| They allow him unusual balance, enabling him to overcome gravity and stay upright when he should be prone. |
| In fact, scientists could and did show that gravity was too weak a force to account for the movement of continents. |
| For that to be possible, gravity and acceleration must be exactly equivalent to one another. |
| Attached to a single center of gravity by a harness made of strong webbing, hang gliders fly with bodies vertical. |
| But even after nearly 90 years the theory remains notoriously hard to test because gravity is such a weak force. |
| The interaction of the acceleration of gravity on the mass of our body produces the force which is called weight. |
