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Essay
Spore* Series winner

Open Source Physics

Science
25 Nov 2011
Vol 334, Issue 6059
pp. 1077-1078
Scientists routinely use computer modeling and computation in innovative research,including predicting the nature of He4 at extremely low temperatures and the impact ofhuman activity on climate. Why does computer-based modeling remain absent from manyeducational programs?
The Open Source Physics (OSP) project, www.compadre.org/osp/, seeks toenhance computational physics education by providing a central Web site containingcomputer modeling tools, simulations, curricular resources such as lesson plans, and acomputational physics textbook that explains the pedagogic simulations' algorithms(1). Our resources are basedon small single-concept simulations packaged with source codes that can be examined,modified, recompiled, and freely redistributed to teach fundamental computationalskills. Students at all levels will benefit from these interactive simulations bylearning to question and assess the simulation's assumptions and output.
Students who learn physics concepts via static pictures may be led to constructincomplete or incorrect mental models that hamper their understanding of physicalconcepts. Our ready-to-run simulations and tools for developing new simulations helpstudents visualize situation and better understand abstract concepts through aresearch-proven pedagogical process called the Learning Cycle (2, 3).
In the first phase of a simulation-based cycle, “Exploration,” studentsexplore questions or a problem situation about a phenomenon or concept and makepredictions about the outcome. This phase encourages students to think about the subjectmatter, become curious about it, raise questions, and use prior knowledge in theconstruction of a hypothesis about possible simulation outcomes. Students may then testtheir hypotheses using an experiment or demonstration together with a simulation. Duringthe second phase, “Invention,” the teacher guides students through theintroduction and development of essential knowledge. Students may begin by sharing theirobservations and ideas from the exploration phase. The teacher then uses simulations todevelop the content knowledge and to introduce relevant vocabulary. In the final“Application” phase, the teacher poses new problems or situations for thestudents to solve, based on the exploration that they refined in the second phase. Thesame simulation can be used in more than one Learning Cycle phase or can be modified andextended once teachers are familiar with the OSP computer-modeling tools.
Dynamic modeling.
Middle school students launching bottle rockets for Tracker video analyses.
CREDIT: WOLFGANG CHRISTIAN
Our simulations require student interaction. When solving physics problems, novicestudents tend to reach first for an equation to apply rather than trying to understandthe underlying physics concepts. In well-designed simulations, physical quantities, suchas force or field strength, are not given. Instead, they must be determined by runningand observing the outcome and by interacting with the simulation to make measurements.By determining relevant information early in the problem-solving process, students mustunderstand the conceptual underpinnings of the problem. Our simulations also usemultiple representations to depict information, as students learn best when they seeideas presented in different ways, for example, as time-based graphs and tables (4).
The transition from working with interactive simulations to computer-based modeling canbe especially challenging for students. In addition to learning a programming language,students must master a range of techniques, such as compiling and linking with graphicsand numeric libraries, before being able to create a running computer program. Tominimize these difficulties, OSP has developed a number of free modeling, authoring, andanalysis tools. Two of these tools are Tracker (5) and Easy Java Simulations (EJS).
The Tracker video analysis and modeling tool enables students to create particle modelsbased on kinematics or Newton's laws and to compare the model's behaviordirectly with that of real-world objects, such as the water rocket shown in the firstphoto, captured on video (5).Tracker's model builder provides an introduction to dynamic modeling by making iteasy to define and modify force expressions, parameter values, and initial conditions,while hiding the numerical algorithm details. Because Tracker particle modelssynchronize with and draw themselves right on the video, students can test their modelsexperimentally by direct visual inspection. A browser in Tracker enables users to openvideos and models directly from the OSP and other Web sites.
The Easy Java Simulations (EJS) modeling tool organizes a computer model into four parts:the computation, which implements the phenomena under study in terms of variables thatdescribe the state of a system and algorithms that change those variables; the control,which defines actions that a user can perform on the simulation; the view, which shows agraphical representation of the model and its data; and the description, which providesan opportunity for the author to document the model's theory, assumptions, andrange of validity.
