Man's home is on land,but many thousand ago he leaned hoe two travel on the sea.
travel on sea was not a difficult problem. wood,which can be found in most places near the sea, floats easily on water.
but travel in the air was very difficult since man knewof nothing which could float in the air and at the same time carry a man's wieght. for a very long time man only dreamed of flying. in ancient greek times,there is story of two men who escaped from an island by sticking wings made of feathers