This week I ran into an interesting snag as I wrote The Moonstone: How do you keep track of time while you are underground?
Here's the background: Katryl and her companions accidentally wind up in Undercountry, a vast kingdom under the earth whose inhabitants have not seen the sun for a thousand years. There are no days and no nights, no natural wake and sleep cycles, no seasons, no celestial bodies to mark the passage of time--nothing by which we would normally keep time.
Since there are no traditional time-keeping methods, I can not indicate how long my Overdwellers have traveled in Undercountry. "We encountered the water-snake three days ago" just does not compute when there are no days.
So how does one keep time while stuck underground?
This is the idea that I eventually came up with, illustrated by a conversation between Edric, an Overdweller and one of Katryl's companions, and Rory, a Dwarf who has never visited Overcountry:
"That is something I would like to know," Edric said. "How do you measure time here in Undercountry? In Overcountry, we measure time by the dimming and brightening of the light and by the changes of the moon."
What do you think of this idea? Is it believable? Is it clear or do you need more description?
If you have an idea that you think is just killer, let me know!