Have you ever wondered why falling objects fall downward? What keeps them from shooting up into the sky? There is one force that's so strong that everyone and everything on our planet is being pulled to the ground by it all the time. The force is called gravity. It cannot be seen or felt but it is always around us. Only certain objects, such as airplanes and hot air balloons, can defy gravity for a time but, in the end, they always come back down to Earth.