The Safeguard Complex
It opened on October 1, 1975, and closed on October 2, 1975. Of course, this led to conspiracy theories. Some say the building is actually used by the Illuminati, the biggest "secret society" in existence.
Extraterrestrial Signal
On August 15, 1977, astronomer Jerry Ehman recorded a radio signal using the Big Ear telescope at Ohio State University. The sound that he heard was so loud that he quite literally wrote down, "Wow!" on the printout. The sound lasted for 72 seconds.