Who discovered the ancient Inca city of Machu Picchu?.

How did german physicist werner heisenberg's uncertainty principle shake beliefs in newtonian physics?

Why do people place so much importance on washington, dc?me

Which statement about submarine use in world war i is true? the allies never found a way to counter german submarine warfare. germany’s use of submarines affected the united states’ decision to enter the war. only the germans used submarines in world war i.