The clock is currently the closest it has ever been, 90 seconds to midnight. But at 10 a.m. EST (3 p.m. GMT) on Tuesday (January 23), it could be set even closer to midnight. This means that the threat of global man-made catastrophe is closer than at any time since 1947, when the clock was designed. The Doomsday Clock is a symbolic timepiece that shows how close the world is to a global man-made catastrophe, experts believe. Every year, the clock is updated based on how close we are to the total destruction of humanity ("midnight"). If the clock goes forward and gets closer to midnight (compared to where it was set the previous year), it indicates that humanity has come close to self-destruction. However, if it moves back, further from midnight, it indicates that humanity has reduced the risk of global catastrophe in the past 12 months. (Jonathan Chadwick for Mailonline)