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Name: Linda K.
Status: Teacher
Age: 50s
Location: N/A
Country: N/A
Date: July 2001


Question:
What parallel has half the circumference of the Equator?



Replies:
Linda,

This question is similar to one that I answered before, but with a specific latitude twist.

The circumference at the equator is pi (3.1416) times twice the radius (r) of the Earth.

To find the latitude that you want, take half the circumference at the equator (2 X pi X r/2). We now have to find the cosine of the latitude angle that equals 0.5 (r/2 = 0.5 X r). Either by trial and error or by using arccos, we find that the latitude where the circumference is half that at the equator is 60 degrees.

David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory


If the earth were a perfect sphere, it would be 60°. Since the earth is slightly flattened at the poles and bulging at the equator, 60° has a circumference slightly less than this. So, the actual latitude will be slightly lower than 60°, but I do not know the exact number for sure. Since the "oblateness" of the globe is quite small, however, the answer to your question is very close to 60°.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois



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