and Nathaniel Lasry,. John Abbot College .... Lawrence Ruby, âTeaching special relativity without ... members to whom Lawrence Ruby refers, that in 2007 ...
Letters to the Editor
Our last point of contention is in methodology—not just in the classroom—but in our approach to thinkA rejoinder to Sobel’s coming about physics education. Sobel ment on “Are most people claims that there is no consensus on too dumb for physics?” the role and importance of problem 1 We read Michael Sobel’s response solving. Problem solving and questioning indeed have, for a long time, with much interest and appreciate been heralded as a standard goal of his enthusiasm and commitment to all education,2-4 science technolphysics education. Yet, we continue ogy engineering and math (STEM) to find that our goals and methods education specifically,5,6 and physics differ markedly. Foremost, because we do not agree that physics is a “dif- education in particular.7,8 Furthermore, there is significant evidence ferent category” of hard which is accessible to a select few (i.e., “a certain on how we might go about teaching sort of very bright student”), we can- problem solving (and questioning) in our physics courses (two review not agree that ordinary, nonscience articles9,10 are good places to start, students must be taught a different kind of physics. We object to the idea along with summaries of the field10 and PER-Central11). of two “types” of physics—one for As we engage in these explorations the layperson and one for the specialof what and how to teach, it is critical ist. Physics must have relevance for that we build on what is known in everyone. physics education and apply the same About reaching the majority of rigor, theory, methods, experiment, students with authentic forms of inquiry into the discipline, Sobel writes, and public critique of our educational practices that we do in the more tra“That’s just not the real world.” In ditional pursuits of physics. fact the inquiry-based and studentWe would like to end by echoing centered methods that we employ Michael Sobel’s acknowledgement are designed with the real world in of Karl Mamola, whose editorial vimind and do not require heroic efsion has enabled our community to forts to be effectively implemented. initiate a dialogue on what students What they do require is a change in one’s conception of instruction. Our should learn. goal is to reach a majority of students References and provide opportunities that are 1. Michael Sobel, “Response to ‘Are demonstrated to be expansive and most people too dumb for physproductive for the students and for ics?’” Phys. Teach. 47, 422–423 (Oct. society. Fortunately, in very diverse 2009). environments, we and the broader 2. How People Learn, edited by John D. physics education community, espeBransford, Ann L. Brown, and Rodney R. Cocking (National Academies cially those in physics education rePress, Washington, DC, 2000). search, have repeatedly demonstrated that we can educate the vast majority 3. A. P. Carnevale, L. J. Gainer and A. S. Meltzer (U.S. Dept. of Labor), of students in such a manner.
What Should We Expect Students to Learn?
Workplace Basics: The Essential Skills
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Employers Want (Jossey-Bass, 1990); Workplace Basics Training Manual (Jossey-Bass, 1991). 4. J. Dewey, Experience and Education (Kappa Delta Pi, Indianapolis, IN, 1938 and 1998). 5. US Law, 110-69, HR 2272, (2007). The America Creating Opportunities to Meaningfully Promote Excellence in Technology, Education, and Science Act (COMPETES); available at http://science.house.gov/ legislation/leg_highlights_detail. aspx?NewsID=1938. 6. Shaping the Future: New Expectations for Undergraduate Education in Science, Mathematics, Engineering, and Technology (Advisory Committee to the NSF Directorate for Education and Human Services, chaired by Melvin George, 1996); http://www. nsf.gov/publications/pub_summ. jsp?ods_key=nsf96139. 7. Czujko, Statistical Research Center of AIP, “Physics Bachelors as a Passport to the Workplace: Recent Research Results,” in The Changing Role of Physics Departments in Modern Universities: Proceedings of the ICUPE, edited by E. F. Redish and J. S. Rigden (AIP, 1997), pp. 213-223. 8. E. F. Redish, Teaching Physics with Physics Suite (Wiley, New York, 2003). 9. D. P. Maloney, “Research on Problem Solving: Physics,” in Handbook of Research on the Teaching and Learning of Science, edited by D. Gabel (MacMillan, New York, 1994). 10. L. Hsu, E. Brewe, T. Foster, and K. Harper, “Resource Letter RPS-1: Research in problem solving,” Am. J. Phys. 72(9), 1147–1156 (2004). 11. Physics Education Research Central, particularly Reviews in Physics Education Research; http://www.compadre.org/per/per_reviews/. Noah Finkelstein, Univ. of Colorado Eric Mazur, Harvard Univ. and Nathaniel Lasry, John Abbot College The Physics Teacher ◆ Vol. 47, November 2009
