Voyager 1 spacecraft headed toward edge of Milky Way

December 14, 2010 12:00 AM

UPDATED December 14, 2010 12:05 AM

More Videos

  • What happens during a school lockdown?

    A school lockdown is a precautionary measure issued in response to a direct or nearby threat. It requires staff and students to respond quickly and comply with rules. Here’s how it often works.