In order to fly:
- We need to overcome our own weight—that is, the force of gravity.
- To overcome gravity, we need to create an upward force called lift.
- To create lift, we need to generate thrust for forward motion.
- To keep moving, we need to overcome the resistance of the air—a force called drag.
But using only our muscles, we can’t get off the ground very high or very far for very long. So instead, we’ve created machines to do what we alone cannot. We separated the functions of lift and thrust, using wings to produce one and engines to produce the other.
Though we still cannot fly like birds, we can now fly with them.