Atlantean Astronomy

Copied from Poul Anderson Appreciation, 29 Oct 2013.

I missed some salient data about Atlantean astronomy in a recent post. The information is scattered through the text(s). I am finding it informative to reread the novelization, Virgin Planet, immediately after rereading the original, shorter, "Virgin Planet." Information is repeated, amplified or nuanced in the longer version.

Atlantis is an Earth-like moon of the gas giant, Minos, which is permanently visible above the colonized hemisphere of Atlantis. When full, Minos is fourteen times the size of Luna as seen from Earth! Also, four other inner Minoan moons may be visible. On one occasion:

"...overhead...were two crescents, dim by daylight: one almost twice the apparent size of Luna seen from Earth, the other half again as big."
(Starship, New York, 1982, p. 97)

I wondered, "Half again as big as Luna or half again as big as the moon that is twice as big as Luna?"

The novel elaborates:

"Overhead...were two crescent moons, dim by daylight, one almost twice the apparent size of Earth's, the other half again as big as Luna seen from home..." (Virgin Planet, London, 1966, p. 31)

The Author's Note to the novel elaborates further:

in full phase, Minos is as bright as twelve hundred full moons on Earth;
the moons Ariadne and Theseus are each several times brighter than Luna;
Aegeus and Ariadne never set but instead move rapidly across Minos from west to east, then behind Minos from east to west;
Aegeus crosses the sky in 3.1 hours and completes its phases in about 30 hours;
occasionally, the full Ariadne changes color as it transits the full Minos at midnight.

What a sky! What might native Atlanteans have made of it? But there are no natives, only colonists. The colony is three hundred years old so its inhabitants are thoroughly familiar with their complicated celestial mechanics - and when a survey man arrives, he knows what to expect.

More could have been done with these ideas. The Author's Note includes information that did not make it into the texts, e. g.:

there are a few primitive mammals on the outer hemisphere but the colonists never see them;
the mountainous main content, on the inner hemisphere, was later named Labyrinth.

After the events of "Virgin Planet," men would arrive, bringing technology. Thus, the colonists would stop reproducing by parthenogenesis, society would modernize and many sequels could have been written about this one planet.