# how airplanes fly.

**URL:** <https://boards.straightdope.com/t/how-airplanes-fly/847658>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [February 9, 2020, 1:51am UTC](https://boards.straightdope.com/t/how-airplanes-fly/847658 "2020-02-09T01:51:10Z")\
**Posts on this page:** 1\
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**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\
**Post date:** [February 12, 2020, 4:35pm UTC](https://boards.straightdope.com/t/how-airplanes-fly/847658/24 "2020-02-12T16:35:27Z")

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> [@DesertDog](#):
>
> The Bernoulli hyothesis sounded like BS to me when I learned it in my teens. Sure, the faster moving air reduces pressure to cause lift; you can prove that by blowing air through a straw held over a piece of paper. The question I had was _why_ the air is moving over the top of a wing faster just because it has a longer path – were the molecules that got split having conversation and the one on top wanted to continue it?

I always took this to be a manifestation of the [continuity](https://en.wikipedia.org/wiki/Continuity_equation) [principle](https://en.wikipedia.org/wiki/Continuity_equation#Fluid_dynamics). See [here](https://en.wikipedia.org/wiki/Euler_equations_(fluid_dynamics)) for more detail. If the molecules that take the longer path didn’t catch up to those that took the shorter path, you’d end up with a mass imbalance.

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