John Cromwell Mather

I think people have a really hard time grasping how empty outer space is, in the sense of immense distances between objects, and immense time spent going from one to another. There's a lot of talk about space aliens as though it were physically possible for them to get here from somewhere else, and (sorry to say this) talk about human travel out of the solar system. We just don't live long enough to do that.

1) JWST has no liquid gases for cooling. Our early design had solid hydrogen instead, but we've replace that with a closed-cycle refrigerator using helium gas sealed into the equipment. So, fuel for station-keeping is the limiting factor. By the way we also use the fuel for countering the built-up torque due to solar photon pressure on the sunshield.

2) JWST will orbit around L2 like WMAP. WMAP has been sent off into interplanetary space, so it's orbiting the Sun after a very gentle push-off.

3) JWST arrives around L2 in 2 months, which is about the same time it takes to cool down to operating temperature. We are expecting to be in routine science observing mode 6 months after launch

Dark energy is probably the hardest thing to study. We have no prediction that it can ever be observed in the laboratory, and the things we have in mind to do in astronomy can only reveal the history of the accelerating expansion, not the reason for it.

But, forever is a long time! I think this just means that theoretical physicists have many ideas and some may work out.

1) Good question! The James Webb Space Telescope is the next big thing in astrophysics, and the Decadal survey produced by the National Academy of Sciences says the next thing after that should be the WFIRST, an wide field infrared survey telescope. Now that the NRO has donated 2 sets of optics to NASA, perhaps one set will become WFIRST. We also have in mind plans for the next great Xray observatory, and a search for gravitational waves using a space interferometer. I think we have at least a century of amazing ideas to carry out.

2) Best thing about working for NASA: thinking about such wonderful possibilities and seeing ideas become reality. Also, I love working with teams of brilliant scientists and engineers every day. Each day is different, and I am so proud of what we are doing together.

I think we will be swimming in oceans of pictures and data and new discoveries from JWST and other new equipment. Our ground-based telescopes will be about 3x larger than they are today and some of them may have the capability to directly image exoplanets using extreme adaptive optics.

Looking at the stars was the beginning of quantitative science, and still propels new advances in technology as well as fundamental discoveries about our history and our place in the universe. People want to know how we got here, are we alone, and where we are going. Astronomy answers part of that.

I think JWST can produce stunning surprises in many areas. We don't know how galaxies formed or when, we don't know how they got supermassive black holes in their centers, we don't know whether the black holes caused the galaxies to form or vice versa. We can't see inside dust clouds where stars and planets are being born nearby, but JWST will be able to do just that. We don't know how many planetary systems might be hospitable to life, but JWST could tell whether some Earth-like planets have enough water to have oceans. We don't know much about dark matter or dark energy, but we are expecting to learn more about where the dark matter is now, and we hope to learn the history of the acceleration of the universe that we attribute to dark energy. And then, there are the surprises we can't imagine!

Great! No, I never regretted my choice to study physics. But today, something else might be fascinating too. Every day I read of breakthroughs in biology and technology that are breathtaking in their implications. For instance, people are designing a transistor that has only ONE atom! Then, there's artificial intelligence, which has been harder than people thought, but is making progress.

Nope, I've never been unemployed. But it's always good to be alert to other opportunities.

I think history. I know just enough to see the tremendous rate of progress since Archimedes, and I'm eager to see what the next discovery is every day. I also think a bit about human organizations, since science is such a social enterprise. If you read Darwin's Origin of Species, a lot of the text is about thanking people for helping him get information. So scientists have been social since the beginning.

1. It was the one with the greatest unsolved problems! When i was a student, we didn't know much about the elementary particles, but we had a chance to learn so much. Then, it turned out I had a good mind for physics and math, and it was a lot of fun learning how to think about the mysteries, like relativity and quantum mechanics.

2. The Nobel work came by a roundabout path. My thesis project at Berkeley was chosen because it was exciting and I liked the professors. Then it failed to function and I thought I would give up on the cosmic microwave background radiation. Then, I was a postdoc doing radio astronomy and NASA asked for satellite proposals; that was 1974. i said, my thesis project failed, but it should have been done in outer space. So we wrote a proposal and it was chosen.

3. About the Nobel, a lot of people thought the COBE was Nobel-quality work, but I thought, the competition is fierce, and only people like Einstein get on the list. So it was a lovely surprise!