Later, near the Shield Wall, Jessica and Paul sleep during the day (presumably hours) to wait for nightfall.Leto stood in the foyer of his house, studying a note by the light of a single suspensor lamp. Dawn was yet a few hours away,
Sounds like the day and night are each several hours long. A normal day/night cycle.He had awakened shortly before nightfall, sitting up in the sealed and darkened stilltent.
Now, both Arrakeen and the Shield Wall are north of 60 degrees latitude. I guess somewhere between 65 and 70 degrees North.
On the Earth, at these high latitudes, the day is almost 24 hours long during the summer, and during winter the night is almost 24 hours long.
This happens because the Earth's axial tilt is 23 degrees and during summer everywhere within 23 degrees of the pole is permanently pointed at the Sun.
That means for Arrakis to have normal hours during day and night at high latitudes, the axial tilt must be close to zero . But close to zero axial tilt also means no seasons.
Yet, seasons are mentioned in the books. Some examples:
Frank Herbert in DUNE wrote:"Those are date palms," he said. "One date palm requires forty liters of water a day. A man requires but eight liters. A palm, then, equals five men. There are twenty palms out there--one hundred men." "But some of those people look at the trees hopefully." "They but hope some dates will fall, except it's the wrong season."
Frank Herbert in DUNE wrote:Dawn's gray line behind them was brightest at the notch in their horizon-calendar that marked the middle of autumn, the month of Caprock.
So, has anybody read something about this, that could explain the discrepancy?Frank Herbert in GEOD wrote:With First Moon almost directly overhead, it was quite light in the forest and, although these were the higher latitudes of Arrakis it was still warm from the heat of a summer day