Light imagery plays a major, recurring role in the book. We frequently get descriptions of different kinds of light, most notably the glaring lights of the prison compound and the natural light of the sun and the moon. Both sets of lights play different roles in the life of the zek:
Two big searchlights from watchtowers in opposite corners crossed beams as they swept the compound. Lights were burning around the periphery, and inside the camp, dotted around in such numbers that they made the stars look dim. (36)
The lights of the camp are numerous, harsh, and controlling. They are there to reveal zeks to the eyes of the guards, and the zeks are basically under constant surveillance day or night. What's interesting here is that the lights are so bright that they even "dim" the stars. In a way the prison camp lights interrupt normal patterns of day and night. This fits in with another motif that crops up along with the light motif: time and clocks.
Zeks aren't allowed to own clocks, and the guards tell time "for them." In a sense, the prison uses lights to control not only the zeks but also day and night and time more generally. The zeks can only tell time by natural light, the sun or the moon, which the prison camp lights often drown out rather symbolically. Throughout the text, Shukhov makes note of the position of the sun and the moon, since it's his only way to tell time on his own. The frequent mentions of the sun and moon also help to emphasize how insanely long a zek's day is. Shukhov gets up when it's still dark and he doesn't get to leave the worksite until after the moon has risen.