Complex sentence: The minute hand of the Clock first moved closer to midnight in response to changing world events in 1949, following the first Soviet nuclear test, and is now set at two and a half minutes to midnight.
Split into simpler sentences: The minute hand of the Clock first moved closer to midnight in response to changing world events in 1949, following the first Soviet nuclear test. The Clock has been set forward and back over the years as circumstances have changed; it is now set at two and a half minutes to midnight.