How People Learned to Fly

How People Learned to Fly

人类是如何学会飞行的

When you see a bird flying, do you dream about flying too?

当你看到一只鸟在飞翔时，你也会梦到飞翔吗?

Do you run with your arms out, imagining that you're soaring among the clouds? Do you make paper airplanes? Do you fly kites? If you do, you aren't alone. For thousands of years, people have dreamed of being able to fly.

你是否张开双臂奔跑，想象自己在云端翱翔?你做纸飞机吗?你放风筝吗? 如果你这样做，你并不孤单。几千年来，人们一直梦想着能够飞翔。

They watched birds and bats soar. They imagined people and other animals that could fly and told stories about them.

他们看着鸟儿和蝙蝠翱翔。 他们想象会飞的人和其他动物，并讲述他们的故事。

They designed machines that they thought would be able to fly. They had many ideas. As they tried each new idea, they learned a lot.

他们设计了他们认为会飞的机器。 他们有很多想法。当他们尝试每一个新想法时，他们学到了很多。

They learned about gravity. Gravity is the force that keeps everything on Earth's surface. Because of gravity, things have weight. If there were no gravity, people, dogs, cats, and everything else would go floating off into space. Gravity keeps us on the ground, even if we would rather be flying.

他们了解了重力。重力是使地球表面的一切保持不变的力量。因为重力，物体有重量。 如果没有重力，人、狗、猫和其他所有东西都会飘向太空。重力使我们留在地面上，即使我们宁愿飞起来。