The Millennium that Defined Earth

Explanation: When the second millennium began , people generally knew that the Earth was round , but few saw much of it beyond their local village. As the millennium progressed, humans mapped the continents , circumnavigated the globe , and determined the composition of the Earth . The Earth started as the center of everything , but became a planet placed in the Solar System , which became placed in a Galaxy , which became placed in the Local Group of Galaxies , which became placed in an expanse so vast we call it just the Universe . As millennium two ends people generally know what Earth looks like from afar , and how it is that all of humanity is confined to the surface of this fragile and watery globe .