North Korea has threatened the United States with a preemptive nuclear attack. The threat came hours before the United Nations Security Council approved tougher sanctions against the regime. North Korea is not believed to have the capability the launch such a strike. Sally Kidd is in Washington with the latest.
SpaceX's Dragon spaceship splashed down Saturday in the Pacific Ocean, returning from a four-week resupply mission to the International Space Station and bringing back a valuable payload of potentially groundbreaking experiments.