Twenty-four hours equals one day and night on Earth, the length of time it takes the Earth to rotate once on its axis.

When the Earth spins around on its axis, it creates night and day on Earth.  This movement makes it look like the Sun is moving across the sky.  The Sun rises in the east and sets in the west, turning day into night.

Most places on Earth have some amount of day and night every 24 hours.  On Earth, the length of day and night usually changes with the seasons.

To astronauts orbiting the Earth from space, viewing day and night is quite a surprise.  “The views from space are pretty spectacular,” said astronaut Rex Walheim, who performed two space walks on his first flight in April 2002. “I could see from Wyoming all the way to Southern California.” Walheim was amazed at how blue the ocean looked from space. Owen Garriott is another astronaut who has walked in space. He performed three EVAs during the second manned Skylab mission and compared the view to looking “down this very long elevator shaft” to the surface of the Earth. “It’s quite an interesting view,” he said.

One of the things that surprises astronauts most is the rapid alternation of day and night as they orbit the Earth. They make a complete orbit every hour and a half. “The lights keep going on and off every 45 minutes,” Walheim said. Herrington added that without the filter of the Earth’s atmosphere, the days had a “brilliant white light and the nights were incredibly dark.”