Without the atmosphere there would be no weather , no wind , rain , snow , or clouds . Air is all around us ; we live at the bottom of a great ocean of air . It is invisible , but we can feel it when it moves . There are miles of air above us , pressing down with great weight on the earth and everything on it . Because air presses down on us from all directions at the same time , and because we are able to bear（忍受）this weight , we do not seem to feel it . But scientists have proved that air has this weight , and that anything that has weight creates （产生）a force called pressure . As changes in air pressure take place , they make air move .
