Its power had to come just from a toss of the hand, without aid from a slingshot or some other help. So NASA showed them where to place the wings on the glider, plus the right angle for the tail surfaces, and how to shape the foam to fly smoothly in the air. The weight of our body depends on how hard gravity pulls on us. Some of the other planets in our Solar System are bigger than Earth, and some are smaller. How much you would weigh on a planet depends on the planet's size.
Gravity is a force everywhere, but sometimes scientists want to do studies without gravity's pull.
We can make things weightless for a short time by dropping them a tall tower. We can make them weightless for longer times in a spacecraft orbiting around the Earth. They can see what happens when gravity is absent from a process, such as the growth of animal or plant cells.