<p>The world-famous peace symbol, which turned 50 on April 4, 2008, was the brainchild of a British designer seeking a simple but powerful emblem for an anti-nuclear-weapons march in London in 1958. The symbol, which superimposes the semaphore signals for <i>N</i> (nuclear) and <i>D</i> (disarmament), caught on worldwide and quickly became a universal touchstone for the causes of peace and nonviolence.</p> <p>A new National Geographic book, <i>Peace: The Biography of a Symbol</i> by photographer Ken Kolsbun and journalist Michael S. Sweeney, takes a look at the famous pictogram.</p> <p>Here, a skywritten peace sign drifts above peace activist and folk singer Arlo Guthrie during a 1969 show at Tufts University in Medford, Massachusetts.</p>