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a chance to make a trip into space with my friend Li Yanping, an astronomer. We visited the moon in our spaceship! Before we leave, Li Yanping explained to me that the forece of the gravity would change three times on our journey and that the first change would be the most powerful. Th en we were off. As the rocket rose into the air, we were pushed back into our seats because w e were tr ying to escape the pull of the earth gravity. It was so hard that we could not say anything to each other. Grad ually the weight lessened and I was able to talk to him. Why is the spaceship not falling back to the earth? On the earth if I fall from a tree I will fall to ground. I asked. We are too far from the earth now to feel its pull, h e explained, so w e feel as if there is no gravity at all. When we get closer to the moon, we shall feel its gravity pulling us, but it will not be as strong a pull as the earths. I cheer ed up immediately and floatedweightlessly around in our spaceship cabin watching the earth become smaller and the moon larger. When we got there, I wanted to explore immediately. Come on, I said. If you are right, my mass will be less than on the earth because the moon is smaller and I will be able to move more freely. I might ev en grow taller if I stay here long enough. I shall certainly weigh less! I laughed and climbed down the steps from the spaceship. But when I tried to step forward, I found I was carried twice as far as on the earth and fell over. Oh dear, I cried, walking does need a bit of practice now that gravity has changed. After a while I got the hang of it and we began to enjoy ourselves. Leaving the moon gravity w...