James Peebles Interview: Conversations with History; Institute of International Studies, UC Berkeley

A Cosmologist’s Intellectual Journey: Conversations with James E. Peebles, Professor Emeritus of Cosmology, Princeton University; October 12, 2006 by Harry Kreisler

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Looking to the Future

Where do you see the most exciting problems down the road for this field, and what body of theories, which would then have to be confirmed, will be most instrumental in pointing the way?

It's always controversial. Different people have very different opinions. Some will say cosmology is getting dull, we've answered the main questions, but I don't understand why they say that. Well, perhaps I do. We have answered some big questions: Is dark energy really there? Yes. Is dark matter there? Yes. But what are these things? And so, we have right in our face, up close, big, open questions. Will we be able to answer them? Time only will tell.

Of course, there are other directions to go, and they are not necessarily along the directions we've been following. For example -- we think we're so smart, we understand galaxies. We don't understand our own galaxy! Astronomers are starting to turn back. There was somewhat of an imbalance in astronomy in the past decade or so that the astronomy of the nearby universe was neglected in favor of the glamour of looking out to the edge of the universe. There are definitely fads. They operate in clothing styles and they operate in science. The cosmology of the nearby universe, the science of the universe as studied by nearby objects, was neglected. In particular, our galaxy has been neglected. Shameful. We live here, we ought to look into it a little. It has lots of fascinating properties that will teach us about how it formed -- is teaching us about how it's formed. These lessons are just being taught to us now.

So, very clearly, in the next ten years there's going to be a lot more work on nearby galaxies, studying in detail their properties and teasing out hints to how they formed, which of course is what we attempt to understand when we look at distant galaxies seen in the past as they were forming. Clearly that's going to be a big activity. Finding nearby planetary systems -- fascinating! Finding out if any of those planetary systems contain terrestrial planets -- wow! Is there oxygen on any of them? How could you resist looking?

Styles change because, in part, technology solves one set of problems, opens up others; or maybe they're so difficult that you would turn instead to areas you've neglected. One thing about astronomy, we're in no danger of running out of things to look at. It's a big universe.

What about bodies of theory that might be brought to bear on problems in other areas of physical science?

I am particularly taken with the puzzle of the body of theory of the dark sector, so called dark matter, dark energy. We pause to consider that in our sector, you and I and the things we can see readily that interact with light, we have a set of laws of physics that are wonderfully simple. They're not all that simple but you can write down the basic laws of physics on a couple of sheets of paper. Its expression is spectacularly complicated. As far as we know, you operate according to the laws of physics, at least to a good approximation to the known laws of physics. You are a spectacularly complex expression of a simple set of laws.

In the dark sector, the laws of physics as we now postulate them are so amazingly simple that their expression is simple. They're dull. The dark matter piles up into what we call massive halos, the stuff that envelopes each galaxy. The dark energy just sits there, doesn't do much of anything at all. Is that really the way it is, or is it the simplest, most ridiculously idealistic approximation we could get away with at our present level of knowledge? I emotionally reject that. It's strictly emotional. I say, I bet you there's a whole body of physics to be discovered that will describe the behavior of this dark sector. Call again in twenty-five years and see whether I was right!

I'm interested in that "emotionally." Let's clarify that. It's a hunch based upon where you've been, what you've seen, what you've thought. Help me understand that.

Well, let's face it, I'm asking myself, "Have I worked myself out of a job? Has the science of cosmology come to an end?" By emotional, I really meant, oh my goodness, fear -- but perhaps over-exaggerated. Emotion, yeah -- I want the universe to be more complicated than it is, more interesting. That's an emotion, it's a hope, a longing.

It's an explanation of what drives that emotion. And it makes sense.

I hope so.

Isn't that key to the enterprise?

I hope so.

One final question. If students are grabbed by the discussion of your career and of these sets of problems, how would you urge them to prepare for their future in this field, build the groundwork, so to speak?

I have no idea. I have no idea. Work hard, do your homework, but keep interested in the world around you.

And it sounds like, "build things" too, in your particular field.

Yes, yes. Of course, each scientist is different. Some people build things a lot, others don't. Others have never touched a hammer. No, there're no universal rules that I know of aside from do your homework but don't get locked up in your homework. I guess that's the real trick, isn't it? Because when we teach students in university we set them exams in which the problems are totally artificial, because these are problems that have solutions. Nothing you do in research has a non-solution. If it had a non-solution you wouldn't be doing it. So, we teach these students the wrong thing. It often puzzles me: Why are we doing it that way? The only answer I know is, we don't know a better way. But the real trick for a developing scientist, I believe, is not to get locked into being totally adept at answering already solved problems. Treat them as what they are meant to be, practice. Keep your mind ready to address the unknown.

On that note, Jim, I want to thank you for taking the time to have this conversation and share your intellectual odyssey with us.

It has been a pleasure.

And thank you very much for joining us for this Conversation with History.

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