金沙官网网址大全

Taking flight

作者:东方丑厣    发布时间:2019-02-27 02:11:01    

By Paul Marks A GLANCE up at a low-flying Boeing 747 jumbo jet invites the question: how can anything so vast support itself in mid-air? Just what is it that keeps these 300-tonne aluminium monsters in the sky? It’s the same thing that keeps the tiniest bird or insect aloft: a phenomenon called lift that is created by the motion of the air over some specially shaped surfaces. Birds,

 

Copyright © 网站地图