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INSIDE SCIENCE RESEARCH --- PHYSICS NEWS UPDATE The American Institute of Physics Bulleting of Research News Number 878, December 2, 2008 www.aip.org/pnu

LEADER OF THE PACK. A new study shows why it’s sometimes better to stay out front.

Lance Armstrong, the cyclist who won the Tours de France seven times, often came in first because he spent so much time in second. That is, he would regularly pedal right behind a teammate whose job was to obligingly break up the stream of oncoming air, making it easier for Armstrong to save his own energy for a sprint later on. Stock cars also often maneuver to be in the draft of the car in front, thus reducing drag. A new study, however, suggests that this strategy of staying right behind a leader can backfire.

Bikes and stock cars are rigid bodies which cast a definite wind shadow. But if the object out front is a flapping body, such as a wiggling fish, a waving flag, or a bird beating its wings, then the disturbed flow set up by the flapping can increase, rather than decrease, aerodynamic drag for the follower. Not only does the follower experience more drag---forcing him to expend more energy go keep up---but the leader feels less drag.

This hypothesis is difficult to test on living animals such as birds or fish so two scientists performed an experiment with tiny waving flags. Leif Ristroph of Cornell University and Jun Zhang at New York University used two flags. Instead of a stream of air they used a flowing soap film that allowed clear images to be taken of the complex patterns set up when the fluid comes past the flags.

The result was surprising. Not only was the drag for the following flag made worse by the swirling fluid, but the measured drag felt by the leader was reduced, by as much as 50 percent, below the drag it feels when it is by itself. This is because the commotion set up by the following flag can mitigate the drag felt by the leader.

Zhang says that it’s too early to confirm that for some animals-such as migrating birds and schools of fish-being the leader of the pack is better because it reduces the energy needed to counteract drag. So far the experiment has been carried out with two flags and with six flags, and Zhang and his colleague would like to study their ideas with real animals. He believes that his results might have industrial applications, where reducing energy input is almost always a good thing. P.F. Schewe
( Physical Review Letters, 7 November 2008))

WHAT PRESIDENT-ELECT OBAMA NEEDS TO KNOW ABOUT PHYSICS. Nuclear and biological terrorism, energy, and climate are among the top topics.

Even scientists can hardly keep up with the influx of new research discoveries. So how can the president of the United States, with a blizzard of issues to deal with daily, expect to stay informed on scientific and technological developments that have an impact on society? Richard A. Muller, a professor at the University of California at Berkeley, addresses this problem in his new book, "Physics for Future Presidents." The book is divided into five large topic areas which essentially define the hottest issues of today: terrorism, energy, nukes, space, and global warming. Muller believes that anyone who strives to be a world leader needs to possess a core of knowledge in these areas.

Muller's book is based on a course he's been teaching at Berkeley for years, so he's had plenty of time to think about what the world leader needs to know---at least that part of knowledge pertaining to the material world. Voted the best course on campus, Muller's class, "Physics for Future Presidents" uses no equations or detailed mathematical description. Instead it imparts a commonsense, but accurate, appreciation of certain technological hazards and opportunities.

For example, Muller believes the president should know about radiation levels (it's the accumulative dose that is medically important), about the difference between nuclear fission and fusion explosions (the latter are much more powerful), about the relative energy content of various substances (gasoline, and even cookies, have more energy per weight than TNT), and about the relative cost of electricity obtained from batteries used in cell phones, computers, and automobiles. The president must be able to intelligently absorb information about the impact of human technology on climate, and to know that no single unexpectedly hot or cold day denotes a significant indicator of things to come.

The president can't afford to learn about such things as the danger from radiation at the last minute, argues Muller, because in certain circumstances, every second counts. Consider, for example, the detonation of a dirty bomb, in which an ordinary (non-nuclear) explosion spreads radioactive materials. Fatalities, property damage, and even residual radiation, would likely be very small. "The biggest danger from a radiological weapon is the misplaced panic and overreaction that it would cause. A dirty bomb is not really a weapon of mass destruction, but it is potentially a weapon of mass disruption," Muller says. Allocating resources during a crisis---military, medical, emergency, and engineering---requires quick and shrewd thinking.
Muller views physics as the "liberal arts of high technology," insofar as physicists are trained to solve problems in a broad category of topics, many of them relating to the very topics---such as energy and nuclear issues---that form the backdrop to numerous national-security concerns. This is probably why so many presidential science advisors have been physicists.

Science advisors have been losing the clout they once had, Muller believes, because they---and scientists in general---are perceived as a special-interest group, with their goal being greater federal support for science. A good presidential science advisor, Muller argues ironically, should not do all that much advising. Instead she or he should act as an early alert system informing or educating (but not lobbying) the president on science and technology issues and their possible impact.

Muller has extensive experience on rendering government-requested science advice. For many years he was a member of the "Jasons," an organization of leading scientists who meet for a month or more each summer to study specific subjects---most of them relating to national security---of interest to the Pentagon or other federal agencies. This work, Muller says, taught him the value of asking lots of dumb questions and of not necessarily trusting all the things he was told by experts.

Test your own presidential science knowledge. Nature magazine featured a set of questions from Muller's class on its website: www.nature.com/news/specials/climatepolitics/index.html

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