Wednesday, April 16, 2008

Spirit of Saint Louis

Hi, I'm Gabe Popkin. I'm new to the Physics Buzz, but not to physics. I got an undergraduate degree in physics from Wesleyan University in 2003 and now I work in the APS Education Department, mostly on a project to help physics faculty recruit and prepare future teachers. I am also involved in creating educational materials based on cutting-edge science research.

I just got back from the APS April Meeting in Saint Louis, where I spent much of my time manning a booth for an APS-led project called the Physics Teacher Education Coalition, or PTEC. PTEC is a group of around 110 universities, colleges, and one national lab at which at least one faculty member has taken an interest in working with some of tomorrow's physics teachers. The Coalition began in May of 2003 as an outgrowth of the PhysTEC project, which funds a smaller number of universities to develop strong teacher preparation programs that can serve as national models.

So you may imagine it can be a hard sell to get physicists to talk about teachers at a research-driven event like the April Meeting. Indeed, one guy, when I asked him whether he was interested in what APS does in education and outreach, flatly said "Not at all," and hobbled off. Others were perhaps more respectful, if no less apathetic. But the truth is, many if not most physicists are concerned about the state of physics education in America's schools, and rightly so. The world and the workplace are becoming more technical every day, and there is plenty of evidence suggesting that many of our country's students are not getting the preparation they need to keep up. And so APS has made it a top priority to engage its members in preparing the next generation of physics teachers, who will in turn prepare the next generation of physicists.

Here is Assistant Director of Education Monica Plisch talking to a meeting attendee about teacher preparation.

Of course I was able to get away from the booth for a little while to catch some of the other action. Probably the most interesting talk I heard was Burt Richter's presentation of some of the findings of the upcoming APS Panel on Public Affairs' report on energy efficiency. Did you know that if you take the integral over the cost to society of all the CO2-saving technologies we can implement right now, it comes out to just about zero? Yep, this plot of carbon savings versus cost from McKinsey and Company shows the carbon savings of various technologies versus cost. So there is nothing economic stopping us from taking these steps; politics may be another story, though. The total potential savings is over 3 gigatons of CO2 per year. I have no intuition for a gigaton of carbon dioxide, but currently we emit 7.2 gigatons/year, so 3 is significant, especially considering projected growth of 2.5 gigatons/year by 2030. I also found it interesting that the most costly carbon-saving innovation - car hybridization - seems to be among the most popular. Is this perhaps because your car makes a very clear public statement about your commitment to saving the world that you just don't get from, say, promoting coal mine methane capture?

Of course you can't visit Saint Louis without marveling at the gigantic inverted catenary curve that stands by the river, and just a few minutes' walk from our hotel. I became slightly obsessed with this shape, and searched the internet for proof that the catenary is the most beautiful curve. At least I hoped to find a poll similar to those that have identified Euler's identity as the most beautiful theorem in mathematics. But no such poll has been conducted, so I will simply assert it without proof, and leave it to the neurobiologists to find the region of the brain that releases happy chemicals when it sees the catenary, or the golden spiral, or any of those other famously pleasing forms.

The catenary is the shape that minimizes the potential energy of a hanging chain, and when inverted and used to form an arch, it gives a structure that is subject to no shearing forces, only compression. I thought surely if an inanimate thing like a chain could assume this curve without the slightest intelligence, I, with my mighty human brain, should be able to calculate it. But the solution is surprisingly nontrivial, and my calculus of variations being rusty, I defer the proof until a later date. Suffice it to say that I secured a piece of paper from the unamused receptionist in the visitor center that informed me that

y = -127.7 ft * cosh(x/127.7 ft) +757.7 ft.

where x = 0 is at the center of the arch. Naturally.

Being at the base of such a large geometrical form is disorienting in a way that is both unexpected and pretty cool. It also makes for interesting photo opportunities, and I leave you with a few pictures I took from various positions. For a more whimsical take on the arch's mathematics and history, I encourage you to read this post from Cocktail Party Physics.


  1. “Knowledge is NOT power, it IS knowledge;
    just imagine Stephen Hawking in a
    room filled with hungry mosquitoes.”