Space is not just going up and coming back down again. Space is getting into orbit and being there, living there, establishing a presence, a permanence.

People communicate in Twittering ways. I've learned how to do that.

For a million dollars, the Russians would take two people, a million apiece, around the moon and back. However, stories, videos that come from the space station, and other people, are a great inspiration to young people for an exciting career field.

As time goes by, I'm increasingly impressed by how very special and timely it was that we got the degree of national commitment needed to put people on the Moon. For the first time, this nation was united in trying to develop an interplanetary capability. We've been trying to repeat that situation ever since.

I wrote 'Reaching for the Moon' because I wanted to tell kids that all of us have a moon, a dream, that we can strive for. Even if you don't attain it, you can at least reach for it.

I know: If you're looking down at Earth, you're looking through an atmosphere that has a bit of haze in many places and not just occasional clouds.

Mars has a bit of air pressure; maybe we can build up that atmosphere to be a bit more accommodating to humans.