It’s been four decades since man first landed on the moon. Its significance is still not fully agreed upon today.

Andrew Chaikin is an advisor to NASA and the author of “A Man On The Moon,” the book upon which Tom Hanks’ Emmy winning mini-series “From The Earth To The Moon” was based.

For his latest book, “Voices From the Moon,” he visited with each of the men who set foot on lunar soil to find out how the experience changed them. Some came home profoundly different; others, not so much.

His discussion sheds light on how difficult a task a trip to the moon really is, and how it changes human perspective.

Want to learn more about space pioneers? Click here to meet Col. Joe Kittinger, the first man to get to space.