Letters
Teaching Special Relativity
system.” Actually, it is the rest energy equivalent of mass in any reference I was not one of those many AAPT system. The Russian theoretician Lev Okun has championed a campaign members to whom Lawrence Ruby these past 20 years for writing E0 = refers, that in 2007 received Elisha mc2, where E is the total energy of a Huggins’ booklet1 containing the free body, and E0 its rest energy. In first chapter of a physics textbook a 1989 Physics Today article, Okun espousing the new educational philosophy of teaching special relativity explains, “[I]t is evident that ... E0 = mc2 and E = mc2, are absolutely first in elementary physics. different. According to [E0 = mc2], Ruby’s recent paper proffers commass is constant and the photon is putations demonstrating that “all of massless. According to [E = mc2] m the principal results of special relativdepends on energy (on velocity) and ity theory can be obtained by simple 2 the photon has mass m = E/c2.”5 (See algebra.” He develops them in three sections titled: The Relativistic Dop- Ruby’s Eq. [11].) It appears eminently prudent and pler Effect, fr = f0 (1–v/c)1/2/(1+v/c)1/2; The Variable-Mass Formula, m/(1–v2/ worthwhile for Dr. Ruby (and Dr. Huggins), and perhaps the AAPT, to c2)1/2; and The Mass-Energy Equiva2 review the variable-mass and masslence Equation, E = mc . energy equivalence expressions for However, therein lie two longstanding topics of debate in the phys- use in future introductory physics textbooks of the 21st century. ics literature. For example, in Paul Tipler’s 1976 publication of Physics, References he states, “[T]he use of relativistic 1. E. R. Huggins, “Teaching Relativmass often leads to mistakes .... The ity in Week One,” based on the CD experimental evidence often cited text Physics2000, and “Principle of as verification that mass depends Relativity,” Chapter 1 of Physics 2000; on velocity can also be interpreted available at http://Physics 2000.com. as evidence of the validity of the as2. Lawrence Ruby, “Teaching special sumption that the force equals the relativity without calculus,” Phys. time rate of change of relativistic Teach. 47, 231–232 (April 2009). momentum.”3 And 10 years before, 3. Paul A. Tipler, Physics (Worth Publishin the first edition of Taylor and ers, Inc., New York, 1976), p. 686. Wheeler’s Spacetime Physics, they 4. Edwin F. Taylor and John Archibald aver, “[T]he quantity m is the mass Wheeler, Spacetime Physics (Copyas mass is understood in Newtonian right 1963, W. H. Freeman and Company, New York, 1966), p. 108. physics. Thus m is a constant, the 5. Lev B. Okun, “The concept of mass,” same at all speeds, all places, and all 4 Phys. Today 42, 31–36 (June 1989). times.” Ruby obtained “a relativistic James J. Carr mass” because he used the classical 129 Cranbrook Terrace, (Newtonian) momentum mv in his Webster, NY 14580 momentum conservation equation (his Eq. [6]). Editor’s Note: Correction to The second topic of debate surthe International Year of rounds the most famous equation Astronomy trading cards in the world, E = mc2, with which (series 1) included with the Ruby’s paper concludes (his Eq. September issue. [14]). He writes that it is “the enThe photo that appears on Annie ergy equivalent of mass in the rest The Physics Teacher ◆ Vol. 47, November 2009
Jump Cannon’s card is incorrect. A photo of Cannon appears below:
Credit: Harvard College Observatory, courtesy AIP Emilio Segrè Visual Archives
The incorrect photo was in fact Antonia Maury, who received the Annie Jump Cannon Award in Astronomy in 1943. Her bio appears below: Antonia Maury (1866-1952) Birthplace: Cold Spring, New York, USA
The niece of Henry Draper was instrumental in classifying the stellar spectra as part of the Henry Draper Catalogue, which was first published in 1897. However, Antonia Maury did not want to limit herself to simply sorting the spectra in the same old way. Her refinement of classifying spectral lines by width and intensity was later recognized by Ejnar Hertzsprung as a distinction between dwarf and giant stars. Maury was the co-discoverer of the first two spectroscopic binaries, Mizar (in Ursa Major) and Beta Aurigae, and was the first to calculate their orbits.
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