A typical phenomenon that is studied in introductory physics is the harmonic oscillator.A simple algorithm that teaches both the physics and calculus of harmonic motionfollows:
The first statement says that acceleration is caused by a spring force, the second saysthat the acceleration affects the velocity, and the third says that the velocity affectsthe position. Very little additional code is needed to produce a simulation, as the userinterface is constructed by dragging and dropping buttons, graphs, and tables from apalette onto the view. Basic programming syntax is taught while students focus onimplementing ideas as algorithms and on interpreting the model's output.
After a model is built, its supplemental graphics and description pages are packaged fordistribution. The resulting file is a stand-alone application that does not require EJSand can run on any computer with a Java virtual machine. Because every simulation isdistributed with its source code, users can examine, modify, and redistribute the modelwith minimal effort. Right-clicking within a running simulation displays a menu with anoption to extract and copy the source code into the local computer's EJS workspace.This allows teachers to ask students to modify and repackage a model, thereby creating ateacher-student feedback loop that supports the Learning Cycle.
Skill building.
A South African OSP workshop participant presenting results from a moleculardynamics model.
CREDIT: WOLFGANG CHRISTIAN
The OSP Web site allows teachers to pick their level of computational engagement from arange of possibilities. Teachers may use and modify existing simulations, distributeready-to-run simulations to students for visualization purposes, distribute partiallyconstructed or flawed models that students must edit and return, or construct broadassignments for students to create models from scratch (6).
The OSP Collection currently contains more than 400 primary materials, and many entrieshave multiple support documents. For example, the “Roller Coaster” modelincludes three ready-to-run simulations, a lesson plan and student worksheet, an appletpage, and the source code. A tabbed panel provides annotations, including thismaterial's alignments to the AAAS Benchmarks for Science Literacy and the NationalScience Education Standards. As with any good library, the documents are cataloged withstandard metadata and can be found via search criteria such as subject, author, level,and keyword.
Despite its original focus on upper-level college physics, the OSP Collection servesthousands each month. During March 2011, we served 10,000+ visitors with 5000simulations, an increase of 32% over March 2010 traffic. User loyalty is increasing aswell; over 2500 different users visited at least eight times between January and March2011, an 80% increase from January to March 2010 and an indication of the project'sincreasing visibility.
The OSP Web site is based on the ComPADRE Digital Library infrastructure and supportspeer-reviewed user submissions of simulations and text resources, personal resourcecollections, and discussion forums where users can post questions and discuss lessonplans. Because ComPADRE is itself a part of the National Science Digital Library (NSDL),OSP is able to broadly disseminate records for its content to partners usingstandardized educational metadata. The OSP Web site also provides federated access toresources from other projects including the NSDL.
Designing and building models that intrigue and educate without overwhelming has beenchallenging. We have learned that a simple set of buttons to start, stop, and reset asimulation followed by a small number of editable parameters, such as the length of apendulum, helps to guide inquiry. Additionally, we learned that “freely availableon the Internet” is not enough. The process of establishing and cultivating anactive international community that shares new simulations takes an ongoing commitment.Meeting face to face and developing personal relationships with faculty are essentialfor obtaining new simulations and have proven to be at least as important as having anattractive Web site. Thus, we give a number of workshops (see the second photo) everyyear for novice and expert modelers alike. These workshops help faculty to form andrefine the skills needed to create simulations and implement modeling in theirclassrooms. For those unable to attend, we offer online video tutorials to help developcomputational modeling skills.
Computational modeling tools allow students to understand a model and its computationalprogramming rather than working on creating its user interface. Paraphrasing RichardFeynman, we have learned that if we cannot reduce a model to an algorithm, we do notcompletely understand it.

