Category: Observation

This past week, while working on systematic uncertainty estimates for one of my research projects, I escaped to the SLAC library for a quiet but inspirational space in which to conduct my efforts. There was a particular moment when I needed to hit ENTER and wait for a program to execute and return some numbers. While waiting, I escaped my laptop and hit the bookshelves to browse.

In my browsing, I came across a book published through the Union of Concerned Scientists that preps scientists for interacting with the media. Titled “A Scientist’s Guide to Talking with the Media” and written by Richard Hayes and Daniel Grossman, the tips in the section on preparing for an interview were as applicable to going to Washington D.C. and doing science advocacy as they were for speaking with the reporter from your local paper.

It reminded me of the importance of libraries, of shelves of old books and new books waiting to be browsed. Access to information in structured but open ways is as critical to scientists as it is to the very functioning of our democratic system. In a timely way, this weekend the NPR program “On the Media” hailed Judith Krug, 40-year director of the American Library Association’s Office for Intellectual Freedom [1]. In the piece she quoted James Madison, who wrote,

A popular Government, without popular information, or the means of acquiring it, is but a Prologue to a Farce or a Tragedy; or, perhaps both. Knowledge will forever govern ignorance: And a people who mean to be their own Governors, must arm themselves with the power which knowledge gives.
—James Madison, letter to W.T. Barry, August 4, 1822

Amen to that. And hail libraries, for the serendipity and serenity they bring to the scientific process.

[1] http://www.onthemedia.org/transcripts/2009/04/17/08

As I’ve probably hinted with my previous post on baseball physics [1], I love the show “Mythbusters”. This past week, we had a new 2-hour episode focused on car demolition myths. In one segment, Adam and Jamie revisit an old myth that two semis, heading at one another at 50 mph and striking a compact car at the same time, can fuse metal to metal and make the compact car seem to disappear. They showed that the myth itself was not possible, despite perfect timing on the semi collision. They then tried to find out how much force would make the myth possible. What if the two trucks were driving at the speed of sound?

To do this, they put the car at one end of a track and fired a two-stage rocket sled at the car, achieving 650 mph before the sled hit the car. Their goal: to simulate the energy of two trucks smashing together at the speed of sound, with compact car stuck in the middle.

The same thought process that applied to the baseball myth applied here. The energy of the two trucks colliding is like two particles colliding head on with the same energy – the same velocity. Since kinetic energy is given by 1/2mv*v, where m is the mass of the object and v is the velocity of the object, the goal is to do the simulation with a fixed car and moving sled that simulates the energy of the two semis colliding head-on on the stationary car.

The energy of a head-on collision of two objects of equal mass is given by E = E1 + E2, where E1 and E2 are the kinetic energy of the two objects (trucks in this case). If the collision occurs in our laboratory as one object moving while the other is stationary, one needs to convert that energy into the “effective” energy of the same collision happening has a head-on collision. To get the same energy from the case where one object is at rest and the other is moving, you have to bring the kinetic energy of the moving object WAY up. Did the Mythbusters achieve this?

Let’s compute the ratio of the two cases: E_fixed/E_colliding = (1/2 M V*V)/(1/2 M v*v + 1/2 M v*v) = 1/2 V*V/v*v. This assumes the rocket sled had the same mass as one of the semis. We want the ratio to be 1, which indicates the simulation reproduces the target collision of a speed-of-sound collision.

Let’s run with that assumption. If the trucks were moving at the speed of sound and colliding head on, their speed would be v = 760mph, while the rocket sled was moving at V=650 mph. That gives us an energy ratio of these two cases of 0.4. That’s lower than they wanted. To really nail this myth, they would have needed to get the speed up to about 1000 mph on the rocket, assuming a sled with the same mass as a semi.

Let’s take the ratio of the masses of the semi and rocket sled into account. A semi weighs many tons – according to one estimate [2], an empty semi weighs about 7 tons. The rocket sled probably weighed no more than a few tons – lets say 2.

Our ratio then becomes 1/2 (M/2m) (V*V/v*v) = 0.05.

More way off. Eh. This is, of course, all math fun with kinetic energy. I love that the Mythbusters go from colliding beams to fixed target experiments, involving tremendous forces when they do so. While I might argue with their simulation of the colliding beam phenomenon, it sure is fun to watch a compact car vaporize when a rocket sled hits it at 650 mph.

Update (2009/04/14): this is what I get for blogging later at night. The equation for energy ratio in the case where the sled is not the same mass as a semi should have read:

(1/2 M V*V)/(1/2 m v*v + 1/2 m v*v) = (1/2) (M/m) (V*V/v*v)

I was wrong by a factor of 1/2 in the original equation (stupid factors of 2!). Thus, the energy ratio of the case they wanted to test to the case they did test was 0.1, not 0.05. So they were only off by a factor of 10, not 20.

