The World Health Assembly officially declares smallpox eradicated, the first human infectious disease to be wiped out.
NASA launches Voyager 1 to study Jupiter and Saturn; it later becomes the first human-made object to reach interstellar space.
Vietnam becomes the 149th member state of the United Nations.
A team at the Pasteur Institute including Françoise Barré-Sinoussi and Luc Montagnier reports the virus later named HIV, the cause of AIDS.
ARPANET officially switches to the TCP/IP protocol suite, often regarded as the birth of the modern Internet.
NASA's Viking 1 lander touches down on Mars and returns the first images from the planet's surface.
Hundreds of thousands of people flee Vietnam by sea after 1975; many die at sea and others are resettled, mostly in Western countries.