Piers Sellers: Hello everybody! I'm ready for your questions.

Piers Sellers: Yes I have. When I was about 8 years old, I became aware of people going into space, and I was completely fascinated. I have been fascinated since then as well, but for many years I didn't think it would be a possibility, mainly because of my citizenship, and also because so many people want to do it, but so few get to go. So I carried on with science, which I loved. Getting selected to join the astronaut corps was marvelous, and a big surprise.

Piers Sellers: That's an easy one to answer--I studied the things I was really interested in, like biology and math and physics. And languages. From there, I went into a scientific degree track and a research career, and very nearly became a professional ecologist. But I got interested in computer simulation of the atmosphere, and how living things work with the atmosphere, so I kind of jumped sideways into the whole business of computer modeling. From there, NASA became interested in my work and invited me from England to do research here in the US. I spent about 13 years doing research on climate modeling, global warming, and things like that. But all the time, I was interested in becoming an astronaut, but didn't really think it would happen.

Piers Sellers: I think the main thing which people don't often think of is the sheer amount of study that has to be done. You have to really understand and know how to operate all these different systems on the shuttle and space station. The thing is on a spacecraft, the crews are very small--6 typically on the shuttle, and 3 on the station--so each person has to be able to do many different tasks, and that takes continuous study. By the time you've been through everything once, you've forgotten the earlier stuff and it's time to start again!

Piers Sellers: Not bad at all! But here's the surprising thing--if you look on the label and read what it says, you get an idea in your head about what it's going to taste like. This is the wrong approach! It's much better to just eat it and say, "That tastes good" rather than read first and say "That doesn't taste like what it says on the label," which it usually doesn't.

Piers Sellers: Some of the shuttle training, particularly the ascent training is pretty tough. Most of this is done in simulators, which are very realistic. They move, rattle and roll. During a simulated launch, the simulation team are always failing things on you, and in the middle of all the noise and confusion, you have to try to figure out very quickly what the right thing is.

Piers Sellers: We're not completely sure. Our best guess is that we'll have a warming of somewhere around one and a half degrees Centigrade over the next century. There is a large uncertainty in that. Now is the time for scientists who try to reduce that uncertainty, and for the public and governments to think about their next move.

Piers Sellers: We have satellites that can tell the difference between warm years and cold years, and wet years and dry years. What they see is changes in the patterns of vegetation greenness around the world, and these are much more varied year to year than most of us would think.

Piers Sellers: I haven't been yet. I'll go visit next year in August. The station will be used, hopefully, for studying all kinds of problems including some environmental ones. Right now, we're in the build phase, and the mission that I'll be on is taking up a big new piece for it.

Piers Sellers: When I go to the space station, it will be strictly as a construction dude, and not as a scientist. My friend David Wolf and I will go outside for 3 space walks, to install the new truss. This is a piece--a BIG piece--of hardware, that looks like a bridge. It will hold solar arrays which will provide power for the station. So really, on this flight, I'm a hard hat.

Piers Sellers: That's a good question. An enormous number of people have worked on this during the last 15 years, and we've had some real successes, I think. One thing is that we've found out that the biosphere is really helping out humanity. A lot of the CO2 that we put up into the atmosphere from burning fossil fuels gets pulled down by the earth's vegetation and stored. This actually delays or reduces the global warming effect, at least for now. What the biosphere will do in future with our fossil fuel emissions is a very important thing that we need to know. All my friends are continuing to work on this.

Piers Sellers: I think the biosphere, as a whole is pretty resilient. The main threat probably is the individual rare species because of human activity.

Piers Sellers: No, I haven't been yet. But I'm really looking forward to finding out!

Piers Sellers: The British only participate in some unmanned scientific missions. As yet, Britain does not contribute to the International Space Station.

Piers Sellers: Well, I think the whole crew is really focused on getting our particular job done. As soon as we arrive at the station, two days after launch, we'll be working flat out to get this truss installed and working. It'll be pretty much a work/sleep schedule until we get that done. The flight will run for about 11 days, and we're totally focused on getting this job done correctly.

Piers Sellers: My main job will be to go outside in a space suit with my friend Dave, and do three space walks. During this time, we'll make all the electrical connections and cooling connections between the new piece that we're installing on station, and the existing systems on station. We also have what looks like a little railroad car that can run up and down the length of station, and we get to try that out, which will be fun. All of this will be done while we're hanging on the outside of the station, moving at about 5 miles a second, 250 miles up. So the view should be good.

