Sunita Williams Sees 16 Sunsets Daily in Space—Here’s Why

Astronaut Sunita Williams witnesses 16 sunrises and sunsets every day due to the rapid orbit of the International Space Station (ISS) around Earth. As the ISS travels at a speed of about 17,500 miles per hour, it completes an orbit roughly every 90 minutes, allowing Williams to experience multiple sunsets within a single 24-hour period.

NASA astronaut Sunita Williams has the rare opportunity to observe 16 sunrises and sunsets every day while aboard the International Space Station (ISS). In 2013, Williams shared, “After working hard to reach space, I was fortunate to experience 16 sunrises and 16 sunsets each day aboard the swiftly moving space shuttle.”

How Do Multiple Sunrises and Sunsets Occur?
The ISS completes an orbit around Earth every 90 minutes, traveling at approximately 28,000 km/h. This means astronauts witness a sunrise or sunset every 45 minutes. In a single Earth day, astronauts aboard the ISS experience 16 full cycles of day and night. The ISS moves at a much faster pace than Earth’s day-night cycle, where each day typically lasts around 12 hours. As a result, astronauts transition between light and darkness every 45 minutes, experiencing a unique cycle that repeats 16 times within 24 hours.

How Do Astronauts Know When to Sleep?
Astronauts adhere to a schedule based on Coordinated Universal Time (UTC) due to the absence of regular day-night cycles in space. Their day is broken into approximately 5-minute segments for work, exercise, meals, and rest, a routine that helps maintain both mental and physical health. On Earth, humans use the rising and setting of the Sun as natural cues for sleep and wake cycles. However, in space, astronauts don’t have these cues since the Sun doesn’t rise or set in the same manner. Consequently, the ISS’s continuous motion requires a fixed schedule, and astronauts follow UTC to maintain balance in their routine while managing the demands of space life.

Astronauts also rely on accurate atomic clocks to stay in sync with Earth-based teams, which is crucial for navigation during deep-space missions.

Sunita Williams, who has been aboard the ISS since June 2023, experienced delays in her return to Earth due to issues with Boeing’s Starliner. She is now expected to return in February 2025 aboard SpaceX’s Crew Dragon.

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Source: MSN‍