Possibly many of you will have traveled by plane at some time and to reach your destination, you have made a very unusual detour.
Why has the plane made this deviation and has not gone in a straight line? Is not the straight line supposed to be the shortest distance between two points?
Well, in this post we will learn that this is not always the case.
The line that covers the shortest distance between two points is called geodesic. And this line does not have to be a straight line.
The geodesics of a flat surface are straight. Therefore, in short distances, or on paper or any Euclidean surface, the shortest distance between two points is a straight line.
That is, a Euclidean space is any space that is not curved. For example a folio or a square.
The earth has a spherical shape, so more or less, we can apply its same properties.
In a sphere, the geodesics correspond to the lines that pass through the center of the sphere and divide it into two equal hemispheres. These lines are called maximum circles. In reference to the Earth, it would be the equator and the meridians.

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Knowing this already, on Earth or any sphere, the shortest distance between two points is the line that passes through those two points and divides the sphere into two exactly equal hemispheres. There is always at least one.
For this reason, to go from Madrid, Spain to Mexico, you go through Canada and very close to Greenland. The shortest routes to join two points depend a lot on the shape of the surface, because as we have already seen, the shortest route in a plane, a sphere or a polyhedron is not the same.
There are other factors for airplanes to follow their routes, such as the distance to the minimum airports they have to be in for emergencies, the restrictions of air spaces and air currents.
I hope you liked it and you can go to sleep today having learned a new thing. Thanks so much for reading :)

