Astronauts face sleep challenges due to rapid orbital sunrises and sunsets
Scientists explain how astronauts in orbit experience frequent day-night cycles that disrupt normal human circadian rhythms.
Orbital environment disrupts natural cycles
A spacecraft orbits Earth roughly every 90 minutes, causing astronauts to see about 16 sunrises and sunsets within a single day. This rapid cycle prevents bodies from using sunlight as a reliable signal for sleep schedules. Consequently, the internal clocks that regulate daily activities struggle to align with the environment outside the vessel.
Two biological systems interact
Sleep is controlled by a circadian clock and a separate system known as sleep pressure that builds during wakefulness. These two systems usually work together to determine when a person should rest or stay awake. External factors like jet lag or shift work can pull these interacting systems apart.
Spaceflight tests human biology
Researchers view spaceflight as an experiment that reveals what happens when environmental cues for sleep disappear. Astronauts may feel exhausted after long periods awake yet still struggle to fall asleep due to circadian misalignment.
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