December 1973Monday 03: Pioneer program: Pioneer 10 sends back the first close-up images of Jupiter.
Tuesday 18: The Soyuz 13 was launched.
Sunday 23: A Sobelair Caravelle passenger jet crashes in Morocco, killing 106
Tuesday 25: The ARPANET crashes when a programming bug causes all ARPANET traffic to be routed through the server at Harvard University, causing the server to freeze.
Friday 28: Alexander Solzhenitsyn publishes Gulag Archipelago
Sunday 30: David Wilson and Bunny Clinard are wed at Bethesda Baptist Church in Macon, GA
I'm saying that last one had the greatest effect on all mankind. :)