Voyager 1 Set to Reach One Light-Day from Earth on November 18

NASA’s Voyager 1 is expected to cross the <b>one light-day</b> milestone at 5:16 a.m. ET on Wednesday, November 18. The spacecraft is more than 16 billion miles from Earth, and a light-day is the distance light travels in 24 hours. Radio signals travel at the speed of light, so a message from Earth would take a full day to reach the probe. Voyager 1 left Earth in 1977 to explore the outer planets. NASA plans a celebration around the milestone, including a mission-team discussion the following day about the spacecraft’s journey and continued operation.