[reading time 5 minutes]
How Airplanes Do Not Fly
Have you heard that airplanes fly because of the Bernoulli Effect? This is as far from true as the sun travels around a fixed earth. Stay with me, we need to peel off this bandaid as soon as possible, that new flesh may grow underneath.
The Bernoulli Effect gives us a way of understanding a small part of the universe and it is very useful - useful when you want to design a slow airplane. But you did not come here to know how to make an airplane fly, we seek to know how it is they do fly. In that case, the Bernoulli Effect is the opposite of useful - it is misleading.
The Bernoulli Effect tells us that given a flowing fluid (e.g. air), certain shapes (e.g. wings) may interact with said air such that local velocity increases and local pressure decreases. Further, using Newton’s Laws, this pressure drop can be seen as a force which may oppose the force of gravity, the latter otherwise keeping the aircraft on the ground.
Let us take this seriously for a moment. What does this say about the universe in which we live? It allows us to believe air and other fluids are special substances which provide for us the magic of flight. Furthermore, if air is the hero of this story, the antagonist is gravity, which through Bernoulli and Newton is made to seem mighty and can only be overcome with great effort.
The truth is, gravity is extremely weak and is overcome constantly and readily in our daily lives. And yes, air can be made to overwhelm gravity acting on an airplane but it does this no differently than the ground upon which you walk keeps you from falling toward the center of the Earth.
How One Walks Upon the Earth
Could there be anything more ordinary than going for an easy stroll? Or consider, even, simply standing in place. The truth of the events behind such moments - if pondered properly - is of immense importance. Here we will see, while the frontiers of science play out in the deepest stretches of the cosmos as black holes collide and send spacetime waves to our shores, and particle accelerators expose quarks to oblivion, these very same extraordinary events play out right here beneath our feet.
We know from our best physics that our local spacetime is curved straight toward the center of our massive Earth. Have you ever seen this warped spacetime? Drop a pen and watch it fall to the ground - there, you have seen spacetime. The pen’s path (in the absence of other events such as wind) exactly tracks the local curvature of spacetime. Before general relativity, this spacetime curvature was known as the force of gravity. But general relativity gives us a newer and better understanding of our universe, not just in the deepest reaches of the cosmos, but also here in our backyards. We must learn to live with this newer and better understanding - take it seriously in all questions of physics - before we can ever hope to move beyond this model. This includes a consideration of how airplanes fly. And how we walk upon the Earth.
Stand in place, wherever you are, right now. Feel the weight of your body pressing through your legs and feet. Feel the Earth pressing back. What you are experiencing is in point of fact millions of electromagnetic events holding the material of your body together, keeping that material from passing through the material of the Earth, as the curvature of spacetime drops you like a bucket down a well. That is the feeling of overcoming gravity, which is most easily accomplished by your body since we know from physics that electromagnetic interactions are much much stronger than our interactions with local spacetime. Indeed, this is how you can move your arms and legs with impunity. Ballet is flight on Earth; flight, ballet in air.
What does it feel like to fly on a commercial airplane? It mostly feels like sitting in a chair on the ground. Only the aircraft is unstable, dropping and lifting and tilting often. But these are the same feelings you would get if the Earth were unstable, for example, if you were in an earthquake. When the Earth drops from beneath you in an earthquake, do we say you are flying? No, we say you were in an earthquake.
Air is material, just as Earth is material. Only there are relatively fewer particles to interact with in air than in Earth. We may easily displace it. But the same exact interactions occur whether we push air or push Earth.
How Airplanes Fly
An aircraft simply employs velocity to make electromagnetic interactions with air more like those our feet are familiar with on the ground. And there it is. Why is this a much better explanation than Bernoulli? Because it is much closer to the reality of our universe. It is less immediately useful to our small intellects which satisfy themselves with an engineering understanding of the world. But as we’ve seen, this utilitarian point of view is at odds with true reality. We must live with truer descriptions of everyday events - take quantum and cosmological physics seriously - in order to take the next leaps in understanding what is truly there.
So go. Let your footsteps be as prayers upon the Earth. Be thoughtful and enjoy the magic of everyday events. Consider the electromagnetic air upon your face. Let your limbs dance with spacetime. Fly, as airplanes do, through your days and nights.