What prevented the Europeans from exploring early?

How could the roman empire have prevented its fall in the west? What is the spiked club of Middle Ages? What was the style of Roman portrait sculpture? How were the Romans towns designed? What were the short and long term effects of Indian removal to the West? When was the pocket watch invented? Would the west have risen( to dominate the globe) as it did in the later half of the millennium if not for southernization? How long ago was the beginning of 12th century? Who killed mark Antony and conquered Egypt? What is Patrician definition? Who invented the cowbell? When was Habyarimana killed? What is past continuous tense? What was re-birthed during the renaissance period? When was the first vasectomy? Why did travel around the countryside increase by the 11th century? What century was 1275? What roman princples of government were incorporated into the US constitutions? Did Samuel de Champlain find a North West passage to Asia? What does englih share with latin?