cold war 1945 - present By averemm 1961 Berlin wall https://docs.google.com/document/d/13Xc8J1eCf3rnWCAp-1BI_1SBD6tIMhuzp6sD1UZ2JCU/edit?usp=sharing 1986 challenger and columbia https://docs.google.com/document/d/1oqSydwSb_zLFZpCutb-gcwvPtzGTeRBk0V0ZgzaiVuc/edit?usp=sharing
