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  • The earth spins once per day which means that if you live at the equator,

  • the surface of the earth with you on it is moving around a thousand miles per hour to the east relative to the center of the Earth.

  • Even at 45 degrees latitude, the Earth's surface is moving 700 miles per hour to the east.

  • So it kind of seems like it should be faster for airplanes to fly west.

  • I mean their destination is literally spinning towards them.

  • At the same time, however, they're spinning away from their destination.

  • When we say the earth is going a thousand miles per hour to the east

  • that means that the ground, and airplanes on the ground, and even the air above the ground are also moving a thousand miles per hour to the east.

  • For an airplane to get anywhere, it has to start moving relative to the ground and through the air, at something like a hundred or so miles per hour.

  • So when it flies east, it's actually moving a thousand plus a hundred mile an hour to the east.

  • And when it flies west, it's actually moving a thousand minus a hundred miles an hour to the east

  • Yes! To go west, you go east just slower than the Earth is going east.

  • Unless you're within 10 or so miles of the poles in which case a brisk westward walk will take you legitimately west.

  • That said a plane do often take different amounts of time to fly the same route in different directions.

  • Because of wind in the upper atmosphere like the jet stream that they either have at their tail or have to fly into.

  • The prevailing direction of these winds is largely caused by the Coriolis effect,

  • which is caused by the fact that different parts of the Earth are moving east at different speeds,

  • which happens because the Earth is round and spinning.

  • So airplane travel times are influenced by the rotation of the Earth, just not in a straightforward way.

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  • I highly recommend the book K2 by Ed Viesturs and David Roberts,

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The earth spins once per day which means that if you live at the equator,

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