It was the morning of Jan. 28, 1986, when the Space Shuttle Challenger launched from NASA’s Kennedy Space Center in Cape Canaveral, Florida — a moment that would soon become the nation’s worst tragedy in the history of space travel. It’s hard to believe that it’s been 40 years to the day since the Space Shuttle Challenger exploded just 73 seconds after liftoff, in front of the entire nation on live television. Millions of Americans, including schoolchildren, were watching because Christa McAuliffe, the teacher aboard the shuttle, was scheduled to teach a lesson from space. We were sent home for the rest of the day after witnessing what would become the nation’s most devastating space travel tragedy. Read More: New Details About Brett James’ Fatal Plane Crash: Aircraft Went Into a ‘Spiral’What Caused the Challenger to Explode?