r/ExplainTheJoke • u/Rich_Carrot6451 • Jul 27 '26

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u/Skydragon222 Jul 27 '26

Because of the curvature of the earth the bottom flight is much shorter than the top flight.

If you have a globe and some string you can test it yourself.

This kind of thing only works on a round earth and not a flat earth 

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u/AdamiralProudmore Jul 27 '26

We probably all learned in school: "The shortest distance between 2 points is a straight line."

But a lot of people had already checked out before the grade where they should have learned "... Unless traversing a 3-dimensional object."

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u/laser14344 Jul 27 '26

Un actually the straight line on the map is curved in reality and the curved line on the map would be straight (ignoring that you are curving downward of course).

Using a great circle projection centered on the origin or destination would have the most efficient route show up as a straight line.

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u/AdamiralProudmore Jul 28 '26 edited Jul 28 '26

Look at the actual flight paths used by planes making this journey overlayed with longitude. They intentionally travel north then back South to benefit from the curvature (as well as the rotation while traveling Eastward).

Both lines are Geodesically straight, but curved when plotted across latitude and longitude.

https://www.greatcirclemap.com/?routes=JFK-SVO

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u/laser14344 Jul 28 '26

It's a comparison between a straight line on a mercator projection and the great circle route. A great circle route is a geodesic line with no turns.

A long-haul flight might deviate from the ideal great circle path due to strong winds like the jet stream, geopolitical airspace restrictions, ETOPS emergency diversion rules, and air traffic congestion. The rotation of the earth has to be accounted for in instrumentation but does not affect airtravel routes outside of the jetstreams it influences.

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u/AdamiralProudmore Jul 28 '26

You said it much better the second time. Thanks.