Piers Sellers: The research that we were involved with took us to all sorts of interesting places. For a while, we were looking at the effects of tropical deforestation on climate, and we worked in the Amazon basin in Brazil. I have some good friends still there in Brazil that I keep in touch with. Another project we had was to try and see how a climate and a vegetation on the edges of the Sahara affected each other, so we went to Niger to set up an experiment there. Probably the longest, biggest project that we worked out of our lab was an experiment that was looking at the possible effects of global warming in the great Northern forests. We spent many years working in northern Canada, trying to figure out how climate change would affect this place.

Piers Sellers: It's true that when we look at the history of the earth, we see cold periods and warm periods. But most of these happen for natural reasons that we understand, and over long time periods. For example, the Ice Ages we are pretty sure now were caused by wobbles in the earth's orbit around the sun. What we've seen over the last century is a very rapid warming, relative to these natural variations.

Piers Sellers: Well of course, I was overjoyed. I thought they might have made a mistake! It was a great feeling. And still is.

Piers Sellers: As an astronaut, I think our job is to make sure the whole team produces the desired results. There are thousands and thousands of people involved in the space program now, from all over the world, and it takes all of us working very hard and very carefully to achieve success. So, as an astronaut, we're just very visible, but still a small cog in this very large enterprise.

Piers Sellers: I think one of the best was when the research team gave me a joke present when I left science to go to Houston. I can't tell you what it was! But it was really kind. I think it showed that they'd miss me. And I certainly miss them.

Piers Sellers: I think the thing to do always is the thing that you love or are most interested in. Almost always, that will be the thing that you turn out to be best at. So I'd advise anybody to study and work at the thing that gives the most joy. And if the opportunity comes up to do something particularly interesting or fun, that's icing on the cake. Looking back, I would have been really happy to continue in science. We were working on important and interesting problems, and the company was the best in the world. While I was very pleased to become an astronaut, the scientific life would have worked out just fine as well.

Piers Sellers: I do enjoy this very much. I spent two and a half years going back and forth to Russia to help make the links between our program and the Russian space program. About 50 percent of my time over that two and a half years was spent in Russia. It was impossible to do the job without being able to speak the language--which turned out to be a lot of fun! While most of the formal negotiations take place in English or through interpreters, that's not how you get to know the people who you work with over the long haul. You have to be able to understand what they're thinking and saying in their own language.

Piers Sellers: I doubt it. NASA is a civilian agency, and nothing we do is secret. The military, I'm sure, has all the technology they need to do this sort of thing.

Piers Sellers: It's really turned into a completely international effort. The scientific community that works on this is relatively small, only a few thousand people. I would say about a third to a half of them are in the US, and the rest scattered throughout the world. The Europeans and the Canadians are particularly interested in pushing the science forward. and have had quite a number of successes. I think, as time goes on, you'll see more and more countries brought together to deal with this problem because it is a global problem that affects everybody. So everybody has an equal stake in getting the right answer.

Piers Sellers: In the astronaut business, most of the time, I've been working to try to bring different groups together to get particular problems solved. Very often, astronauts are used to try and persuade other groups within the space business to pool their resources to get the job done. The organizations involved are so big that quite often one part doesn't even know about the existence of another part. One of the most interesting jobs I got to do recently was with the Russian software group who were designing all the displays and commands for controlling the Russian part of the Space Station. This means the computer screens and things that astronauts and cosmonauts use to control the station. What we try to do, as far as possible, was to have the Russian and American and other partner displays all have the same look and feel to them. And it worked out. They're not all the same now--you can definitely tell a Russian flavor or Japanese accent on their displays-- but you won't be confused when you move from one set to another.

Piers Sellers: They work us pretty hard, as you'd imagine. I've always taken the precaution of living very close to my work, so I don't waste any time commuting. I have a four minute commute! I have two children and they (not me!) have a dog, so I have to say that some of my hobbies include clearing up after the kids and keeping the house from falling apart! The kids are 13 and 16, and they couldn't care less about Dad being an astronaut! Many of our friends are astronauts, so it's nothing particularly novel for them. As a family, we love to go visit the more beautiful parts of Texas, like the Big Bend National Park and the hill country. We go walking and tubing and eating Mexican food!

