During the 1730s geodetic missions, the length of 1 degree of meridian was greater in the polar regions than in the equatorial regions, indicating the Earth can be represented by an ellipsoid slightly flattened at the poles. Which option correctly expresses this finding?

• A. Equatorial regions; Polar regions
• B. Polar regions; Equatorial regions
• C. Polar regions; Polar regions
• D. Equatorial regions; Equatorial regions

Answer: (B)

The length per degree along a meridian depends on latitude because the Earth is not a perfect sphere but an oblate ellipsoid. In such a shape, the meridional radius of curvature grows as you move toward the poles, so a small change in latitude corresponds to a larger arc length near the poles than near the equator. The 1730s measurements found that a degree of meridian is longer in polar regions than in equatorial regions, which fits an ellipsoid that is slightly flattened at the poles (equatorial radius bigger than polar radius). Therefore, the correct expression is that the longer 1-degree meridian length occurs in the polar regions, while it is shorter in the equatorial regions. The other options would imply the opposite pattern or no difference, which contradicts the observation.