This is a science lesson. So if you have no interest in science, stop reading now.
You know the saying, “You cannot keep an old dog from teaching old tricks.” I taught science for 37 years, so I cannot help thinking about scientific principles while gardening. For instance, every time I use my leaf blower to move a stubborn magnolia leaf that my neighbor’s tree has provided, I think about Bernoulli’s Principle. Good old Bernoulli discovered that the faster a fluid moves, the lower the internal pressure. The next time you fly (in an airplane) look at the wing. You will see that the upper surface is curved compare to the bottom surface. This causes the air moving over the top of the wing to travel a longer distance than air beneath it. The air on top therefore has to move faster to get the back of the wing at the same time as the air beneath it. Since the pressure on top is reduced, the greater pressure beneath will lift the wing (and hopefully you along with it).
So why, when I blow air over the top of a magnolia leaf, doesn’t it rise? Well, unfortunately I know the answer. Technically it is called “angle of attack”. (LaVille and I used to fly small planes.) The air blown at the leaf is coming down on it rather than parallel to it. I supposed if I laid the blower down on the ground so that the air flowed along it, the leaf might rise. But that would look stupid, and I get ridiculed enough as it is.
So the next time you are out blowing leaves and a leaf sticks to the ground so you have to go and kick it, yell out “Where’s Bernoulli?” . . Or the next time you are flying along in a plane, say a silent (or loud) thanks to Bernouli. He’s doing a great job of keeping you up.
Stan, The Science Man