The world behind the world
Field Notes
Aetheryn is invented, but almost everything in it has a cousin in our world. These notes gather the real science behind its sky and the myths and places behind its realms, with sources, and say plainly where the painting takes liberties.
Why does a rainbow need the sun at your back?
A rainbow is sunlight bent and reflected inside falling raindrops. Every bow is a circle about 42 degrees in radius around the antisolar point, the spot directly opposite the sun, so you see one only with the sun behind you and rain ahead. At sunrise or sunset that point sits on the horizon and half the circle shows. As the sun climbs the bow sinks, and once the sun is more than about 42 degrees high the whole bow lies below the horizon, which is why summer rainbows come early or late in the day.
A second, fainter bow sometimes appears at about 51 degrees, made by two reflections inside each drop, and its colors run the other way, with red on the inside. The sky between the two bows is darker than the sky on either side, a strip called Alexander's dark band.
In the painting
The painting looks toward the sunset, so its sun is behind you only in the morning, and the painted sun shows only once it stands ahead in the afternoon. Aetheryn's rainbows appear after the morning rain or in a sun shower before midday, centered below the horizon by exactly the sun's height and drawn at the real angles, with the secondary bow and the dark band between. When the sun climbs past 42 degrees the bow is gone, so a summer noon never has one. Try Sun shower in Shape the world with the hour soon after dawn.
Sources
Why does the moon change shape, and why is it up at odd hours?
The sun always lights half of the moon; its phase is how much of that lit half faces us. One cycle, from new moon to full and back, takes about 29.5 days. The moon also rises about 50 minutes later each day, so each phase keeps its own hours: a new moon rises with the sun, a first quarter moon at about noon, a full moon at about sunset and a last quarter moon at about midnight.
Around a thin crescent you can often see the rest of the moon glowing faintly. That is earthshine, sunlight reflected from the earth onto the moon's night side. Leonardo da Vinci explained it in the Codex Leicester around 1510. He thought the earth's oceans did the reflecting; we now know clouds do most of it.
In the painting
Aetheryn's month lasts eight fantasy days, so each night brings the next of the eight named phases. The moon keeps the real rising times for its phase, it is lit on the side toward the set sun, and a crescent carries faint earthshine. A bright moon lifts the night and washes out the fainter stars, so the darkest skies, and the most stars, come at new moon. Natural eclipses come only on the new moon day, as real solar eclipses do. You can also choose a phase in Shape the world.
Sources
How do thousands of fireflies flash in time?
In the Great Smoky Mountains, males of the firefly Photinus carolinus flash in bursts of five to eight, then go dark for about eight seconds, and whole hillsides start and stop together. They display for two or three weeks, sometime between late May and late June, beginning at full dark around 9:30 at night. The park is home to 19 species of fireflies, and this synchronized starting and stopping is unique among them. Why they do it is still not fully understood.
Mathematics shows how such order can arise without a leader. In 1990 Renato Mirollo and Steven Strogatz modeled each firefly as a clock that rises toward a threshold, fires and resets, and that is nudged forward whenever it sees another fire. They proved that for any number of identical clocks coupled this way, almost every starting arrangement ends with all of them firing together.
In the painting
Every firefly in Aetheryn runs that model. Each has its own slightly different tempo and flashes five to eight times before going dark, and when it sees a neighbor in its glade begin a burst, its clock jumps ahead. On a summer night the glades start scattered and fall into step within about fifteen seconds; in other seasons the coupling fades and they flash alone, and in winter there are none. The rhythm is quicker than the real one, with about four seconds of darkness instead of eight, so you need not wait as long.
Sources
What colors an aurora?
Auroras begin with the solar wind, the stream of charged particles from the sun. Energy it pours into the earth's magnetic field flows down the field lines toward the poles, and particles strike gases high in the atmosphere, which give off light. Oxygen glows green from about 100 to 200 kilometers up and red above that, while nitrogen adds blue and, lower down, pink or purple.
In the painting
Aetheryn's aurora hangs in folded curtains with a bright hem and rays, and it shimmers in open water. Its curtains fade from green to violet as they rise; real auroras more often turn red at the top, so the violet is a liberty taken for the palette.
Sources
How far away is the storm?
Lightning can heat the air in its channel to as much as 50,000 degrees Fahrenheit, and the air expands so violently that it makes the sound we hear as thunder. Sound covers about a mile every five seconds, so counting the seconds from flash to thunder and dividing by five gives the distance in miles. Thunder carries only about ten miles.
In the painting
Each stroke in Aetheryn carries a distance, and its thunder is delayed in proportion. Strokes are at least six seconds apart and never flash more than twice in any second, below the three flashes a second that accessibility guidelines warn against, and they stop entirely when motion is paused.
Sources
Where do sunbeams come from?
Crepuscular rays are the bright and dark strips that cross the sky when clouds or mountains block part of the sunlight. They show best against a sky that contrasts with the light, as when rain clouds shade one part of it.
In the painting
Aetheryn draws its shafts of light the way many games do. For each point on screen it steps back toward the sun or the crystal core and gathers the bright parts of the scene that nearer forms do not block, so the rays break around towers, branches and isles.
Sources
In our world, realm by realm
Each realm's page ends with notes on the myths, places and science it echoes.
- IThe World TreeThe tree at the center of the Norse worlds · Crystals large enough to walk along
- IIThe Skyward IslesLaputa, the flying island · Stone pillars in the clouds
- IIIThe Frozen CitadelA palace of ice on the Neva · Why deep ice glows blue
- IVThe Sapphire LagoonWhy shallow water turns turquoise · Lakes that build their own dams
- VThe Lantern GardensLanterns for the first full moon · A garden that may have stood elsewhere
- VIThe River of LifeThe river of five colors · A bridge made of rainbow
- VIIThe Ember ReachTwo kinds of lava, two Hawaiian words · Lakes of lava and storms of ash
- VIIIThe Gilded CityEl Dorado was a person before it was a city · Why the light turns gold
Written for Aetheryn 1.3 in October 2026 from the sources listed with each note. The realm names and their lore are invented for the painting; these notes are not.