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Across the universe

Astrophysicist Adam Frank brings the cosmos back down to earth

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Part one of a two-part series.

Dark matter, dark energy, and the Big Bang are ideas so large and seemingly intangible it's not easy to get a grip on them. Adam Frank, associate professor of physics and astronomy, theoretical astrophysics, and plasma physics at the University of Rochester, wrestles with concepts like these every day. Despite the complicated nature of his work, he manages to describe it in compelling and understandable prose in articles for Discover and Astronomy magazines.

            Frank, who lives in Rochester with his wife, Holly Merrill, and his two children, Sadie and Harrison, has managed to retain the sense of excitement, awe, and wonder that he had as a child, when his father took him to the Hayden Planetarium in Manhattan. In fact, he could have told you then what he'd be doing today.

            "I never really had any choice," Frank says. "The earliest memory I have is when I was 5 years old. My dad had a big library and he had amazing science fiction magazines --- Isaac Asimov, etc. --- and they always had cover paintings on them of guys bouncing around on Jupiter or something. Those were so cool."

            We recently sat down with Frank to try to get an understanding of the latest breakthroughs in astrophysics. Along the way our conversation touched upon art, philosophy, and the theory of everything. The following is an edited version of our interview.

City:We're here at a big university, in a fairly large city, on a big continent, on a huge planet, in what seems like an enormous solar system. You take it from there.

            Frank: It's hard to explain how small we really are. Nothing in our day-to-day activities gives us a sense of the vastness or emptiness of space. We are orbiting around a small star; there are nine planets that we know of. The solar system, by our scale, is quite large. We sent the Voyager probes out in 1977. They've been traveling 25 years; they've just now gotten to the edge of the solar system. But our solar system is barely our backyard. The distance to the nearest star is probably about 10,000 times farther than the distance to the edge of the solar system. That's our next-door neighbor. The Milky Way galaxy, our local city of stars, has a hundred-billion stars and is about 100 million times larger than the size of the solar system.

            City:And there are many more galaxies.

            Frank: Yes, virtually uncountable galaxies. When we look in the sky we see hundreds of millions of galaxies, each one with hundreds of millions of stars.      City:Humans have been looking at the sky for millennia and seeing heavens or constellations created by connecting the dots. Give me a brief history of our perception of the stars.

            Frank: A thousand years ago we thought there were five planets; we didn't know about Uranus, Neptune, and Pluto. Then we thought the stars were on a bowl or a sphere out at some distance not too far. It wasn't until telescopes got better in the 1800s that we really got a sense of how big the universe was. Even 100 years ago, we weren't sure there were other galaxies.

            It was just 500 years ago that the Polish astronomer Copernicus showed us that the earth was not the center of the solar system. That was a huge conceptual shift displacing us from being at the center of the universe. Suddenly it was the earth going around the sun. And of course it must follow that the earth must not be very important, because all the planets go around the sun.

            Later we realized that the sun wasn't at the center of the universe, but just one star in these uncountable numbers of stars in the galaxy. Then we learned that the galaxy wasn't the center of the universe, but just one of an unmeasurable number of galaxies. Part of our education as a species over the last 100 years has been our understanding that we're nothing special, at least in terms of location in the universe.

City:What's the latest theory on the composition of the universe?

            Frank: Recently, something very funky has happened. Over the last 50 years we've come to understand that when we look out at the night sky and see all those bright shiny lights, and when we look through telescopes and see distant glowing galaxies, we're only seeing a small fraction of the stuff that's out there.

            There has been a discovery of what is called dark matter --- matter that we can't see directly, but we can see its influence through gravity. We see galaxies spinning and we can measure how fast they're spinning. There's a direct relation between how fast they're rotating and how much mass is in them. What we find is that they're spinning way too fast for the amount of glowing stuff, so it has to be that there's a huge amount of stuff around the galaxy that is invisible to us.

            City:I've read that what we see or know of is only about 27 percent visible matter and the rest is dark matter or dark energy.

            Frank: It's actually worse than that. Luminous matter, the kind of matter that we're made out of --- our hands, computers, books, everything we can even imagine touching --- makes up only about five percent of the universe. The majority of matter is dark matter. Now we have also discovered a kind of dark energy too, through observations of stars exploding in very distant galaxies.

            City:The Hubble Space Telescope acts as a time machine, because of the time it takes for the light to reach us.

            Frank: Yes, the farther out you look in space, the farther back you're looking in time. We're now able to see back very close to when the universe was born with the Big Bang. We thought it was like an explosion: things get flung out and they're coasting. Now we realize they're not coasting, they're accelerating. There was the Big Bang and then some kind of energy pushing things farther and farther away from each other.

So it's taking this Copernican idea and pushing it to the limit. Notonly is the universe vast and we're not significant because it's so big and we're just a little tiny planet going around a little tiny star, but actually our kind of matter is not even the important part if you add it up. We're kind of an afterthought. It's like there's this amazing landscape and all the things we can see are just the Christmas lights strung on top of the landscape.

