The World of Infinite Sky
Meteography
Although the altitude of any landmass could change over time, Mean Altitude, much like our world's magnetic north, is still the most frequently used altitude reference. It is defined as the altitude matching the official indicator at Kirisame Observatory. While not useful to scientists for advanced work, it is simple and useful for virtually everything else, including aeronautical navigation. Mean Altitude is at the low end of the atmosphere's habitable band and matches up very well with estimations for the overall center of mass of all known land as a whole. Below MA, average temperature rapidly drops and turbulence becomes more frequent. Low altitude areas tend to be cold, non-specifically gloomy and will experience intense blizzards if they are low enough to be engulfed by swells from the Sea of Storms. Above MA, average temperature gradually increases, though altitude cooling dominates local temperatures over land. This means that higher altitude landmasses are more likely to be warm overall but mountain tops are still colder than low lying areas of the same island. Beyond 20-30km above MA, increased fuel requirements reach a significant level, stimying both commercial and military shipping.
Sea of Storms
The lower boundary of the habitable band, the Sea of Storms is an intensely cold atmospheric layer that rises to within 6km of Mean Altitude in winter and retreats to approximately 12km in summer. This is also approximately the altitude of the lowest known land. Land beneath a certain altitude would experience snow and ice buildup exceeding the rate of outflow from thaw and glacial drift and would inevitably be pulled into the Sea of Storms by a feedback loop of mass increase. Most ships want to have as little to do with this layer as possible but some vessels are designed to run in it. For those, the ability to shed ice and negotiate very limited visibility are essential.
The Tropics
The Tropics are a remote layer beginning approximately 40km above MA and continue upwards, ramping up in intensity as one ascends. While this layer can experience intense weather, the greater challenge to ships is producing the lift to get here in the first place. Fuel requirements for altitude increase at an ever greater rate the higher one ascends. A cruiser with weeks or months of endurance at MA could burn up its Luftum supply in a matter of days patrolling the Tropics. Hand in hand with the impact on fuel economy is a marked reduction in the amount of land the higher one goes. Landmass altitude is obviously correlated in some way with the amount of Luftum permeating it. Whether this wealth could be extracted from such remote locations is another matter entirely. Beyond a certain point, there is so little land and habitation that most ships simply aren't built to go there. As a related matter, extraction of Luftum from any landmass naturally lowers its altitude and therefore has a cooling effect on its climate. This has already occurred in some locales with disastrous results.
The Desert
At very high altitudes, water supply becomes a concern. While landmasses in the Tropics have plenty of water, humidity rapidly drops off beyond around 60km above MA and dredging for water with condensations nets becomes virtually impossible. What little land there is becomes increasingly harsh and arid. Some of the highest flying Luftum ships ever constructed were highly specialized tankers and colonial cruisers designed by Continental Powers to operate here. Today, this region of the sky is largely the domain of the airplane.
The Void
High above, beyond even the Desert is the Void. It is too high for even airplanes to reach.
Geography
The Continent
The Continent is by far the largest landmass in the known world. It has a temperate climate, though it was warmer in the past, and has seasons caused by regular atmospheric cycles. Nonwithstanding local variation, there is a slight trend for the land to slope downwards towards the west, thought to be the result of greater concentration of Luftum within the mountains of the Pureland.
While humans have dwelt on most landmasses since prehistory, the Continent is the cradle of civilization. Continental cultures have initiated periodic waves of influence and colonization outwards and it is only recently that the balance of power has shifted in favor of their oldest former colonies. Above the usual political division between countries, there is a tradition of dividing the Continent into five cultural regions – the four cardinal directions and the centrally located Purelands.
Western Plains
The kingdoms of the vast Western Plains have been unified under an imperial banner a few times in the past but found strength despite division during the Age of Luftum. They emerged victorious but diminished and from the Continental Wars and in some cases split into numerous miniscule component states. Now, each wrestles at once with both stability and integrity of what they still hold and the disconcerting notion of reunification in this time of crisis.
Northern Peninsula
A land of many characters divided by small mountain ranges that stretch apart from the mountains of the Pureland. The countries of this region are mostly defeated ones in the midst of reconstruction and turmoil.
Southern Highlands
A rugged land of chasms, caverns and underground rivers. The small countries of the South had their time in the sun during the Age of Sail but have struggled to find relevance in modern times.
Eastern Skies
A huge, roughly semi-circular archipelago adjoining the eastern shores of the continent to form a ring around the Great Gulf. Always more attached to the skies than fellow continental inhabitants, states of the East had been at the forefront of naval technology and imperialism for millennia but has largely been in turmoil ever since the Great Collapse.
The Pureland
The Pureland is a great mountain range that occupies the center of the continent. The Oracle's Mountain lies within it, surrounded by minor states. The people of the Pureland are neutral but well known for their sometimes extreme zeal. As such, they have mostly shunned heavy industrialization.
The Oracle
The seat of the Oracle lies within the dormant caldera of the Oracle's Mountain. It is not the highest of peaks, but its striking, almost perfect cone is certainly among the most visually impressive. The verdant canopy of the Providence Tree hides just beneath the mist shrouded rim. While the oracular tradition has spawned countless shrines with predictive services throughout the land, the Oracle (capital O) perpetually resides in this Valley of Providence and grants audiences only to kings.
Any description of history begins necessarily with the institution of the Oracle which first developed writing. Oracular script was initially developed to transcribe results from prophetic trances and these eventually developed into Mercantic script and Storic script which branched off into all known forms of writing today. Aside from the usual vague prophecies and interpretable predictions, one of the most important powers of the Oracle was (and sometimes still is) to confer kingship.
Near World
The Near World refers generally to lands separate from but fairly close to the Continent – near enough that regular trade has been taking place for centuries or more. The countries in this region are presently the most advanced in the world, having largely overtaken the moribund Continental Powers in effectiveness if not size. Some are former colonies while others are indigenous cultures that have managed to preserve their independence whilst biding their time until today.
Middle Reach
The Middle Reach is the vast halo of lands that have been known since the Age of Sail but only fell into practical reach with the development of Luftum ships. These were the stomping grounds of the Continental Powers during their latter heyday though how much sway they still hold so far out varies from case to case.
Far Shores
Storied lands even in the modern age, the Far Shores are at the limits of reach even for ships powered by modern Luftum turbines. Here exist vast and fabled lands.