rotation and line of flight have been reversed.
The resulting cardinal directions within a space colony are downspin (east), upspin (west), port (north) and starboard (south). East is “downspin” because that’s the direction in which the world turns. West is “upspin” because it’s the direction opposite east. North is “port” because it’s to your left (on the port side) as you face downspin, the same way you find north on the Earth. (It’s also literally the port side, because the primary docking port bay block is on the side facing the Sun.) South is “starboard” because it’s the direction opposite port, facing away from the Sun and hence toward the stars. “Up” is, of course, inboard toward the central axis; “down” is outboard toward the cylinder wall.
Please note that all of this is only true for the single, independent colony cylinders depicted in the Gundam animation and artwork. In an actual O’Neill “Island Three” habitat, consisting of a pair of counterrotating ballistically coupled cylinders, the scenario described here would only apply to one of the cylinders, which might be called the “lefthanded” or sinestral cylinder. The other cylinder, which might be called the “righthanded” or dextral cylinder, would be the mirror image of its mate. It would therefore spin in the opposite direction, counter-clockwise, so the cardinal directions would be reversed and the neat correspondence to the Terrestrial map would no longer apply.
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