[1] http://steve.cooleysekula.net/goingupalleys/2007/11/27/baseball-myths-fixed-target-vs-colliding-beams/

[2] http://books.google.com/books?id=uTiSu1mbBa8C&pg=PA435&lpg=PA435&dq=semi+tractor+trailer+weight+when+empty&source=bl&ots=mosMkE2enO&sig=ETAiEIVePTVK2rzKor-uAGn9a54&hl=en&ei=qLfiSaX0LZ38tgOWy-CtCQ&sa=X&oi=book_result&ct=result&resnum=1#PPA435,M1

Take the SLAC Library Survey

Not too long ago, the SLAC Library occupied a large space on the second floor of Central Lab [1], the heart of the administrative and research activities here at SLAC. Due to shifting priorities at the lab, and the need to renovate existing space in Central Lab for future experiments, the library was packed up and moved to new quarters. Those quarters are in the lobby of the Computing Center (Building 50). The amount of space lost between the old digs and the new digs is unimaginable and most of the library’s collection is now stored of reach of the average browser or library-goer.

The laboratory assembled a task force [2] to determine the fate of the library. My understanding is that this task force is deciding between several possible scenarios, such as an all-electronic library. My own opinion of this kind of choice is that it is devastating to an entire field of research. Before I go into the next paragraph of opinion, I invite you to take the SLAC Library Survey yourself – note that the very last page of the survey offers a big text box where you can express your own thoughts on why a library like SLAC’s is a useful resource (or not . . . your opinion is entirely your own).

Here is my opinion.

The United States is faced with a grim economic situation and part of restoring the strength of the U.S. economy is to make investments in education and science that train the next generation of innovators so that we can produce the discoveries that create new economic sectors or opportunities. Part of the U.S. scientific investment portfolio is its national laboratory system. SLAC is unique in this system in many respects, primarily because of the openness of the lab combined with its extremely close ties to Stanford University, just two miles down the road.

With the Visiting Scholar program here at the lab, even a lab user can gain access to Stanford Libraries. However, not having a library physically at SLAC does create a barrier between you and your resources. Not only that, but it’s not even clear to me that should all the resources of the SLAC library go to Stanford, there is any room to display them as a single collection for researchers to browse. The SLAC and Stanford Libraries have electronic journal access, but there are many books and conference proceedings available only in print.

I view the resource afforded by the SLAC Library as part of enabling the positive Black Swan [3]. The Black Swan is the unexpected event that completely changes the course of your thinking. It’s the swan that, when discovered, takes the induction that “all swans are white” and turns it on its head. These positive Black Swans are responsible for the general progress of science, and our field is no different. Having the ability to go looking for one thing in a library and find something totally unexpected on a neighboring shelf – something that changes the course of your thinking – in invaluable and currently unreproducable online.

There is also no way to quantify the benefit as too small – libraries cost money, for sure, but the value of even a single discovery enabled by happenstance library browse is priceless. Another way to look at a library is to wonder how many people have been able to determine that an alley is blind, just by looking over past work, before they march down that alley? How much wasted effort, spent reproducing a failed result, is prevented by a resource like a library? Can you quantify that, and put it on an Excel spreadsheet?

Digital publishing has enabled a glut of information to be available at your fingertips. The problem is that, unlike a library, it’s not ordered in a useful way. The library cataloging system has not yet been replaced by keywords, and there is no substitution for the human eye and its ability to browse. SPIRES is nice, but when I use it I find half the time I get too much information and the other half I get too little. Digital searching takes a glut of information and returns a glut of information, while the library smooths out the fluctuations and allows the mind to focus on a new idea, an interesting title, an old undigitized book.

I worry that at a time when innovation is so critical to the U.S., SLAC is considering disposing of an engine of innovation to its research community. When reading “Beamtimes and Lifetimes” by Sharon Traweek, I was struck by her description of the SLAC library. She noted that it was never that busy, that there were people reading or napping, but not too many of them. That level of usage hasn’t changed much since the 1970s, when she wrote her description; yet, SLAC has been involved in major, Nobel-prize-worthy discoveries in that time and, I believe, should continue to do so. I worry that once we cast away a fundamental resource like a library, used frequently or not, we’ll lose even the infrequent browsings that create rare, Nobel-prize-winning work.

[1] http://steve.cooleysekula.net/blog/2008/06/26/i-remember-libraries/

[2] http://today.slac.stanford.edu/a/2009/03-30.htm

[3] Taleb, Nicholas Nassim. “The Black Swan: The Impact of the Highly Improbable”