Name: Michelle L.
Status: Student
Age: 16
Location: N/A
Country: N/A
Date: February 23, 2003
Question:
Why sunrise and sunset times change each day?
Replies:
Michelle,
The Earth is tilted at an angle of 23 degrees from being vertical (as
compared with the orbital plane of the Earth about the Sun).
As the Earth revolves around the Sun during the period of a year, the
northern hemisphere is more pointed towards the Sun in summer and more
pointed away from the Sun in winter.
So, in summer, the Sun rises north of east and sets north of west, giving
it an earlier rise time and a later set time than during the winter when
the Sun rises south of east and sets south of west.
Each day, the times of sunrise and sunset change slightly from the day
before because of the slight change in where the Sun rises and sets.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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