The world represents a strong motif in Night with many occurrences. An early metaphor--which is a comparison between two unlike things--describes the world as a "hermetically sealed cattle car." A hermetic seal is one that is airtight. A cattle car, of course, is a train car that is used to haul cattle. The metaphor incorporates a paradox and an irony.
The world had become a hermetically sealed cattle car.
It is ironic that a cattle car would be airtight because the point of shipping cattle in a special freight car is to make sure they have plenty of air so they arrive at their destination alive and only a little the worse for the trip. The paradox is that train freight cars for keeping cargo alive might be sealed and crammed full for letting humans die.
The idea of a hermetic seal becomes a silent theme that runs through the continuing motif of the world. The hermetic seal provides the unspoken answer to the questions asked about the world: each of the following questions may very well be answered with "because the world too is hermetically sealed and kept away from truth ....":
How was it possible that men, women, and children were being burned and that the world kept silent? No. All this could not be real ....
The world would never tolerate such crimes. "The world? The world is not interested in us. Today, everything is possible ...."
Those whose numbers had been noted were standing apart, abandoned by the whole world. Some were silently weeping.
Elie compared the world to a cattle wagon, hermetically sealed.