APS News

Simple Physics can be Useful in Understanding Real-World Issues

By Susan Ginsberg

David Hafemeister, author of numerous books on science policy topics and professor emeritus of physics at California Polytechnic State University, is currently in the middle of a series of seminars at physics departments showing students that one can apply physics to real-world issues.

He does this by simplifying the math, making assumptions, and doing quick and dirty calculations. His talks, as Hafemeister freely admits, "are full of 'spherical cows' to deal with issues like climate change." As part of this series, the Physics Department and the Security Policy Studies Program at The George Washington University teamed up to host a colloquium by Hafemeister in early September on the APS Boost Phase Intercept Study.

At the September 4 colloquium at GWU, Hafemeister gave the historical context of defensive missile systems beginning with Lyndon Johnson's negotiated defensive systems, through Ronald Reagan's Star Wars program, to the current situation which prompted the APS study on Boost Phase Intercept Systems.

Hafemeister took the colloquium audience through the calculations to determine the effectiveness of three systems discussed in the APS study: airborne lasers and ground- and space-based interceptors.

In discussing the airborne laser, Hafemeister pointed out the issue of overcoming turbulence as well as the uncertainty in the effects of shock and ablation on the target. "It's a hard physics problem," said Hafemeister after calculating to first order what the energy on the target would be coming from an airborne laser carried by a Boeing 747. "My guess is even the Pentagon doesn't know all the answers. I hope the DOD's Defense Science Board is asking hard questions."

With space-based interceptors some of the policy decisions are a simple matter of understanding basic physics, says Hafemeister. To intercept missiles from anywhere on the globe, you need either a lot of lighter interceptors, or fewer heavy ones.

Hafemeister easily illustrated the trade-off between weight and number of interceptors using a chart from the APS study and some simple physics equations.

The last system Hafemeister described was the ground-based interceptor. Although judgment calls are needed as to whether a particular interceptor was feasible, Hafemeister insists that GBIs can be understood using "Newton's laws and reasonable parameters." Hafemeister 's goal is to show the "system of decision" that is used by politicians, and how much of this system is basic physics in science policy questions.

Hafemeister ended his talk with an appeal to cooperative diplomacy: "You and I sitting in a bar over a napkin can get around any weapons system. What we really need to do is get people to talk to each other and be friends." Asked by an audience member whether this was a reference to getting physicists and engineers to work together, Hafemeister answered, "No, I meant getting nations to talk to each other, diplomatically. It's a political science concept."

Hafemeister's most recent book, "Physics of Societal Issues: Calculations on National Security, Environment and Energy" will be released in December of this year. The book is being published by Springer-Verlag and The American Institute of Physics Press.


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