I’ve never understood how this battle could possibly persist, considering that planes can fly upside-down. The fact that Bernoulli’s Principle creates a low-pressure zone on the top of the aerofoil just gives you laminar flow at higher angles of attack.

It really isn’t that mysterious, unless you insist that only a single physical law is allowed to come into play.

> I’ve never understood how this battle could possibly persist, considering that planes can fly upside-down.

That's orthogonal. Planes flying upside down still have air flowing faster over the new "top" of the wing than the bottom.

Though, a common misunderstanding is that air must be taking the same "time" to go over the top and the bottom. This is not true.

You can build a pretty good mental model of flight with either simplified mechanism, but you end up underestimating performance by a fair bit.

> You can build a pretty good mental model of flight with either simplified mechanism, but you end up underestimating performance by a fair bit.

I've never hear of a good mental model built on Bernoulli's Principle. They are either:

- Wrong

- Give no intuition

The key question is /why/ air moves faster on one side, and once you get away from the misconception of same time, I've never heard an intuitive argument.

Redirecting air down:

- makes complete sense

- can be demonstrated by sticking your hand out the window of a car

- works with flat airfoils (sails, kites, etc.), and explains those well too

And the shape of the wing comes in from wanting the leading edge parallel to incoming airflow, and the other edge parallel to outgoing airflow. On a sail, I can adjust the shape. On a steel wing, I can't much, so I make a shape which works across different angles of attack.

All of the other mechanisms, you can gradually work in from there to get accurate models. Toss in air moving to the low-pressure area, and having momentum, and you get why helicopters are less efficient than planes, as well as vortex shedding. It all builds up.

As a corollary, Bernoulli tells you where air moves faster, but that follows from lift. Not the other way around. At least in any model which fits the human brain.

Why are you benchmarking models to human intuition? If you apply the same reasoning to quantum mechanics you'll have a bad time.

I'm sure models can accurately compute how much of the wing lift comes from the suction effect on the top of the wing versus the push on the bottom of the wing.

Because it's literally what I'm responding to:

"You can build a pretty good mental model of flight with either simplified mechanism"

For computational models, neither of these are great starting points. When I last looked, finite element methods were where the action was.

And if you don't apply the same to quantum -- looking for intuition -- you'll have a bad time. Quantum computing algorithms came from human insight.

> The key question is /why/ air moves faster on one side, and once you get away from the misconception of same time, I've never heard an intuitive argument.

Since the air follows a curved surface instead of straight ahead, you could perhaps apply your intuition for centrifugal force. Momentum sort of pulls the air away from the surface.

I’m not even sure this explanation is wrong.

That's interesting.

Counterpoint: A wing with the opposite curvature would work too, just much less efficiently. Your explanation has an element of truth, but an element of untruth. It'd take more analysis to tease them apart.

In the Vsauce video "Do Chairs Exist?" (I highly recommend it!), Michael talks about the concept of vagueness and how defining boundaries can lead to paradoxes. While it was primarily dealing with an ontological perspective, the linguistic perspective of a particular line has always stood out to me. Perhaps it makes a bit more sense in context of the full 40-minute video, but it is:

>"Composites are causally redundant. Believing in chairs is like believing that, while yes, the burning gas from my stove completely describes why the water in a pot boils, there’s ALSO a magical invisible substance called boil-o that comes out of my stove that does the same thing as the flame at the same time, and if there was no boil-o, the flame would warm the water just the same, but there IS boil-o... Chairs are no more real than boil-o. Composites over-determine what happens in the world."

Like your example with lift and fluid dynamics, simple explanations like "plane pushes air downwards" or "faster flow sucks the plane upwards" might be insufficient, but they're at least useful to the layman. It also reminds me of how Richard Feynman answered the question, "What is the feeling between 2 attracted magnets?" by explaining that it would be impossible to give a complete answer. Feynman pointed out that when you ask why two magnets attract each other, there are different levels of understanding depending on your background knowledge. For someone with no knowledge of physics, the simple explanation would be the existence of a magnetic force causing the attraction. However, delving deeper into the question raises complexities that can be challenging to explain.

Feynman highlighted the difficulty of answering "why" questions in general. Explaining magnetic attraction in terms of something else that we are more familiar with, like rubber bands, would be misleading and circular, as it ultimately comes down to electrical and magnetic forces. He acknowledged that some aspects of the natural world may need to be accepted as fundamental elements without a more profound explanation.

This is echoed in the Vsauce video, where defining boundaries and attempting to explain everything can lead to paradoxes and vagueness. The concept of "boil-o" illustrates how composites, like chairs, can over-determine what happens in the world and our own perception, making their actual explanation even more elusive.