There is no artificial control of day and night on the spaceship Brave. Everyone can rest freely after completing their work according to their personal schedules, and to these research fanatics, eight Earth hours is considered very sufficient rest time.
To make himself appear as normal as possible, Wang Zhifan deliberately went to rest for a few hours, even though his body did not need it.
He slept in a very inconspicuous little cubicle in his office. If he hadn't specifically looked up where his bedroom was in the database, he might not have believed that a place that looked like a convenient spot for catching up on sleep would be a legitimate bedroom. This shows that although the Brave is very large, its use of space is quite precise.
