The Navy's paid for you to go through school, and then they need doctors to go out and take care of people who are in various different parts of the world. I decided to pay back my time first as an undersea medical officer. I was stationed in Scotland.

I can't think of anything specific growing up that pointed me toward NASA at all. I was interested in the Moon landings just about the same as everyone else of my generation. But I never really thought about being an astronaut or working in space myself.

The microgravity or the very, very low amount of gravity that we have up in space forces some changes in different processes. It forces changes in us as human beings.

Everyone that I've talked to who's been to space has thoroughly enjoyed the experience, and what you often hear them say is: It was great, but we just had to come home.

We've had such thorough training, we've had an excellent team on the ground. With the minor glitches that have occurred, we've been able to take care of them. And the teams on the ground are getting tons of incredible data.

Gravity pulls our bodily fluids down, like water in a glass goes to the bottom part of a glass. In space, the water doesn't stay in the bottom of the glass. It distributes itself evenly over time throughout the entire volume of the glass.

Some things are only capable of being done in space. Examples of that are looking at our Earth from that far away, and understanding the entire processes of storms and weather patterns, and oceans, and coastlines.