Piers Sellers: Not particularly. I'm encouraging them to do what they're really interested in. It looks like my daughter will end up being a doctor, and right now, my son wants to be a marine biologist. It's interesting that right now both of them seem to be motivated by the interest in a job, rather than earning lots of money. I think that's good. I've tried to impress on them that a job takes up at least half of your waking life, so you might as well enjoy it.

Piers Sellers: We can certainly see droughts and floods, and I think that's the most useful things in terms of observations that these satellites can give us. As yet, satellites can't tell us much about what goes on in smaller waterways or rivers.

Piers Sellers: Typically, we walk out to the shuttle about 3 hours before launch and strap in. Don't forget that during launch, the crew is lying on their backs with their knees and feet higher than their heads. The shuttle is standing on its tail, and the seats are arranged like they would be in an airplane-- they're arranged for landing. So when you put the shuttle on its tail, you're on your back. After three hours or so of lying on your back in a spacesuit, wearing a parachute and all sorts of other gear, comes the great moment. From there to MECO (which stands for Main Engine Cut Off) is only 8 1/2 minutes. So you go from lying on your back in Florida to coasting towards orbit in a very short time.

Piers Sellers: There's no hard limit. I think the most that any one person has done is six flights, but that record may be broken soon.

Piers Sellers: I think that there may never be a time again when there aren't humans in space. This period started with the first space station crew. I think it's highly possible that there will always be somebody off this planet from now on. As time goes on, I think we'll see more and more people from all walks of life experiencing space flight, and that's great.

Piers Sellers: I first flew gliders when I was 15. I got a pilot's license for regular airplanes when I was 17 in England. But Dad wouldn't let me drive his car until I was 21! I didn't have a car driving license until I was 22. So I spent many years freezing to death on motorcycles. I probably got over 1000 hours as pilot in command of aircraft, and maybe 1600 hours in total. I love flying

Piers Sellers: We did a lot of what we called "large scale field experiments." These were tricky. We had processes that we thought we understood on a very small scale, such as how plant leaves work to convert carbon dioxide and water into sugar (photosynthesis). It's one thing knowing how this works in a leaf; it's another to try and figure out numbers for the same process over the whole planet. So we did some experiments where we measured lots of things on the ground and with aircraft, while at the same time satellites flew overhead and took data. In the end, we were able to show that you could measure these things from space on very large scales. But in the process, we got bitten by almost every single mosquito in Canada, Israel, and Africa. Our typist is Canadian, and wanted to know which were the worst--without a doubt, the Canadian mosquitoes have the worst bite! But the fewest diseases. It's a tough choice.

Piers Sellers: Full-time, I'd have to say from 1982 to 1996. But I'm still thinking about it, so I guess it's a lifetime addiction.

Piers Sellers: Yes, people strap themselves into sleeping bags. Most people say they like to feel the pressure against some part of their body while they're asleep or trying to sleep. But to be honest, sleep seems to be a real problem in space. People don't generally sleep very well in space. We're not entirely sure why. Some people think that it's the day/night cycle being completely upset, like being jet lagged. The other thing is that the body isn't used to weightlessness and may find it hard to relax. People try to sleep against something firm to give the illusion of gravity.

Piers Sellers: People always are thinking of better ways to get from Earth to low-Earth orbit, which is by far the hardest and most dangerous part of space travel. It's also the most expensive. We have a number of ideas, but they're only in the planning phase. I'm hoping that somebody comes up with some good ideas over the next ten years or so.

Piers Sellers: I'm not sure. I guess I'll either be still working in the astronaut office with the space station or other projects, or I'd go back to science. It all depends on what NASA needs.

Piers Sellers: With my family? Sure. I think that would be great. Maybe 100 years from now, there will be families living in different parts of the solar system. I wonder when the first person to be born off Earth will be?

Piers Sellers: One of the most interesting things was that if we were to succeed in cutting down the entire Amazon forest, it would certainly change the climate of South America. And maybe have some effects on the global climate. That really was the main scientific result. Now, of course, (a) it's very unlikely that we'd cut down the whole forest. And (b) if we did, there would be greater losses to mankind than just changes in climate. But that was the problem that we set for ourselves and the answer we got.

Piers Sellers: Yes I do. Right now I'm not teaching at all, although I do give classes to new astronauts on the subject when they come in. But I like to teach. Students keep you on your toes!

Piers Sellers: It has changed everything! It's a truly marvelous new tool for getting information, staying in touch with people, discussing things. I really can't see how we did without it.

Piers Sellers: For all you students out there, study hard! And have fun. Thanks very much for all your questions. I had a great morning.