7

We thank B. Mason, M. Belloni and D. Brown for invaluable help with our project. Thiswork was funded by NSF, the Spanish Ministry of Science, and the Seneca Foundation.The ComPADRE Digital Library is sponsored in part by NSF grants DUE-0226129,DUE-0532798, and DUE-0442581

Footnote

*
SPORE, Science Prize for Online Resources in Education;www.sciencemag.org/site/special/spore/.
About the authors
Wolfgang Christian is the Brown Professor of Physics and chair of thePhysics Department at Davidson College, a Fellow of the American Physical Society(APS), past chair of the APS Forum on Education, and president-elect of the NorthCarolina Section of the American Association of Physics Teachers. FranciscoEsquembre is associate professor of Mathematical Analysis at theUniversity of Murcia, Spain, and dean of its Faculty of Mathematics. He teachesmathematical analysis and numerical algorithms of continuous and hybrid systems andis the creator of Easy Java Simulations. Lyle Barbato is the technicaldirector of the ComPADRE Digital Library and has developed the OSP Web site'stools and support services. Christian, Esquembre, and Barbato have beencollaborating since 2005 on the development and distribution of interactivecomputer-based material.
CREDIT: W. CHRISTIAN PHOTO BY BILL GIDUZ; F. ESQUEMBRE PHOTO BY ARACELIESQUEMBRE; L. BARBATO PHOTO BY ANNA BARBATO

References and Notes

1
Gould H., Tobochnik J., Christian W., An Introduction to Computer Simulation Methods(Addison Wesley, Boston,MA, 2006).
2
Karplus R., Butts D. P., J. Res. Sci. Teach.14, 169 (1977).
3
Jackson J., Dukerich L., Hestenes D., Sci. Educ.17(1), 10(2008).
4
Rieber L. P., Tzeng S., Tribble K., Learn. Instr.14, 307 (2004).
6
Cox A., Junkin W. F., Christian W., Belloni M., Esquembre F., Phys. Teach.49(5), 273(2011).

About the authors

About the authors
Wolfgang Christian is the Brown Professor of Physics and chair of thePhysics Department at Davidson College, a Fellow of the American Physical Society(APS), past chair of the APS Forum on Education, and president-elect of the NorthCarolina Section of the American Association of Physics Teachers. FranciscoEsquembre is associate professor of Mathematical Analysis at theUniversity of Murcia, Spain, and dean of its Faculty of Mathematics. He teachesmathematical analysis and numerical algorithms of continuous and hybrid systems andis the creator of Easy Java Simulations. Lyle Barbato is the technicaldirector of the ComPADRE Digital Library and has developed the OSP Web site'stools and support services. Christian, Esquembre, and Barbato have beencollaborating since 2005 on the development and distribution of interactivecomputer-based material.
CREDIT: W. CHRISTIAN PHOTO BY BILL GIDUZ; F. ESQUEMBRE PHOTO BY ARACELIESQUEMBRE; L. BARBATO PHOTO BY ANNA BARBATO

Information & Authors

Information

Published In

Science
Volume 334 | Issue 6059
25 November 2011

Submission history

Published in print: 25 November 2011

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Acknowledgments

We thank B. Mason, M. Belloni and D. Brown for invaluable help with our project. Thiswork was funded by NSF, the Spanish Ministry of Science, and the Seneca Foundation.The ComPADRE Digital Library is sponsored in part by NSF grants DUE-0226129,DUE-0532798, and DUE-0442581

Authors

Affiliations

Wolfgang Christian [email protected]
Davidson College, Post Office Box 6926, Davidson, NC28035, USA.
Francisco Esquembre
Departamento de Matemáticas, Universidad deMurcia, 30071 Murcia, Spain.
Lyle Barbato
American Association of Physics Teachers, One PhysicsEllipse, College Park, MD 20740, USA.

Notes

Author for corespondence. E-mail:[email protected]

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