The International Space Station (ISS) presents a unique challenge when it comes to maintaining a sense of normalcy and structure for its crew members. With the ISS completing an orbit of Earth every 92 minutes, resulting in 16 sunrises and 16 sunsets per day, the question of when to sleep, pray, and celebrate birthdays becomes a complex philosophical dilemma. The crew's daily schedule, which includes designated wake times, work periods, and sleep periods, is crucial for their well-being and performance. However, the human body's natural circadian rhythms are disrupted by the constant light-dark cycle in space, leading to erratic melatonin secretion, drifting core body temperature, and flattened cortisol patterns. To combat this, the station's lighting system is designed to simulate the dawn-to-dusk gradient, providing a daily prescription of photons to help the crew maintain their circadian rhythms. Sleep is another challenge, as astronauts typically get less sleep in orbit than the recommended 7-9 hours. The crew's sleep stations, which are roughly the size of a phone booth, are fitted with sleeping bags tethered to the wall, a laptop, ventilation, and a door that closes. This tethering is necessary to prevent the crew from drifting into equipment or other crew members while sleeping. Despite these challenges, the crew insists on celebrating birthdays, holidays, and other rituals, which are essential for maintaining a sense of normalcy and meaning during their time in orbit. The ISS has proven that human beings cannot live in raw orbital time without the structures and markers that make time feel like a place rather than a current. The crew's daily schedule, lighting system, and sleep protocols are all carefully engineered to help them maintain their circadian rhythms and overall well-being during their time in space.
