The clock of the orbits · measured, not derived
Tabla de Fases
En quelques mots
The Tabla de Fases is the list of measured orbits that everyone in the Aurin system navigates by. It is needed because the moons go round far faster than their masses allow, and nobody knows why. The Pathfinders, the explorers’ guild, measure it, and CUADRANTE, an old navigation core from the fleet, keeps it.
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It is the first thing a pilot learns and the last thing an engineer accepts.
What is the Tabla de Fases?
The Tabla de Fases is an empirical ephemeris: a table of where each body in the sky will be, built by measuring rather than calculating. The Pathfinders, the explorers’ guild, measure it body by body. They keep it up to date without ever claiming to explain it. Its principle fits in three words: measured, not derived.
In Aurin, the settlers’ system, no one works out trajectories from masses. They consult the Tabla.
What is strange about Aurin’s sky?
The moons move too fast. Selvane, a moon of Ithera, goes round the planet once every two hours. Given its mass and its distance, the laws of orbital motion say it should take almost a month.
Each body’s gravity does match its size and density (see El Lastre). What no one can explain is the motion. The moons complete their circuits in hours where the laws of orbital motion, with the measured masses, call for days. And yet, within each family of moons, the relationship between distance and period is as exact as clockwork.
Three schools of scholars argue over it. All three accept the gravity; what they argue about is that clock.
Which moons keep an exact rhythm?
First, who goes round whom:
- Ithera: Melvara, Tirane and Selvane.
- Kharsis: Kravane, Kharun, Erran and Ashkar, a captured asteroid.
- Kaldrek: Renvar and Ordrek.
Two trios form exact 1:2:4 Laplace chains: Melvara, Tirane and Selvane, and Kravane, Kharun and Ashkar. While the slowest of each trio goes round once, another goes round twice and the fastest four times.
- Both chains close to the last digit.
- Their phase relationship forbids all three moons from lining up at once.
- The three around Kharsis always rise and set at the same point on the horizon. The miners have used them as a clock for forty years without ever correcting it.
Renvar and Ordrek cross over the same point of Kaldrek’s ring every three orbits of Renvar. It is a 3:1 resonance you can predict with a pencil.
Which moon follows no one?
Erran, la Errante. It orbits Kharsis outside the chain, with its axis tilted thirty-one degrees. Its rising point sweeps the whole horizon over a season, and no two of its dawns are alike. It is the only moon where surface navigation cannot be learnt by heart. The miners do not trust it.
Who keeps it?
The celestial mechanics the Flota Aura, the settlers’ fleet, brought with it are no use here at all. Only the Tabla works.
It is kept by CUADRANTE, one of the compis, the fleet’s auxiliary cores that were rescued. He is the navigation core. The Pathfinders recovered him from Puerto Aurora, the eight-dock port built on Tirane for the Arca Aurora. His dossier sums it up: “He doesn’t calculate it: he remembers it, compares it and calls out the solution.”
It speaks with an old-fashioned courtesy and gives figures. If asked about La Cicatriz, the furrow the Arca Aurora left on Ithera when it crashed, it changes the subject with great elegance.
Why doesn’t everyone accept it?
For an engineer trained in the Flota, the Tabla is a defeat: a table of data where there should be an equation. A pilot, by contrast, learns it before anything else, because it is what gets them home. The archive records the disagreement and leaves it unresolved.
