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Last update - 19:23 05/03/2008 A conversation with Yossi Nir By David B. Green Tags: Yossi Nir  Yossi Nir, a professor of physics at the Weizmann Institute of Science, is the coauthor of "The Mystery of the Missing Antimatter" (Princeton University Press, 278 pages, $29.95). His collaborator on the book was physicist Helen R. Quinn, a professor at the Linear Accelerator Center at Stanford University. On the simplest level - although there is nothing simple about the subject matter - the book (with illustrations by Israeli cartoonist Rutu Modan), aims to answer the question of why the universe has such a wide disparity between the observed quantities of matter and antimatter, since by all indications, the two were created in equal quantities at the time of the Big Bang, some 14 billion years ago. Together with Quinn, the 53-year-old Nir, who was educated at the Technion and at Weizmann, uses the occasion to explain what is meant by "antimatter," and to review the advances of physics over the past century, during which time scientists have confirmed experimentally a whole set of theories to explain the history of the universe and the relationship of energy to matter. Readers are liable to go through the book in a state of constant dropped jaw, so overwhelmingly vast, on the one hand, and tiny, on the other, are the sizes, distances and lengths of time described therein. Haaretz spoke with Yossi Nir by e-mail from Rehovot. . . . Advertisement Can you tell readers of Haaretz just what "antimatter" is, and roughly, what your answer is to the mystery of why there is so little of it left today? Every subatomic particle (electron, proton, neutron) has an antimatter twin with opposite charges. For example, the electron, which is negatively charged, is twinned with the positively charged "positron." We produce positrons, antiprotons and antineutrons in our laboratories, but they seem to be missing from the universe at large. In the laboratory, particles and their matching antiparticles are always born together, and they also die together, being annihilated in a flash of radiation energy. But herein lies the puzzle. If they are born together, the early universe must have had equal amounts. So why did antimatter disappear? And, if they die together, how did matter survive? In the 75 years that have passed since the first antimatter particles were observed in experiments, much progress has been made in understanding the answer. The principle behind the solution is a subtle difference in the laws of nature that apply to matter and antimatter, respectively. Such a difference created a minuscule asymmetry between the number of particles and antiparticles in the early universe: For every billion or so antiparticles, there have been one billion and one particles. This tiny excess is all that is needed to explain the complete domination of matter in the present universe. But, while the principle has been understood, the puzzle remains. The required difference in the natural laws for matter and antimatter must come from processes that are different from anything that we have measured in our experiments. But what processes are these? Nobody knows for sure. The possible culprits are elusive particles called neutrinos, and experiments are carried out to understand their profile better. Despite the very clear writing in your book, there's no way to get around the fact that this material is tough. Why do you feel it's important for educated people to have a basic understanding of particle physics? The questions that particle physics aims to answer are deep and intriguing, questions that lie at the very basis of our existence. To understand who we are, we must also understand what the universe is, and what natural laws dictate its evolution. Human beings, with a life span of, say, 100 years, and whose "messengers" have barely left our tiny solar system, are able to explore with solid scientific methods things that happened at the edge of the observable universe, some 13 billion light years away, and understand events that took place when the universe was less than a millionth of a millionth of a second old. At the same time, we understand the laws of nature that are at work at distances as small as a billionth of a billionth of a meter, an unimaginably small distance, compared to the ones relevant to our everyday experiences. I think it's important to understand how far and deep the human mind has reached. But, beyond the issue of importance, it is clear to me that to have some knowledge and understanding of these issues is also very enjoyable and intellectually rewarding. You're in Israel, and Helen Quinn is in California. How did the two of you come to be writing this book together, and what was the division of responsibility? Helen and I collaborated on scientific projects for quite a few years before the idea that we should try to write a popular book arose in our conversations. I had had some experience giving popular lectures on particle physics. I could recognize the curiosity of the audience and the fact that most were unfamiliar with some very basic facts in particle cosmology, facts that are, by the way, not so hard to explain. Beyond her research interests, Helen was also working on issues of science education for many years. It's given her a unique understanding of how to communicate scientific knowledge to intelligent and educated non-scientists. We thought not only about filling a gap in education, but also about sharing the joy of physics with our potential readers. Each of us had concrete ideas about how to explain some parts of the puzzle. So we started by having each of us write a first version of the respective chapters. Then we exchanged the chapters and, over six years, modified and improved them. Helen and I were good friends even before the book. Actually, the book would have been impossible had this not been the case. But the writing also made the two families - Helen?s husband and two children, and my wife and four children - good friends. Indeed, the sight of Dan, Helen's husband, playing soccer with my three boys in the backyard of their Lake Tahoe house, while Helen and I were working indoors, is one of my fondest memories from the period of writing the book. How did you become involved in physics to begin with, and do you think that schools in Israel today offer enough basics to entice young people to study pure science that won't necessarily lead to a high-paying job in high-tech? In retrospect, I think that my choice of physics has its roots in high school. Mario Livio, currently an astrophysicist at the Hubble Space Telescope Science Institute [in Baltimore], was my physics teacher then. I often think I chose to study the subject not because I knew what it would be like to do physics, but because Mario was such a charismatic teacher. But whether I chose physics for the wrong or for the right reasons, I never had any regrets. Whether the basic science education is satisfactory depends to large extent on the quality of specific teachers. What seems to be lacking quite generally, and is perhaps hard to do, is delivering the sense that science is not only a technical challenge, but a very wonderful experience. As a profession, I can hardly imagine a more rewarding one. That said, I must (happily) admit that the physics faculty in Weizmann Institute gets brilliant, enthusiastic and creative graduate students year after year. Where there is clearly a problem is in a later stage. Four of my ex-students are now abroad: at Berkeley, Cornell, Stony Brook and Princeton. None has so far returned to Israel. Without recognition of the importance of scientific research by the government, it cannot survive at its present high level. Your book drives home something we already know - just how very very vast the universe is, and how infinitesimally small our solar system and planet are, in comparison. Has your study of the subject given you any insight into whether there is intelligent life elsewhere in creation? This is not a question that I personally have worked on. At least in principle, it is a question within the realm of science, and I can look at some aspects of it. One question is the probability that, given appropriate physical conditions, the evolution of self-replicating molecules would occur. The likelihood of this has to be extremely small. Another question is the number of locations in the universe with sufficiently rich environments for such a process to be able to occur. This must be a very large number. The final probability for life existing elsewhere, then, would be the product of an incalculable small number with an incalculable large one. I suspect the answer is that, in all likelihood, Earth is not unique in supporting life. However, the physical distances between such systems would be so large that we would be unlikely to ever detect any evidence of other life. How does your work affect your approach to the idea of God? Are the rules you have spent your life studying sufficient to have created themselves and the universe you describe in the book - or do you think it required a master planner? Let me first say I see no contradiction between being a physicist, even one who studies cosmology, and being religious, if one accepts that science and religion are trying to answer different questions. What I personally have taken from science is the belief in facts that have been tested in experiments, and being skeptical otherwise. Indeed, science starts from a postulate that there are universal laws of nature that do not change from one place to another or from one time to another. This idea has passed a lot of tests. Claims of miracles - events outside these laws - are generally not testable because, by definition, such events are not replicable. As noted in my answer to the previous question, I see no reason to assume any plan; life could have evolved, in principle, from random chemical events. As for the question of whether a God of creation was needed to set the universe in motion and set up the rules, this is outside science, and my personal view on it is as good (or bad) as anyone else's. Bookmark to del.icio.us   UN hushes Human Rights Council observes moment of silence for Gaza 'martyrs.' Hitler's sign Document shows that British spies hired a flamboyant astrologer in World War II.

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