In an effort to help astronauts sleep, the ISS is replacing fluorescent lights with adjustable LEDs, reports

Because the space station circles the Earth every 92 minutes, astronauts on board can see the sun rise and set 16 times in a day. While it might sound delightful to watch pretty sunrises and sunsets all day, this rapid cycle of day and night can throw astronauts’ sleep schedules out of whack. Add to that a demanding work schedule with occasional night shifts, and the astronauts are bound to experience some insomnia.

In fact, research has shown that astronauts don’t get enough sleep. On average, they sleep about 6 hours per night, while their schedules allot 8.5 hours. As a result, sleeping pills and caffeine are popular commodities among space travelers.

On Earth, the human body naturally operates on a 24-hour schedule called a circadian rhythm. Our biological clocks depend on a regular pattern of sunlight and darkness to keep that rhythm going. In space, astronauts depend on artificial lighting to regulate their sleep-wake schedules. But it’s not just the timing of the light that matters on the space station — the type of lights used can make a big difference when it comes to keeping sleep schedules on track.