Beyond our planet’s atmosphere, the system of timekeeping that gives structure to life falls apart. The words “day” and “night” mean something radically different when you’re completing an orbit of Earth every 90 minutes, as astronauts do aboard the International Space Station (that’s 16 sunrises and sunsets in each 24-hour period).
Since the human body and its circadian rhythms — patterns of sleep and wakefulness regulated by our internal clock — evolved here on Earth, we’re ill-suited for any other environment. In the topsy-turvy world of extraterrestrial time, where astronauts can’t rely on dawn and dusk to keep their usual schedule, they must follow a strict schedule of sleep and work. Any deviation from their natural cycle would quickly lead to physical and mental health problems.
Keeping a Routine in Space
A regimented routine keeps missions on track, so an astronaut’s life in space is almost entirely pre-planned. Activities on the ISS, from meals to exercise to maintenance, are slotted into five-minute increments. And it all must be in perfect alignment with the clocks back home.
“To do what you need to do,” says Todd Ely, a senior engineer at NASA’s Jet Propulsion Laboratory, “you need to be able to tell time wherever you’re at.”
