Airplanes

"It made the world "shrink" because people can not travel to and across places which

are previously inaccessible (e.g. airplanes can fly over mountains). Airplanes have also

significantly reduced the time needed to travel from one country/continent to another.

However, it also affected humans negatively because problems such as air and noise

pollution soon appeared."(http://wiki.answers.com/Q/How_did_airplanes_affect_humans)