Spherical Geometry #4 - Longitudes

Longitudes of the Earth are great spheres passing through the North Pole and the South Pole of the Earth.In the figure shown all the blue lines going from the top to the bottom are longitudes. Longitude is measured as the angular distance east or west between the great circle (or meridian) of the point and the Greenwich Meridian.

Image result for longitude spherical geometry


 It can be measured in degrees as well as hours. It is more convenient to calculate longitude in hours because the time difference between two points on the Earth can be measured easily. Since the Earth takes 24 h to spin around itself once and also that a sphere has to rotate 360° to return to its original configuration, 24 h is equivalent to 360°. So 1 h is equivalent to 15° of the globe.


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