Helicopter Theory Millions around the world watched

Millions around the world watched as the Apollo 11 astronauts "came in peace for all mankind" to take humanity's first steps on the moon

Greek Fairy Tales for My Children

The author traces the progression of new polyphonic forms from the Parisian motet of the 13th and 14th centuries through Italian song forms to the Franco-Flemish style of the 15th and 16th centuries

universal common

Helicopter Theory Millions around the world watchedThe history of the helicopter may be traced back to the Chinese flying top (c. 400 B. C.) and to the work of Leonardo da Vinci, who sketched designs for a vertical flight machine utilizing a screw type propeller. In the late nineteenth century, Thomas Edison experimented with helicopter models, realizing that no such machine would be able to fly until the development of a sufficiently lightweight engine. When the internal combustion gasoline engine