            City:And yet, look at the complexity of each of us. Leonardo da Vinci believed the human body was a microcosm of the earth in terms of the way liquid nurtures an intricate system. Now that we know about the multiplication of cells, brain waves, etc., could a case be made that the human body is more of a microcosm of the cosmos?

            Frank: We're so incredibly complex; we're sort of everything and nothing at the same time. We are insignificant in a tiny part of the universe that is insignificant, but, on the other hand, what we think we understand about dark matter is that it doesn't clump. You can't get a dark planet or a dark tree. The most complex structures you can form are big fluffy halos that stretch across tens of thousands of light-years. You can never get it to coalesce into anything like a rock.

            So most of the stuff in the universe, the dark matter and dark energy, will never form structures like planets. But our kind of matter can form this amazing complexity through the organization of biological molecules. With our kind of matter you can get this enormous capacity for organization --- trees and birds and life, essentially. So we may be incredibly significant.

City:Is the earth and all of its life simply a fluke?

            Frank: There are a couple of different frontiers in astronomy right now. One is cosmology; we actually have the ability now to gain quite a bit of understanding about how the universe was born, and that includes dark matter because we can see its influence.

            The other frontier is star and planet formation. In 1996, for the first time, we had really clear evidence that a star much like the sun had other planets going around it. That was a revolution. That question has been around for at least 3,000 years. Giordano Bruno, a famous heretic around the time of Galileo, was burned at the stake because, among other things, he believed there were other planets orbiting stars; the earth was not unique.

            City:The Pope recently declared that Galileo was not a heretic.

            Frank: [laughs] Yes, it took a little while but they finally got around to it. Astronomy can be very contentious, very dangerous. This idea of other planets, or the "many worlds" hypothesis, has been around a long time. It's amazing that in our lifetime we have seen this question answered. Since 1996 we have been discovering, indirectly, planets going around other stars. We can see the star wobble back and forth as the planet goes around it.

            City:How much closer does this get us to finding life out there?

            Frank: This discovery is huge; it takes the first step because you're going to need a planet to have life form. We have now found about 100 stars that have planets orbiting them. That means we can start to do a census of these planets. Looking at our solar system, it looks like life only formed on earth. It may have formed on Mars; Mars at least had the right conditions. But there are "habitable zones" around a star, a region where liquid water can exist. So there's only a range of places you can put a planet to have the possibility of life forming.

            There's an interesting book, Rare Earth, by two University of Washington researchers who came up with the hypothesis that microbes [microscopic life forms] are probably all over the place. It's probably easy to get microbial life forms to occur, to evolve. The earth was formed five billion years ago and the first signs of life seem to occur about four billion years ago. So it didn't take very long for life to get started. But for the next three billion years it's just microbes. There's no more significant evolution.

            Then, in a very short span, for reasons we don't understand, something happens --- the Cambrian explosion --- where suddenly you get all these diverse life forms evolving. That was a hint that microbes might be easy to get but animal life forms --- multi-cellular, evolved, complex life forms --- that may be difficult to evolve, so it's very hard to say. Are we the only life in the universe? You look at all the planets and all the stars and you think there's got to be others out there. That's what I believe. On the other hand, if it's a one-in-a-trillion chance of having all the accidents you need to get life to occur, and you've only got a trillion planets, then you've run out of luck.

            City:When it was discovered a few years ago that there may have been microbes on Mars, people theorized that life on earth might have come from an asteroid.

            Frank: Yes, there's still a lot of discussion about that. Microbes could be very hardy. We know that microbes can live deep in rocks and we know that when asteroids hit Mars, rocks from Mars were blown over to the earth.

            City:What are the chances of finding highly evolved life?

            Frank: The issue of intelligence is another difficult one. Is intelligence selected for in evolution? We always think that's what happens; evolution always leads to intelligence. But there's no evidence that what we call intelligence is necessarily the end product of evolution. Given our own history --- we haven't been on the planet all that long and we do a lot of stupid things --- it's possible we may not last that long.

            I certainly believe that the universe is full of civilizations, because I want to believe it. That would be really cool. But from the scientific point of view, I don't have a whole lot of evidence. What's cool now is we're on the verge of being able to answer that question. NASA is designing telescopes called the Terrestrial Planet Finder that should be able to see if there are earth-like planets around other stars.

            If we can take a "spectra," meaning take the light and break it up into its component pieces, we could be able to detect things like methane. You have to have life to have certain chemicals present in the atmosphere. In 10 or 20 years, we can't go visit, but we may have some strong evidence for the fact that there are planets that have life on them.

            City:Will the Hubble eventually allow us to witness the Big Bang?

