“Day and night” on the space station

Dear Tom,
I have heard that the space station in orbit around the Earth has huge temperature swings between day and night, but what constitutes “day” and “night” up there?
M. Polansky, Cicero
Dear M.,
“Days” and “nights” at the space station last about 45 minutes. That is the time between sunrise and sunset as the space station, moving at approximately 17,500 miles per hour, moves in and out of the Earth’s shadow. Temperature fluctuations in space are much different than those in the Earth’s atmosphere. There is nothing to change temperatures in space — it’s a vacuum (or nearly so).
In space, objects in shade approach absolute zero (-459.7 degrees F), whereas objects in sunlight broil. That is why objects are made of highly reflective materials to limit heat buildup. Powerful heaters are employed in periods of darkness.

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