Hi guys, I've heard that this topic has been discussed to death before but hopefully not here yet I apologise if it has been. I'm currently in high school we're just into bernoulli's equation and one of the applications is the airfoil. Our textbooks states that the fundamental source of lift is the difference in velocity of airflow over and under the wing hence the difference in pressures which will in return create lift. However it also states that as the airfoil flies through the air, for the velocity of air over the airfoil to be faster than the underside, the air that is separated at the leading edge must converge at the trailing edge. How true is this? If it is, can anyone offer an explanation beyond just the shape of the airfoil on why this will happen? I've done a bit of research on the internet and some sites states that this is not true, that wind tunnel tests have shown otherwise and that Newtonian physics is involved - the wing diverts air downwards and gains momentum. How is it possible for a wing to divert so much air downwards (it's not even close to vertically downwards I think?) to support the weight of say a B747. Which is the main principle of lift?