Why do astronauts see 16 sunrises a day?
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The Sun isn't on fast-forward: the International Space Station circles Earth about every 90 minutes, at roughly 8 km (5 miles) every second. Each lap it flies through Earth's shadow and back into sunlight, so the crew sees about 16 sunrises and 16 sunsets a day. To keep a normal rhythm, astronauts live on a 24-hour schedule set to GMT, and some wear sleep masks to block the light.
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Transcript
- Sef Sixteen sunrises a day? Is the Sun on fast forward?
- Tiggy The Sun is fine. We're the fast ones.
- Tiggy The space station zooms around Earth at eight kilometers every second.
- Tiggy One lap takes about ninety minutes.
- Tiggy Each lap, we fly through Earth's shadow, then back into sunlight.
- Sef Good morning!
- Sef Again?!
- Tiggy About sixteen laps a day. Sixteen sunrises, sixteen sunsets.
- Sef So when do we sleep?
- Tiggy By the clock, not the Sun.
Sources
- NASA: Space Station Facts and Figures nasa.gov
- ESA: Where is the International Space Station? esa.int
- CSA: Sleeping in space asc-csa.gc.ca
- ESA: An astronaut's rhythm esa.int
- NASA: Seven ways astronauts improve sleep nasa.gov
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