Video-Underground nuclear tests
http:// youtu.be/7p_0Djq_-hY North Korea has vowed to carry out a third nuclear test, but scientists and concerned foreign governments may have a tough time verifying the actions of the reclusive state. After foreign detection of its 2006 test, Pyongyang carried out its 2009 explosion deep underground, which gave scientists far less information. Most observers expect North Korea to be even more careful this time.VIDEOGRAPIC