Well, my father was in the Army and we traveled quite a bit when I was growing up, and I thought that I would like to have a military career, although I was drawn more towards the Navy.

What you aren't ready for being the first time in space - on an emotional and intellectual level - is how looking down at Earth will profoundly affect you. Over the long term, it has changed the way I think about planet Earth. When you go around the planet and look down, you think about the fact that this is the cradle of humanity, that this is a place where seven billion people, 200 countries, live side by side, that we share this place and there's nowhere else to go.

The most fun to do in the weightlessness is going down the ladder headfirst, walking on the ceiling, chasing after M&M's that you throw up into the air - they're just bouncing around all over the place and you go around like a fish eating them. I often tell kids that when you go into space and experience weightlessness, the serious adult in you gives way to the child you used to be, who had imagination, who had no bounds on what was possible.

In 1983, NASA invited Canada to fly three payload specialists, in part because we had contributed the robotic arm that is used on the shuttle.

I would love to see the world's space programs continue toward sending humans to an asteroid or to Mars, with, of course, a full plan in place to bring them back. That excites me. And one of the things that excites me most about space is that we can go up there and put spacecraft in orbit with sensors that will help us measure the health of our planet, which is becoming particularly important. Our planet needs to be observed.

I went to military college in Canada and graduated as an officer in the Navy but also as an engineer.

I wanted to further my education, so I went on to get a Ph.D. in electrical engineering and came back and served about ten years in the Canadian Navy as what we call a combat systems engineer.