A nuclear test by North Korea will generate sound waves, seismic shock waves similar to an earthquake and, if the test site is not properly sealed, a spike in levels of radiation that will all be quickly detected by a global network of sensors, analysts say.
On June 30, Donald J. Trump became the first US president to set foot in North Korea. Trump made history when stepped across a low concrete marker accompanied by North Korean leader Kim Jong-un and walked a few steps into the North. The two leaders agreed to have their negotiators resume an effort to reach what has so far been an elusive nuclear deal. US President Donald J. Trump, accompanied by North Korean leader Kim Jong-un, stepped into North Korea at the border village of Panmunjom on June 30. Trump is the first sitting US president to set foot in North Korea. (Reuters/Kevin Lamarque)