Guesstimation

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.

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.

Lawrence Weinstein doesn’t know how many jelly beans are in this jar, but he has a very good guess. And it’s higher than you might expect. Weinstein, who teaches estimation at Virginia’s Old Dominion University, 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.

Fermi estimation, as such a method is known, helps experts decide if problems— from jelly bean counts to carbon counts—warrant further calculation. Precision isn’t always necessary. Take sea level rise. By assuming the thickness of the Antarctic ice sheet (1,000 meters) and dividing that by how many Antarcticas he thought would cover the Earth (30), Weinstein surmised that melting ice caps could raise sea levels at least 30 meters. Though USGS reports suggest a 73-meter rise (80 meters if you include Greenland’s ice sheet), his rough guess still predicts catastrophe. “I don’t need to refine that number,” says Weinstein. “I’m in Virginia Beach. Either way, I’m underwater.” —Oliver Uberti

Click here or the image for the answer.  Article featured in National Geographic Magazine