What 4 technological advancements made European exploration possible?

What other notable achievements must European society have reached even to make this exchange of letters possible? Which statements best describe how the Transcontinental Railroad helped lead to the closing of the western frontiers? What is the origin of the word civilisation? What were the major problems of keeping such a large empire running smoothly? What did the English learn from the Muslims and crusades? What is meant by the term porous frontiers? How many people died in the fourth crusade? What are some uses for trajan's forum? What were public squares in roman cities where people could gather to listen to sheeches called? What city was the westernmost extent of the Persian Empire? On the wagon history? What did the Chinese face while they were moving west? What was Calicut nicknamed in the Middle Ages What types of goods were traded in Calicut's port Where is Calicut located How did medieval travelers describe Calicut What is Calicut's climate? What was the British bastion in the west? What modern day country is Byzantium located? What happened in 1099 with the crusaders? When did spartacus become a gladiator? What phrases came to define the idea that whites should help civilize nonwhites? In which millennium was the year 1935? How did the Crusades lead to the Renaissance?