The clock is located on the wall of the Bulletin's office in the University of Chicago. The clock first measured the threat of global nuclear war. Something that was true alert when I was a young kid. Since 2007 it also keeps tract of climate change. January 2015 saw the clock move to 3 minutes before midnight and in 2016 the clock holds the same time.
The clock was introduced by the international group of researchers called the Chicago Atomic Scientists. Members had participated in the Manhattan Project. The group started sending out a newsletter following the atomic bombing of Hiroshima and Nagasaki. Later the group started sending out a bulletin. Since 1947 the clocks hands have bee reset twenty one times. The first setting of the clock was seven minutes til midnight.