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Weinstein's 'Guesstimating' Featured in April Issue of National Geographic Magazine

Lawrence Weinstein, University Professor of physics at Old Dominion University and a researcher at the Thomas Jefferson National Accelerator Facility in Newport News, is usually on the trail of subatomic particles. So why does an article in the April issue of National Geographic magazine have him pondering over jelly beans?

The answer can be summed up in one word: "guesstimation." This is an art that he has been perfecting for some time now.

National Geographic illustrates its story-headlined "Mind Games"-with a colorful photo of a large jar of jelly beans, and the magazine explains how Weinstein would go about "guesstimating" how many pieces of candy there are.

"Weinstein…has a knack for solving problems with little data. His secret is more method than magic: Break questions into pieces, approximate, and use metric units for easier math," the article states.

Although he is respected internationally and has been elected a Fellow of the American Physical Society for his original contributions to the study of nucleon-nucleon correlations in nuclei, Weinstein is known, too, for his more whimsical applications of mathematics and physics.

In 2007 he began writing a column for The Physics Teacher magazine called "Fermi Questions," a term scientists use for the sort of questions that the renowned physicist Enrico Fermi could answer with quick applications of physical laws and numerical reasoning. At the first atomic bomb test, for example, Fermi dropped pieces of paper as the shock wave passed, and from the displacement of the paper and the distance to the explosion he accurately calculated the yield of the bomb.

Then, last spring, Weinstein and a mathematics colleague at ODU, University Professor John Adam, produced a book for the general public titled "Guesstimation: Solving the World's Problems on the Back of a Cocktail Napkin" ($20, Princeton University Press).

The book, which presents lighthearted problems for which ballpark solutions can be calculated by using plausible assumptions and arithmetic, has drawn broad media attention, especially from the Wall Street Journal's "The Numbers Guy" columnist. Also presenting stories about the book: Science magazine, Nature Physics, Games magazine, Business Week and BBC Focus Magazine. In addition to English, the book has appeared or soon will in Japanese, Chinese and Italian language editions.

The ODU professor believes that you don't have to be a Fermi to put physics to use. He is among the first of ODU's scientists to volunteer for outreach demonstrations for schoolchildren or to teach undergraduates. He says one of the best ways to get your head around physics-and to stay grounded in the physical world-is to apply principles governing matter, energy, space and time to what we see around us.

"I first encountered estimation questions in my high school physics course," he recalls. "I love them because they are a great way of applying physical principles to understand the universe."

ODU physics students also seem to enjoy estimation exercises. Weinstein teaches a seminar course, "Physics on the Back of an Envelope," that semester after semester is rated by physics majors as one of their favorite courses.

"One of the things I really like about teaching estimation," he adds, "is that there are frequently many paths to the answer, and I am often pleasantly surprised by students who have found a technique that I had never considered. The course also forces students to integrate what they have learned in previous courses. When confronted with an estimation question, they have to apply their knowledge of the world to determine which physical principles apply. They also have to figure out the necessary information not given in the problem."

This article was posted on: March 27, 2009

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