Q&A/The mysteries of the universe—where it came from, what it’s made of—have intrigued Licia Verde since she was a young girl. Fortunately for her, she’s part of a research project that aims to answer just those kind of fundamental questions, and offer humankind a greater understanding of our vast, confounding universe.
“The amazing thing is that we can use scientific method, mathematics and physics to describe the whole universe.”
When Licia Verde was a young girl, a family friend bought her a book about the sky. Somewhere in that book was a chapter about cosmology—the science of studying the universe. And though the young Verde wasn’t quite sold on mathematics, she was instantly fascinated by cosmology’s fundamental question: Where did we come from?
It’s a fascination that remains with her to this day. Verde, an assistant professor in Penn’s Department of Physics and Astronomy, is among a handful of researchers participating in one of the science world’s most exciting projects: The Wilkinson Microwave Anisotropy Probe, or WMAP. The WMAP project, launched in 2001, aims to map out minute differences in so-called Cosmic Microwave Background radiation and, by extension, offer us a greater understanding of our universe.
The WMAP team in 2003 shocked the science world by producing a picture of the infant universe and, just last month, followed up that finding with new evidence of what occurred in the universe’s first trillionth of a second, when it expanded from submicroscopic to astronomical in size. The findings also suggest that 74 percent of the universe is composed of so-called “dark energy,” an unidentified force that is causing the universe to undergo yet another growth spurt.
We sat down with Verde recently to discuss what answers WMAP has turned up—as well as the many questions that remain.
Q. Broadly speaking, what is cosmology?
A. The first part is you want to understand how the whole universe is made, which is a pretty big question. It’s quite amazing, first, that you can even ask this question and, second, that you can actually answer it using the scientific method and that our brains can actually understand it. The second step is, if we can actually figure out how, more or less, the universe was actually made, can we ask the question: How did it all start? The amazing thing there again is that we can use scientific method, mathematics and physics as we know it here to describe the whole universe.
Q. How has the field changed over the past few decades? I imagine technology may have made a big impact.
A. Indeed, technology has really helped us a lot. The thing is, the tools are becoming more and more expensive, so [projects] need to involve many, many more people. Astronomy, up until now, has been a field where you can have a group of 15 or 20 people get together and do something that will have a big impact. In the next step, this is not going to be possible. There’s going to be a transformation, and it’s probably going to go in the direction that particle physics is going, where you have just one or two big experiments, and the whole community is involved in that.
Q. Is that a bad thing?
A. I don’t know. I think still there will be the opportunity for one single person to make an important contribution, but it’s probably not a field anymore where you can go over to the telescope like Hubble did and revolutionize the field.
Q. Were you always interested in space? Did you always know what you would do with your life?
A. No, actually. When I was young and I just started reading, some friend of the family, instead of giving me the book of Snow White gave me a book about the sky. I thought the chapter on the origins of the universe was really cool. But in Italy, by the time you get to middle school, you have to choose whether you‘re going to do something more literary or scientific. And I didn’t yet understand that mathematics described the physical world. For me, it was like, “1 plus 1 equals 2, or 3, who cares?” At that point I was directed toward studying literature—Greek, Latin, literature, stuff like that. Then, at a certain point along the way, I realized that … mathematics is the language of the world. It describes the world around it. You cannot say “1 plus 1 is 2 or 3, and I don’t care.”
Q. How did you become involved with WMAP?
A. I was at Princeton and was fortunate enough that the team asked me to join. I wouldn’t say no, because it was the occasion of a lifetime. ... The original point of the mission was to make a map of the Cosmic Microwave Background radiation with enough frequency coverage to be able to distinguish this radiation from the radiation from our own galaxy and to also have enough resolution to resolve the size of these “spots.” There is a fundamental thing that has to do with these spots—the size of the spots will tell you the size of the region causally connected when the universe was 380,000 years old. From that, you can learn about the geometry of the universe, the size of the universe, the age of the universe and so on. The mission ended up doing very much more.
Q. The most recent WMAP findings tell us that 96 percent of the universe is made up of matter that we can’t describe. Is that exciting, or frustrating?
A. I think it’s quite exciting. If we knew everything already, then we could go home, right?
Q. The findings say that so-called “dark energy” is causing the universe to expand. How can you explain this?
A. If I take something and throw it up in the air, because there is gravity, I can expect that thing to come back down. The same thing happened with the universe: The universe started off expanding, but then you’d expect it to slow down. But it happens that very recently, the expansion of the universe, instead of slowing down, has been accelerating. So it would be like if I took this ball and throw it, it starts decelerating as it goes up, then it starts accelerating again. This is the puzzle.
Q. When you say the universe began expanding “very recently,” what does that mean?
A. Very recently means that the first indication that expansion was accelerating came in 1998, but even before that, in hindsight, by looking at what we knew before then, we knew there was something that wasn’t quite right. But there just was not enough to actually introduce something as weird as “dark energy.” But when the supernova data came out, and you saw a graph that showed the universe had been accelerating … then you began to take [the idea] seriously. You couldn’t say, “Oh, maybe you had a glass of wine too many.”
Q. Given what you know today, how fully formed is the Big Bang theory?
A. The general paradigm is well formed but there are many things we don’t understand. For example, we believe that there was some period of accelerated expansion—similar to what’s going on now, but much more accelerated—that went on at the beginning of the universe. But how is that? What were the physics of that? If you can understand that, can we make connections to dark energy today? But when you want to describe the universe at that time … the universe is as a whole pretty massive, so you need to use general relativity, but it’s also very small, so you have to use some quantum mechanics. But when you try to put those things together, it makes no sense. So then you have to call in something else to try and make a more comprehensive description of what’s going on. There is the whole standard model of particle physics … and now all of these things are coming together. A few years ago [these fields] were completely separate and now they’re all coming together and trying to answer the same question.