What space travel teaches us about sleep and circadian rhythms

What space travel teaches us about sleep and circadian rhythms

On Earth, most of us rarely have to think about the signals that keep our internal clocks aligned. The Sun rises, daylight changes, darkness arrives and morning comes again. Our bodies have evolved alongside this roughly 24-hour cycle. Light is one of the strongest signals our bodies use to synchronise the circadian clock. But what happens when the Sun no longer provides a reliable schedule? A spacecraft orbits Earth roughly every 90 minutes, so…