In this video you see a pilot pouring water into a cup while the plane is doing loops. At one point the water seems to be flowing away from the Earth below him or remains in the glass even while the plane is inverted. What happened to gravity? Aren’t things like water supposed to “fall”?
Gravity thankfully is alive and well. What is happening is that the looping motion of the airplane generates a force directed towards the bottom of the plane. This force, called centrifugal force, is strong enough to counteract the force of gravity and make the water stay in the cup or even “fall up” (from the point of view of the camera) while the plane is upside down during the loop.
You can see my demonstration of this force in the video below.
My demonstration is not perfect in that to spin around the cup my arm has to produce a twisting motion that sloshes the soda around and generates foam, but the principle is the same. In the case of the video of the airplane, the motor propels the plane, and the navigation controls inside the cabin lock it into a circular path which generates the force. In the case of my video, the muscles in my arm propel the cup, and my grip on it locks it into a circular motion which generates the force.