Question 1

Why does a flight from Seoul to New York pass near the Arctic?

Accepted Answer

On a flat map the great circle looks curved, but on the globe it is the shortest path, and for northern-hemisphere routes it bends toward the pole.

Question 2

Why use 6,371.0088 km for the radius?

Accepted Answer

It is the mean radius (2a + b)/3 of the GRS 80 / WGS 84 ellipsoid, as recommended by the IUGG.

Question 3

What is the bearing for the return trip?

Accepted Answer

It is not simply the opposite heading; compute it again with the points swapped.

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