That thick, dismal savage blackness, which Victor Hugo's pen is so fond of occasionally revelling in, surrounded them on all sides and crushed them like an iron shroud.
It was felt worse than ever when, breakfast being over, Ardan carefully turned off the gas, and everything within the Projectile was as dark as without.

However, though they could not see each other's faces, they could hear each other's voices, and therefore they soon began to talk.
The most natural subject of conversation was this terrible night 354 hours long, which the laws of nature have imposed on the Lunar inhabitants.

Barbican undertook to give his friends some explanation regarding the cause of the startling phenomenon, and the consequences resulting from it.
"Yes, startling is the word for it," observed Barbican, replying to a remark of Ardan's; "and still more so when we reflect that not only are both lunar hemispheres deprived, by turns, of sun light for nearly 15 days, but that also the particular hemisphere over which we are at this moment floating is all that long night completely deprived of earth-light.

In other words, it is only one side of the Moon's disc that ever receives any light from the Earth.

From nearly every portion of one side of the Moon, the Earth is always as completely absent as the Sun is from us at midnight.