            Frank: With the Hubble we can't see back to the Big Bang because there's no light from the Big Bang that it can tune into. The Hubble can take us back to around a billion years after the Big Bang. If you look far enough back, the things that are emitting light haven't formed yet.

            Bob Williams, the former director of the Hubble, did a cool thing about 10 years ago. He pointed it at a region of sky that didn't have much in it and left the shutter open. The image he and others made is called the Hubble Deep Field, and it's one of the most famous pictures the telescope took. That representative little piece of sky turned out to be full of very old galaxies. What we are seeing in the Hubble Deep Field are galaxies in the epoch they were being put together.

City:Here are two unanswerable questions: What was before the Big Bang? And how does something come from nothing?

            Frank: On a certain level, the question of what was before the Big Bang is not amenable to the methods of science, which doesn't mean we suddenly jump into the realm of religion or spirituality. One of the things that is beautiful about what we have come to understand about the universe is that we have a kind of blinders on that came from evolution. We experience the world through three-dimensional space and then there's this fourth dimension of time. One thing we're realizing is that there may be a lot more dimensions than that; we just can't perceive them. That doesn't mean they're not there.

            So this question of beginnings and endings --- people ask what's at the end of the universe, do you come to a brick wall? --- can only make sense if you're thinking of space being this big shoebox into which all the stars were poured and there has to be an edge. What we've learned is, if you start thinking in higher dimensions --- like the games Picasso and the cubists were playing in paintings like Les Demoiselles d'Avignon, where you see all the sides of a woman's face at once --- once we recognize the potential for there to be more than three dimensions, suddenly, literally, you're no longer boxed in.

            City:How can there be more than three dimensions?

            Frank: We see each other, and what we see are three-dimensional shadows of four-dimensional creatures in the sense that we exist in time as well. This is what Einstein recognized. When you walk under a lamppost, first your shadow is long. Then, when you get under it, your shadow gets short, then long again. That shadow is a two-dimensional representation of what is really a four-dimensional creature.

            There's an example of how things can be so different going from low to high dimensions. Once we allow for the possibility that the universe might have 10 dimensions a lot of things change. The question of what came before the Big Bang may be something that science can never answer. Our ability to measure anything --- and that's what science is about, if you can't measure it, it's not part of science --- may stop at the Big Bang. But it's also possible that we may find ways in which things can kind of wrap back on themselves. The surface of a sphere doesn't have a beginning or an end.

            City:Just as the earth has no beginning or end, it strikes me that the universe, in an inverted sort of way, would also have no beginning or end.

            Frank: It's possible. One thing we've been doing since Einstein is thinking about the geometry of the universe in more than three dimensions. So it either lies at the edge of what our scientific understanding can tell about the world, or it's possible that when we add the possibility of extra dimensions, it will allow us to find ways in which the universe need not have a boundary in time. We know it doesn't have to have a boundary in space.

City:You alluded to Picasso. When I think of an astrophysicist crunching numbers, constructing computer models, or coming up with theories, it seems similar to an abstract art. Do you see a connection?

            Frank: Both art and science require an attention to detail and a reverence. Both ask of the practitioner an openness and a position of creativity, trying to take what is experienced someplace it hasn't been before. I try to beat out of my students the idea that science is this giant, picking up facts, putting them in its bag. Nothing can be further from the truth. The funny thing about science is the end product often has a highly dispassionate, impersonal view. I can't put a joke in a scientific paper. And even if I write alone, I say "we" carried out this experiment.

            But in doing science, you get passionate about it. I'm a theoretical physicist; I don't look through telescopes. There's a beauty to mathematics that is beyond words, a rapture that comes from the consideration of the way things fit together. I often think of mathematics, which is at the heart of all science, as being very much a poetic language. With poetry, one metaphor can embrace a whole set of nuances and subtleties in the same way that the equation for an ellipse has every possible ellipse in it.

            Art and science are very similar. When I took Shakespeare in college the professor asked why we were taking this class. I wrote, "I know why Einstein is great, but what makes Shakespeare great?" When I left I knew why. It's 500 years later and the stuff Shakespeare wrote is so true. That's why I love Joseph Campbell, his idea that myths carry from one culture to another, whether you're a tribesperson 5,000 years ago or a city dweller today. In science, the laws of physics are true anywhere in the universe.

            City:Your particular field of study is Planetary Nebulae.

            Frank: I study how stars are born and how they die. At the beginning and end states of their lives they tend to be surrounded by enormous clouds of gas either because they've blown them out or they're forming out of them. So I study what are called gas-dynamical processes. Each Planetary Nebula is a sun-like star at the end of its lifetime. These dying stars blow out incredible sculptures light years across. They're just beautiful. I use the equations of mathematical physics to try and understand why they have that shape and what it's telling us about how a star dies.

Next week: Adam Frank discusses the possibility of multiple universes, the theory of everything, and the joys of being a café astrophysicist.

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